LIMONENE

Limonene is a chiral molecule, and biological sources produce one enantiomer: the principal industrial source, citrus fruit, contains d-limonene ((+)-limonene), which is the (R)-enantiomer. Limonene has benefits over many other solvents due to its excellent solvency, high degree of biodegradability and derivation from renewable resources. Limonene has a characteristic odor of oranges and is most often used in the manufacture of bio-based cleaning compounds, and as a flavor and fragrance additive

 

EC / List no.: 227-813-5
CAS no.: 5989-27-5
Mol. formula: C10H16

EC / List no.: 227-813-5
CAS no.: 5989-27-5
Mol. formula: C10H16


d-Limonene
d-Limonene is extracted during the production of orange juice.
d-Limonene has a characteristic odor of oranges and is most often used in the manufacture of bio-based cleaning compounds, and as a flavor and fragrance additive.
d-Limonene has benefits over many other solvents due to its excellent solvency, high degree of biodegradability and derivation from renewable resources.

CAS Number: 5989-27-5

Limonene is the oil extracted from the peels of oranges and other citrus fruits.

People have been extracting essential oils like limonene from citrus fruits for centuries. 
Today, limonene is often used as a natural treatment for a variety of health issues and is a popular ingredient in household items.

However, not all of limonene’s benefits and uses are supported by science.

This article examines limonene’s uses, potential benefits, side effects, and dosage.

What is limonene?
Limonene is a chemical found in the rind of citrus fruits, such as lemons, limes, and oranges. 
It is especially concentrated in orange peels, comprising around 97% of this rind’s essential oils.

It’s often referred to as d-limonene, which is its main chemical form.

Limonene belongs to a group of compounds known as terpenes, whose strong aromas protect plants by deterring predators.

Limonene is one of the most common terpenes found in nature and may offer several health benefits. 
It has been shown to possess anti-inflammatory, antioxidant, anti-stress, and possibly disease-preventing properties.

SUMMARY
Limonene is an essential oil found in citrus fruit peels. 
It belongs to a class of compounds called terpenes.


Common uses of limonene
Limonene is a popular additive in foods, cosmetics, cleaning products, and natural insect repellants. 
For example, it’s used in foods like sodas, desserts, and candies to provide a lemony flavor.

Limonene is extracted through hydrodistillation, a process in which fruit peels are soaked in water and heated until the volatile molecules are released via steam, condensed, and separated (4).

Due to its strong aroma, limonene is utilized as a botanical insecticide. 
It’s an active ingredient in multiple pesticide products, such as eco-friendly insect repellents (5).

Other household products containing this compound include soaps, shampoos, lotions, perfumes, laundry detergents, and air fresheners.

Additionally, limonene is available in concentrated supplements in capsule and liquid form. 
These are often marketed for their supposed health benefits.

This citrus compound is also used as an aromatic oil for its calming and therapeutic properties.

SUMMARY
Limonene is used in a range of products, including food, cosmetics, and eco-friendly pesticides. 
It can also be found in supplement form, as it may boost health and fight certain diseases.

Linked to several health benefits
Limonene has been studied for its potential anti-inflammatory, antioxidant, anticancer, and heart-disease-fighting properties.

However, most research has been conducted in test tubes or on animals, making it difficult to fully understand the role of limonene in human health and disease prevention.

Anti-inflammatory and antioxidant benefits
Limonene has been shown to reduce inflammation in some studies.

While short-term inflammation is your body’s natural response to stress and is beneficial, chronic inflammation can harm your body and is a major cause of illness. 
It’s important to prevent or reduce this type of inflammation as much as possible.

Limonene has been shown to reduce inflammatory markers that relate to osteoarthritis, a condition characterized by chronic inflammation.

A test-tube study in human cartilage cells noted that limonene reduced nitric oxide production. 
Nitric oxide is a signaling molecule that plays a key role in inflammatory pathways.

In a study in rats with ulcerative colitis — another disease characterized by inflammation — treatment with limonene significantly decreased inflammation and colon damage, as well as common inflammatory markers.

Limonene has demonstrated antioxidant effects as well. 
Antioxidants help reduce cell damage caused by unstable molecules called free radicals.

Free radical accumulation can lead to oxidative stress, which may trigger inflammation and disease.

One test-tube study revealed that limonene may inhibit free radicals in leukemia cells, suggesting a decrease in inflammation and cellular damage that would normally contribute to disease.

Although promising, these effects need to be confirmed by human studies.

May have anticancer effects
Limonene may have anticancer effects.

In a population study, those who consumed citrus fruit peel, the major source of dietary limonene, had a reduced risk of developing skin cancer compared to those who only consumed citrus fruits or their juices.


Additionally, research in rodents found that supplementing with limonene inhibited the growth of skin tumors by preventing inflammation and oxidative stress.

Other rodent studies indicate that limonene may fight other types of cancer, including breast cancer.

What’s more, when given to rats alongside the anticancer drug doxorubicin, limonene helped prevent several common side effects of the medication, including oxidative damage, inflammation, and kidney damage.

Although these results are promising, more human studies are needed.

May boost heart health
Heart disease remains the leading cause of death in the United States, accounting for nearly one in four deaths.

Limonene may lower your risk of heart disease by reducing certain risk factors, such as elevated cholesterol, blood sugar, and triglyceride levels.

In one study, mice given 0.27 grams of limonene per pound of body weight (0.6 grams/kg) showed reduced triglycerides, LDL (bad) cholesterol, fasting blood sugar, and fat accumulation in the liver, compared to a control group.

In another study, stroke-prone rats given 0.04 grams of limonene per pound of body weight (20 mg/kg) exhibited significant reductions in blood pressure compared to rats of similar health status that did not receive the supplement.

Keep in mind that human studies are needed before strong conclusions can be drawn.

Other benefits
Aside from the benefits listed above, limonene may:

Reduce appetite. The scent of limonene has been shown to significantly reduce appetite in blowflies. However, this effect has not been studied in humans.
Decrease stress and anxiety. Rodent studies suggest that limonene could be used in aromatherapy as an anti-stress and anti-anxiety agent.
Support healthy digestion. Limonene may protect against stomach ulcers. 
In a study in rats, citrus aurantium oil, which is 97% limonene, protected nearly all of the rodents against ulcers caused by medication use.
SUMMARY
Limonene may offer antioxidant, anti-inflammatory, anticancer, and anti-heart-disease benefits, among others. However, more research in humans is needed.

Safety and side effects
Limonene is considered safe for humans with little risk of side effects. 
The Food and Drug Administration (FDA) recognizes limonene as a safe food additive and flavoring (5).

However, when applied directly to the skin, limonene may cause irritation in some people, so caution should be used when handling its essential oil.

Limonene is sometimes taken as a concentrated supplement. 
Because of the way your body breaks it down, it’s likely safe consumed in this form. That said, human research on these supplements is lacking (26Trusted Source).

Notably, high-dose supplements may cause side effects in some people. 
What’s more, insufficient evidence exists to determine whether limonene supplements are acceptable for pregnant or breastfeeding women.

It’s best to consult your healthcare practitioner before taking limonene supplements, especially if you’re taking medications, are pregnant or breastfeeding, or have a medical condition.

SUMMARY
Aside from possible skin irritation associated with direct application, limonene is likely safe for most people to use and consume in moderation.

Potentially effective dosages
Because few limonene studies exist in humans, it’s difficult to provide a dosage recommendation.

Nonetheless, dosages of up to 2 grams daily have been safely used in studies (9Trusted Source, 14Trusted Source).

Capsule supplements that can be purchased online contain dosages of 250–1,000 mg. Limonene is also available in liquid form with typical dosages of 0.05 ml per serving.

However, supplements aren’t always necessary. You can easily obtain this compound by eating citrus fruits and peels.

For example, fresh orange, lime, or lemon zest can be used to add limonene to baked goods, drinks, and other items. 
What’s more, pulpy citrus juices, such as lemon or orange juice, boast limonene, too.

SUMMARY
While dosage recommendations don’t exist for limonene, 2 grams daily has been safely used in studies. 
In addition to supplements, you can obtain limonene from citrus fruits and zest.

The bottom line
Limonene is a compound extracted from the peels of citrus fruits.

Studies suggest that limonene may have anti-inflammatory, antioxidant, and anticancer effects. 
However, more research in humans is needed to confirm these benefits.

Try adding lemon, lime, or orange zest to your favorite dishes to boost your limonene intake.

Common uses of limonene
Limonene is a popular additive in foods, cosmetics, cleaning products, and natural insect repellants. 
For example, it’s used in foods like sodas, desserts, and candies to provide a lemony flavor.

Limonene is extracted through hydrodistillation, a process in which fruit peels are soaked in water and heated until the volatile molecules are released via steam, condensed, and separated (4).

Due to its strong aroma, limonene is utilized as a botanical insecticide. 
It’s an active ingredient in multiple pesticide products, such as eco-friendly insect repellents.

Other household products containing this compound include soaps, shampoos, lotions, perfumes, laundry detergents, and air fresheners.

Additionally, limonene is available in concentrated supplements in capsule and liquid form. These are often marketed for their supposed health benefits.

This citrus compound is also used as an aromatic oil for its calming and therapeutic properties.

SUMMARY
Limonene is used in a range of products, including food, cosmetics, and eco-friendly pesticides. 
It can also be found in supplement form, as it may boost health and fight certain diseases. 

Limonene, a colourless liquid abundant in the essential oils of pine and citrus trees and used as a lemonlike odorant in industrial and household products and as a chemical intermediate.

Limonene exists in two isomeric forms (compounds with the same molecular formula—in this case, C10H16—but with different structures), namely l-limonene, the isomer that rotates the plane of polarized light counterclockwise, and d-limonene, the isomer that causes rotation in the opposite direction. 
In the extraction of citrus juices d-limonene is obtained as a by-product, and it also occurs in caraway oil; l-limonene is present in pine needles and cones; dl-limonene, or dipentene, the mixture of equal amounts of the l- and d-isomers, is a component of turpentine.

Dipentene may be sulfurized to produce additives that improve the performance of lubricating oils under heavy loads; d-limonene is commercially converted to l-carvone, which has a caraway-seed flavour.

Limonene is a cyclic monoterpene that constitutes about 98% of the EOs in the peel, leaf, and flower of many citrus fruits, including oranges, mandarins, lemons, pummelos, grapefruits, and limes [26]. 
The concentration of Limonene varies between 32% and 98% depending on the variety, for example, in bergamot (32–45%), lemon (45–76%) and sweet orange (68–98%). 
In addition to citrus fruits, it is also abundantly found in edible plants such as neroli, thyme, rosemary, lavender, ginger, perilla, sage, cranberries, mint, cherries, lemongrass, lavenders, hemp, licorice, hops, mushrooms, celery, cardamom, and caraway [26, 27]. 

Limonene is widely used in foods, pharmaceuticals, beverages, and industrial solvents, owing to its flavor and aroma. 
It also possesses numerous therapeutic effects, including anti-inflammatory [28], antioxidant [29], antiviral [30], immunomodulatory [31, 32, 33], anti-nociceptive [34], anticancer [35], antidiabetic [36], analgesic [37], cardioprotective [38, 39], neuroprotective [40], hepatoprotective [29] and gastroprotective [41]

Limonene is useful commercially in environmentally-safe cleaning formulations, as a solvent, and as raw material in the synthesis of other chemicals, such as carvone.

This chemical is also useful as an insecticide and for assorted other purposes. 
Manufacturers separate limonene from the fruit’s peel by means of steam distillation, or a centrifugal process.


Limonene is one of the most common compounds found in the essential oils of aromatic plants. 
The occurrence of this monoterpene hydrocarbon in various plant genera could be attributed to its precursory role in the biosynthesis of other monoterpenes and its defensive role against herbivores. Due to the medicinal potential and application in the flavor and fragrance industries, limonene has been extensively investigated. In this paper the biosynthetic, ecological and pharmacological importance of limonene is presented in an attempt to coherently summarize some of the most salient aspects from various studies in a form of a concise review.

Limonene is an optically active compound, and exists in two enantiomeric forms: R and S. 
The R-(+)-enantiomer, also known as d-limonene, is the main compound in the essential oils of the peels of Citrus spp. and (+)-limonene is a cheap by-product of orange [5-7]. It is also abundant in some Lippia and Artemisia species [8,9]. The l-limonene is mainly found in the essential oils of Pinus (e.g. pine needle oils) and Mentha (e.g. spearmint) species 

What is limonene?
Limonene is a natural product found in the rinds of lemons and other citrus fruits, which explains the name. 
Limonene can be produced from these fruits through a process called steam distillation where steam is used to evaporate the limonene out of the rind. 
Once purified, it is a clear liquid with a sweet citrus smell. 
This citrus smell makes Limonene a popular fragrance in scented products of all varieties from lipsticks to bubble bath products.

Outside of cosmetic products, limonene also works as solvent in cleaning products that helps dissolve grease and as a natural insecticide for protecting plants from pests.

d-Limonene is a liquid with a pleasant lemon-like odor.
d-Limonene is used as a solvent to replace chlorinated hydrocarbons and other more volatile and toxic organic solvents. 
d-Limonene readily oxidizes when in contact with air. 
The oxidized form of d-limonene is a known skin sensitizer. 
A skin and eye irritant that may cause skin sensitization;
The racemic mixture of d-limonene and l-limonene is called limonene or dipentene (138-86-3). 
Estimated lethal dose orally for humans is 0.5 to 5 g/kg; 
Healthy men had diarrhea after an oral dose of 20 grams; 
Liver effects were noted in a chronic high-dose feeding study of mice; 
[AIHA] See "Limonene" and "l-Limonene."

Used in flavorings, fragrances, and cosmetics and as a solvent and wetting agent; 
Also used to make resins, insecticides, insect repellants, and animal repellants;

How does it work?
As limonene has a strong citrus smell, it can give that fragrance to products that would otherwise be unscented. 
Limonene can also be used to mask any ingredients that have a less pleasant smell. 
It is similarly used in some food and medicine to cover up unpleasant tastes.

As a solvent, Limonene is good at dissolving chemicals that don’t like dissolving in water. 
Oily and greasy substances repel water and can’t dissolve in it, but don’t repel limonene. 
While there is use for ingredients that dissolve oil in skin care products like cleansers and soaps, other ingredients are typically used.

 

Safety
What are the side effects?

Limonene is a known irritant to the skin and eyes and as such can trigger bad reactions like red, blistered, dry or cracked skin seen in contact dermatitis. 
It’s also possible to experience an allergic reaction to it.

As Limonene is usually only used for fragrance it may be worth looking for unscented products instead if you do experience any side effects mentioned above.

Interactions with other medicines:
There are no known interactions between limonene and medicines.

Antimicrobial activity: The antimicrobial properties of limonene, both as a pure compound and as one of the major components of the essential oils of several plant species, have been well investigated. Comparing the inhibitory effect of d-limonene and the essential oils from the fruits of orange, lemon, grapefruit and mandarin, Dabbah et al. [5] found pure limonene and the oil to be highly effective. At a concentration of 1000 µL/L, both the essential oil and limonene inhibited the growth of Salmonella 

Other names for limonene
(+)-(R)-4-isopropenyl-1-methylcyclohexene; (+)-limonene; (-)-limonene; (4R)-1-methyl-4-(1-methylethenyl)cyclohexene; (4S)-1-methyl-4-isopropenylcyclohex-1-ene; (D)-limonene; (R)-(+)-limonene; (R)-4-isopropenyl-1-methylcyclohexene; 1-methyl-4-(1-methylethenyl)cyclohexene; 4-mentha-1,8-diene; AISA 5203-L (+)limonene; cyclohexene, 1-methyl-4-(1-methylethenyl)-, (4R)-; d-limonene; dipentene; limonene; limonene, (+)-; limonene, (+-)-isomer; limonene, (R)-isomer; limonene, (S)-isomer


Limonene takes its name from French limon ("lemon"). Limonene is a chiral molecule, and biological sources produce one enantiomer: the principal industrial source, citrus fruit,
 contains D-limonene ((+)-limonene), which is the (R)-enantiomer. Racemic limonene is known as dipentene. D-Limonene is obtained commercially from citrus fruits through two
 primary methods: centrifugal separation or steam distillation.

D-Limonene is harsh terpene citrusy fruity orange berry tarty fresh light sweet strong peel oil commercial grade d-limonene may redistilled citrus terpenes will then carry orange-likeodor highly purified limon-ene.

Chemical reactions
Limonene is a relatively stable monoterpene and can be distilled without decomposition, although at elevated temperatures it cracks to form isoprene.[5] 
It oxidizes easily in moist air 
to produce carveol, carvone, and limonene oxide. With sulfur, it undergoes dehydrogenation to p-cymene.

Limonene occurs commonly as the D- or (R)-enantiomer, but racemizes to dipentene at 300 °C. 
When warmed with mineral acid, limonene isomerizes to the conjugated diene α-terpinene 
(which can also easily be converted to p-cymene). 
Evidence for this isomerization includes the formation of Diels–Alder adducts between α-terpinene adducts and maleic anhydride.

It is possible to effect reaction at one of the double bonds selectively. 
Anhydrous hydrogen chloride reacts preferentially at the disubstituted alkene, whereas epoxidation with mCPBA occurs at the trisubstituted alkene.

In another synthetic method Markovnikov addition of trifluoroacetic acid followed by hydrolysis of the acetate gives terpineol.

Biosynthesis
In nature, limonene is formed from geranyl pyrophosphate, via cyclization of a neryl carbocation or its equivalent as shown. 
The final step involves loss of a proton from the cation
 to form the alkene.

The most widely practiced conversion of limonene is to carvone. 
The three-step reaction begins with the regioselective addition of nitrosyl chloride across the trisubstituted double bond.
 This species is then converted to the oxime with a base, and the hydroxylamine is removed to give the ketone-containing carvone.

In plants
D-Limonene is a major component of the aromatic scents and resins characteristic of numerous coniferous and broadleaved trees: red and silver maple (Acer rubrum, Acer saccharinum), 
cottonwoods (Populus angustifolia), aspens (Populus grandidentata, Populus tremuloides) sumac (Rhus glabra), spruce (Picea spp.), various pines (e.g., Pinus echinata, Pinus ponderosa),
 Douglas fir (Pseudotsuga menziesii), larches (Larix spp.), true firs (Abies spp.), hemlocks (Tsuga spp.), cannabis (Cannabis sativa spp.), cedars (Cedrus spp.), various Cupressaceae,
 and juniper bush (Juniperus spp.). 

It contributes to the characteristic odor of orange peel, orange juice and other citrus fruits. 
To optimize recovery of valued components from citrus peel waste, d-limonene is typically removed.

Safety and research
D-Limonene applied to skin may cause irritation from contact dermatitis, but otherwise appears to be safe for human uses. 
Limonene is flammable as a liquid or vapor and it is toxic to aquatic life.

Uses
Limonene is common as a dietary supplement and as a fragrance ingredient for cosmetics products.
[As the main fragrance of citrus peels, D-limonene is used in food manufacturing and some medicines, such as a flavoring to mask the bitter taste of alkaloids, and as a fragrance in perfumery, aftershave lotions, bath products, and other personal care products.
D-Limonene is also used as a botanical insecticide. 
D-Limonene is used in the organic herbicide "Avenger".
It is added to cleaning products, such as hand cleansers to give a lemon or orange fragrance (see orange oil) and for its ability to dissolve oils. 
In contrast, L-limonene has a piny, turpentine-like odor.

D-Limonene is used as a solvent for cleaning purposes, such as adhesive remover, or the removal of oil from machine parts, as it is produced from a renewable source (citrus essential oil, 
as a byproduct of orange juice manufacture). 

It is used as a paint stripper and is also useful as a fragrant alternative to turpentine. 
Limonene is also used as a solvent in some model airplane glues and as a constituent in some paints. 
Commercial air fresheners, with air propellants, containing limonene are used by philatelists to remove self-adhesive postage stamps from envelope paper.

Limonene is also used as a solvent for fused filament fabrication based 3D printing. 
Printers can print the plastic of choice for the model, but erect supports and binders from HIPS, a polystyrene plastic that is easily soluble in limonene. 
As it is combustible, limonene has also been considered as a biofuel.

In preparing tissues for histology or histopathology, D-limonene is often used as a less toxic substitute for xylene when clearing dehydrated specimens. 
Clearing agents are liquids miscible with alcohols (such as ethanol or isopropanol) and with melted paraffin wax, in which specimens are embedded to facilitate cutting of thin sections for microscopy.

BUY D-LIMONENE FROM ATAMAN CHEMICALS
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The odour and uses of D-Limonene
Odour=> harsh terpene citrusy fruity orange berry tarty Fresh light and sweet citrusy odor with strong resemblance to Orange peel oil Commercial grade d-Limonene may be redistilled 'Citrus Terpenes' and will then carry more Orange-likeodor than a highly purified Limon-ene
Perfume-Uses=> Eau-de-colognes fresh-topnotes Citrus, Orange, Household-perfumes, Add-lift, Floral-types, Jasmin, Lavender, Pine, Woody-blends, As-Modifier, Lime, Grapefruit,
Orange, Corn, Spice, Chewing-gum,
Blends-well-with=> Citrus-notes, Gums,


Synonyms
d-Limonene : d-1-Methyl-4-isopropenyl-1-cyclohexene : d-p-Mentha-1,8(9)-diene : Limonene d pure 1-Methyl para iso propenyl-1-cyclohexene : d para Mentha-1,8-diene : d Limonene : Kautschin : Hesperidene : Citrene : Carvene : Cajeputene : PerfumersWorld
Contains=> *D-LIMONENE@100% :

Limonene, (+/-)- is a racemic mixture of limonene, a natural cyclic monoterpene and major component of the oil extracted from citrus rind with chemo-preventive and antitumor activities. 
The metabolites of DL-limonene, perillic acid, dihydroperillic acid, uroterpenol and limonene 1,2-diol are suggested to inhibit tumor growth through inhibition of p21-dependent signaling,
 induce apoptosis via the induction of the transforming growth factor beta-signaling pathway, inhibit post-translational modification of signal transduction proteins, result in G1 cell 
cycle arrest as well as cause differential expression of cell cycle- and apoptosis-related genes.

NCI Thesaurus (NCIt)
Polylimonene, also known as dipentene or cajeputene, belongs to the class of organic compounds known as menthane monoterpenoids. These are monoterpenoids with a structure based on the o-, m-, or p-menthane backbone. P-menthane consists of the cyclohexane ring with a methyl group and a (2-methyl)-propyl group at the 1 and 4 ring position, respectively. The o- and m- menthanes are much rarer, and presumably arise by alkyl migration of p-menthanes. Polylimonene exists as a solid and is considered to be practically insoluble (in water) and relatively neutral. Within the cell, polylimonene is primarily located in the membrane (predicted from logP) and cytoplasm. Polylimonene participates in a number of enzymatic reactions. In particular, polylimonene can be biosynthesized from p-menthane. Polylimonene can also be converted into limonene monoterpenoid and limonene-1, 2-diol. Polylimonene is a camphor, citrus, and herbal tasting compound that can be found in a number of food items such as dill, winter savory, summer savory, and cumin. This makes polylimonene a potential biomarker for the consumption of these food products.

Human Metabolome Database (HMDB)
Limonene is a monoterpene that is cyclohex-1-ene substituted by a methyl group at position 1 and a prop-1-en-2-yl group at position 4 respectively. 
It has a role as a human metabolite. It is a monoterpene and a cycloalkene. It derives from a hydride of a p-menthane.

D-Limonene
(+)-Limonene
5989-27-5
(R)-(+)-Limonene
(+)-carvene
(+)-(4R)-Limonene
(4R)-Limonene
D-(+)-Limonene
(R)-Limonene
(R)-p-Mentha-1,8-diene
Citrene
(+)-p-Mentha-1,8-diene
(R)-4-Isopropenyl-1-methyl-1-cyclohexene
D-Limonen
Carvene
Glidesafe
Glidsafe
Kautschiin
Refchole
(+)-R-Limonene
Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (4R)-
d-p-Mentha-1,8-diene
(D)-Limonene
Limonene, D-
(+)-4-Isopropenyl-1-methylcyclohexene
(+)-Dipentene
(4R)-4-isopropenyl-1-methylcyclohexene
(R)-(+)-p-Mentha-1,8-diene
Biogenic SE 374
(+)-alpha-Limonene
d-Limonene (natural)
d-Limoneno [Spanish]
Limonene, (+)-
(R)-1-Methyl-4-(1-methylethenyl)cyclohexene
(+)-(R)-Limonene
Hemo-sol
(4R)-(+)-Limonene
r-(+)-limonene
D-1,8-p-Menthadiene
NCI-C55572
EINECS 227-813-5
p-Mentha-1,8-diene, (R)-(+)-
(4R)-1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene
4betaH-p-mentha-1,8-diene
(+)-1,8-para-Menthadiene
AI3-15191
CHEBI:15382
1-Methyl-4-(1-methylethenyl)cyclohexene, (R)-
(R)-1-Methyl-4-(prop-1-en-2-yl)cyclohex-1-ene
(+) Limonene
Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (R)-
(4R)-1-methyl-4-isopropenylcyclohex-1-ene
(R)-(+)-4-Isopropenyl-1-methylcyclohexene
(4R)-1-methyl-4-(1-methylethenyl)cyclohexene
(+)-Limonene, stabilized with 0.03% tocopherol
Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (theta)-
(+)-Limonene, 96%, unstabilized
d-Limoneno
D-limonene [JAN]
(4R)-4-isopropenyl-1-methyl-cyclohexene
Citrus stripper oil
Terpenes and Terpenoids, limonene fraction
Sulfate turpentine, distilled
Dextro-limonene
d limonene
citre ne
65996-98-7
EINECS 266-034-5
D-(+)-Limonen
limonene, (R)-isomer
D-Limonene Reagent Grade
(4R)-1-methyl-4-prop-1-en-2-ylcyclohexene
PARA-MENTHA-1,8-DIENE
DTXSID1020778
(R)-(+)-Limonene, 95%
(R)-(+)-Limonene, 97%
(R)-(+)-Limonene, >=93%
Tox21_200400
(R)-(+)-Limonene, analytical standard
CAS-5989-27-5
(4R)-1-Methyl-4-(prop-1-en-2-yl)cyclohexene
(4R)-1-methyl-4-(1-methylvinyl)cyclohex-1-ene
(R)-(+)-Limonene, primary pharmaceutical reference standard
UNII-9MC3I34447 component XMGQYMWWDOXHJM-JTQLQIEISA-N
(R)-(+)-Limonene, purum, >=96.0% (sum of enantiomers, GC)
(R)-(+)-Limonene, technical, ~90% (sum of enantiomers, GC)
d-Limonene;D-LIMONENE;Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (4R)-;D-Limonene
(+)-(R)-4-isopropenyl-1-methylcyclohexene
(+)-limonene
(-)-limonene
(4R)-1-methyl-4-(1-methylethenyl)cyclohexene
(4S)-1-methyl-4-isopropenylcyclohex-1-ene
(D)-limonene
(R)-(+)-limonene
(R)-4-isopropenyl-1-methylcyclohexene
1-methyl-4-(1-methylethenyl)cyclohexene
4 Mentha 1,8 diene
4-mentha-1,8-diene
AISA 5203-L (+)limonene
cyclohexene, 1-methyl-4-(1-methylethenyl)-, (4R)-
d Limonene
d-limonene
dipentene
limonene
limonene, (+)-
limonene, (+-)-
limonene, (+-)-isomer
limonene, (R)-isomer
limonene, (S)-isomer


The inhibition ranged from 58% for grapefruit oil (on E. coli) to 99% for pure  d-limonene on the same microbe. 
The activity order in this assay was d-limonene>lemon oil>mandarin oil>orange oil>grapefruit oil.   
In subsequent studies, essential oils from the orange fruit had no activity against Gram-negative bacterial strains, while exhibiting appreciable activities against various fungal species [43]. 
These results were in agreement with the earlier report by Winniczuk and Parish, who observed that (low purity) d-limonene (66%) inhibited the growth of all yeasts and Gram-positive cocci, while lacking efficacy against Gram-negative bacterial strains. 
It was further observed that oxidized d-limonene derivatives, such as carveol, carvone and α-terpineol, when in solution with limonene, have higher antimicrobial activity than d-limonene  [45].    
A  recent  report has further shown that the essential oils of  Pimpinella flabellifolia (with 47% limonene) had higher activity against all test organisms with the exception of Klebsiella pneumoniae, for which it lacked efficacy [46].   
In a recent study by van Vuuren and Viljoen, the antimicrobial activity of the limonene enantiomers and the racemate singularly and in combination (1:1) with 1,8-cineole were investigated to establish possibly interaction. 
Using isobologram constructions it was shown that depending on the ratio and specific enantiomer, an additive, synergistic or antagonistic interaction may be observed between the various molecules.   


4.2. Antioxidant activity: Compounds with a basic isoprene structure possess antioxidant activity. 
Limonene is made up of two isoprene units, and the presence of two double bonds renders it a potential antioxidant compound. 
In an effort to validate this property, Keinan et al. found limonene to saturate easily the pulmonary membrane and thereby protect the lung cells from either exogenous or endogenous ozone, as well as other oxidant agents. 
Further reports have indicated that, the essential oil of celery, which contains 74.6% of limonene, exhibited high inhibitory activity towards malonaldehyde (MA) formation from squalene upon irradiation at the level of 500 μg/mL. 
At the same concentration the essential oil exhibited an appreciably high DPPH scavenging activity and also inhibited the oxidation  


Anti-inflammatory activity: The anti-inflammatory properties of limonene have been validated by various researchers. 
Souza et al. reported that the essential oils of Porophyllum ruderate and Conyza bonariensis inhibitethe lipopolysaccharide (LPS) induced inflammation and inflammatory cell migration in vivo. 
A similar effect was observed with pure limonene screened in the same assay. 
Inhalation of limonene by sensitized rats significantly prevented bronchial obstruction by reducing peribronchial inflammatory cell infiltration. 
Limonene is a low molecular lipophilic compound hence it can easily saturate cell membranes and thus provides an anti-inflammatory protection to the cells. 
The anti-inflammatory property  has  further  been  confirmed  using  a 5-lipoxygenase inhibition assay when a limonene  rich essential oil obtained from Helichrysum odoratissimum exhibited high 5-lipoxygenase inhibitory activity. 
Further analysis on pure enantiomers of limonene showed that (l)-(+)-limonene was approximately three-fold less active than the (S)-(–)-limonene enantiomer. 
The racemic mixture displayed an intermediate activity between the values of the two isomers tested separately. 
This observation is important because the pharmacological activity of essential oils can depend on a specific enantiomer and/or the ratio of enantiomers.

Anticancer activity: Plant derived natural products are highly sought after as potential chemotherapeutic and chemopreventive agents for carcinogenetic processes.  
Limonene has been well researched for its chemopreventive properties against several types of cancer. 
 
It also inhibits the development of ras oncogene-induced mammary carcinomas in rats. 
Limonene has further been reported to significantly reduce the development of azoxymethane-induced aberrant crypt foci in the colon of rats after administering 0.5% limonene in the drinking water. 
Like many other tested monoterpenes, limonene acts on tumor cells by blocking the G1-cell cycle, followed by apoptosis, redifferentiation and finally tumor regression in which tumor parenchyma is replaced by stroma elements [63,64]. 
A similar observation was also made by Ji et al. when d-limonene induced apoptosis in a dose- and time dependent manner in the K562 and HL60 cell lines

Insecticidal activity: Essential oils and their constituents have increasingly been considered to be an attractive alternative to harsh pesticides for the preservation of stored products. 
This is due to their apparent complex nature as they are a rich source of bioactive chemicals. 
Limonene is among many cyclic monoterpenes with known insecticidal properties. 
This follows numerous validation studies using different assays such as fumigation, contact and ingestion activities on insects. 
Using the dipping method, Haag [68] reported a 73% mortality of the water hyacinth weevil when dipped in the media with 50% of limonene. 
Further results on weevils were reported by Karr and Coats [69] when rice weevils (Sitophilus oryzae L.) were exposed to limonene mists. 
Through fumigation and exposure for 24 hours, limonene had an LC50 value of 19 ppm against rice weevils. 
However, this compound was found to have little or no effect on cockroaches using an ingestion assay.  
In subsequent studies, limonene was found to be lethal to both Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst). 

The lethality of this compound could be due to its ability to penetrate the insect body via the a) respiratory system (fumigation), b) the cuticle (contact effect), or c) digestive system (ingestion effect) [71]. 
Furthermore limonene at low concentrations had weak activity against Callosobruchus chinensis (L.) and Sitophilus oryzae (L.). 

The other important insecticidal effect of limonene is the inhibition of isoprenylation of protein in Plasmodium falciparum, which consequently arrests the development of the malarial parasites in the vector [73].   
Mites are a serious problem in many households. They are a source of allergens which leads to respiratory complications such as asthma [74,75]. 
The main control of mites had been the use of synthetic acaricides. 
However, with the increasing concern of risks on human health and other environmental problems, a call for replacing synthetic products with plant-derived acaricides has gained popularity. 
Henceforth there has been an increased search for natural acaricides, most of which have shown to be promising alternatives to synthetic compounds [76-78]. 

Plant essential oils in particular are known to possess acaricidal activity. 
This property is partly attributed to their lipophilic nature and high vapor pressure. 
Screening seven Citrus species alongside 49 other plants from other genera, Kim  et al. reported over 90% mortality of Dermanyssus gallinae  at  a  concentration  of 0.07 mg/cm2. 
The study on the toxicity effect of the oils on the test mites showed that only C. aurantifolia caused a mortality of over 90% at 0.07 mg/cm2, but other species were ineffective at this concentration. 
While other compounds in the oils may have contributed to the effect, limonene remains one of the major effective acaricidal compounds in the volatile oils of these species. 
Furthermore the essential oil of caraway (with 38.4% limonene and 58% carvone) and lemon grass (91.1% limonene) had LC50 values of 158.05 x 10-6 and 300.66 x 10-6 against mites following 24 hours exposure to the oils [79]. 

The activity was time dependent as incubation of the mites with the oils for 48 hours halved the LC50 values


Limonene as a potential allergen and toxic compound:  Toxicity of limonene has been investigated in various organisms. 

The most interesting studies however focused on the allergenic and toxicity properties of oxidized limonene in mammals. 
Investigating the volatile constituents of a fragrant plant Myoga, Wei et al.found (R)-(+)-limonene to be an important skin irritant in guinea-pigs. 
This observation was in agreement with the earlier reports by Klecak et al. and Okabe et al. 
Furthermore, Matura et al. [85] tested the allergenic effects of an oxidized mixture of limonene enantiomers in 2411 dermatitis patients. 
About 2.6% of patients reacted to one or both of the oxidized enantiomeric preparations. 
It was thus concluded that concomitant reactions to the fragrance mixture, colophonium,  Myroxylon pereirae and fragrance- related contact allergy were common in patients reacting to one or both of the oxidized limonene enantiomers. 
Limonene is one of the most often used fragrant terpenes and is prone to air oxidation. 
Henceforth the current European regulation on fragrances has added oxidized limonene to the test series for patients suspected to be susceptible to fragrance allergy [86]. 
The 7th Amendment to the European Cosmetic Directive on labeling stipulates that the presence of limonene and 25 other compounds needs to be stated in finished cosmetic products, if exceeding a threshold of 0.01% for rinse-off and 0.001% for leave-on products [87,88]  
5. Conclusions Limonene is an important natural compound with a wide range of uses. 

An impressive amount of work has been conducted on the biotransformation role in the production of other monoterpenes. 

The promising insecticidal activity of limonene provides a possible alternative natural insecticide for the control of pests in an attempt to prevent the spoilage of stored products [68,69,71]. 
The advantage of limonene over synthetic pesticides in this regard is its biodegradability, which makes it more environmentally friendly for both fumigation and contact applications. 
The broad range of pharmacological properties of limonene coupled with low toxicity offers the possibility of incorporating this compound into various medical and cosmetic formulations. 
Other pharmacological properties such as mild antimicrobial, antioxidant and anti-inflammatory activities accentuate its use as a flavoring compound in foodstuffs and beverages. 
Limonene has appreciably good chemopreventive activity which renders a great opportunity for further investigation. 

It is thus noteworthy stating that more interesting biological activities, biochemical modifications, as well as ecological findings, are likely to emanate from future research on this monoterpene hydrocarbon.

Ecological aspects of limonene   
Limonene has a broad ecological role in plants; it serves as an antifeedant as part of a defense mechanism, an antifungal and as an attractant for pollinators. 

A study on the Scotch pine trees, Pinus sylvestris L. both resistant and susceptible cultivars to the pine moth herbivore, Dioryctria zimmermani (Grote), showed that monoterpenes varied significantly when the plants were attacked. 
However, limonene was the only compound that was consistently higher in resistant cultivars. 

For many herbivores, limonene acts as an oviposition deterrent and is toxic to many herbivore species.  

A study on the volatile emissions pattern of different plant organs and pollen of Citrus limon revealed an intriguing variation in limonene emission regimes. 
This was done with respect to plant development patterns, which included young and adult leaves, buds, stamens, petals, pollen and pericarps of ripe and unripe fruits. 

In many samples, limonene was the main volatile compound detected in the gynaecium, epicarp and young leaves, where it reached levels of ca. 65%. 

As leaves matured, the limonene content reduced by half (30.1%), which could be related to the production of the defense metabolite limonene, by the more vulnerable young leaves [40]. 
The buds had 38.9% emission of limonene, which increased as the flowers opened to 44.3%. 
These variations could indicate an orientation cue for pollinators adopted by the flowers [40].   
Similar observations were reported in the late 80’s when Armbruster and co-workers [41] reported on an ecological relationship between Dalechampia magnoliifolia and D. spathula (Euphorbiaceae) with the pollinator, a male Euglossine bee. 

The flower’s morphology as well as the size of the pollinator (a male bee), together with the floral fragrances from various parts of the flowers were identified as important factors in the pollination biology. 
It was observed that the flowers, especially the pollen, were rich in limonene, which contributed substantially in attracting the pollinator.   

Limonene and other monoterpenes are thought to be important allelopathic agents in hot and dry climates. 
Because of their high vapor density, essential oils in general easily penetrate into soil adversely affecting the underground organisms, such as under growing plants. 

In their study, Scrivanti et al. [42] screened limonene and the essential oil of Tagetes minuta (which had 66.3% of limonene) for their allelopathic properties on Zea mays roots. 
Both limonene and the crude essential oil inhibited the growth of the roots of Z. mays seedlings. 
After 96 hours of exposure, limonene inhibited the root growth to 13.56 cm in length compared to the 15.09 cm of untreated roots. 
The essential oil of T. minuta inhibited the root’s growth to 6.21 cm in length compared to 15.09 cm of untreated ones. 

Clearly limonene, a major compound, alongside other monoterpenes in the essential oil of this plant, had a strong influence on the activity. 

This allelopathic property suggests that plants that exude limonene from their underground structures are able to slow down or even completely deter other plants from growing in their vicinity.  
4. The biological properties of limonene   

Limonene possesses significant chemopreventive and chemotherapeutic properties. 
This has been revealed through various research projects focusing on its medicinal potential. 

The broad use of limonene in soft drinks, cosmetics and many other flavoring products has raised interest in the antimicrobial, anticancer, toxicity, antiparasitic and many other properties of limonene. 
Conclusions of various reports on the pharmacological properties of limonene are summarised

Limonene as a starting material for synthesis of various natural products: 
The starting materials for synthesis of natural products has always posed a huge challenge as some of the chemical compounds used may either be toxic or potentially carcinogenic. 
For example a large scale synthesis of р-cymene has always involved the use of benzene with methyl and isopropyl halide in the presence of AlCl3 as a Lewis acid catalyst, or toluene with isopropyl alcohol. 
These reactions have low selectivity as both ortho and  para isomers are obtained and thus require further separation processes. 
The use of these chemical compounds are increasingly restricted by environmental legislation, hence the need for eco-friendly reagents for synthesizing р-cymene. 
Limonene has emerged to be one of the major successes in the quest for safe and non-toxic starting materials in the synthesis of this natural product. 

It has a six membered ring that can easily be aromatized, which makes it a suitable substitute for toxic aromatic intermediates, such as benzene and toluene. 
This follows a report by Martín-Luengo and co-workers [35] who used limonene as a starting material in the synthesis of р-cymene. 

The conversion was achieved under solvent free conditions over mesoporous silica-alumina supports heated by microwave irradiation. 

The conversion had high selectivity of 100% and also afforded high yields of the product within a short time interval. 

For example, 100% conversion of limonene to р-cymene was achieved with Siral 40 (silica gel designated content 40) after only 10 minutes. 

This demonstrates a fast and efficient conversion reaction that can be used in the production of р-cymene. 

The efficiency and high selectivity offers manufacturers a desirable alternative to the use of Friedel-Crafts alkylation of benzene or toluene for production of р-cymene.  

p-Cymene is an important aromatic compound used for synthesis of fine chemicals which are useful in the production of fragrances, flavoring compounds, herbicides, pharmaceuticals and p-cresol 


(4R)-1-Methyl-4-(1-methylethenyl) cyclohexene
(d)-Limonene
(R)-p-mentha-1,8-diene
(R)-p-mentha-1,8-diene
(R)-p-mentha-1,8-diene; d-limonene


(+)-limonén (sk)
(<I>R</I>)-p-menta-1,8-dien (hr)
(R)-1-metyl-4-(prop-1-én-2-yl)cyklohexén (sk)
(R)-p-menta-1,8-dieen (et)
(R)-p-menta-1,8-dieeni (fi)
(R)-p-menta-1,8-dien (no)
(R)-p-menta-1,8-dien (pl)
(R)-p-menta-1,8-dien (sl)
(R)-p-menta-1,8-dien (sv)
(R)-p-menta-1,8-diena (ro)
(R)-p-menta-1,8-dienas (lt)
(R)-p-menta-1,8-diene (it)
(R)-p-menta-1,8-dieno (es)
(R)-p-menta-1,8-dieno (pt)
(R)-p-menta-1,8-dién (hu)
(R)-p-mentadiēns-1,8 (lv)
(R)-p-mentha-1,8-dieen (nl)
(R)-p-mentha-1,8-dien (cs)
(R)-p-mentha-1,8-dien (da)
(R)-p-Mentha-1,8-dien (de)
(R)-p-mentha-1,8-diène;d-limonène; (fr)
(R)-p-μενθα-1,8-διένιο (el)
(R)-p-мeнта-1,8-диен (bg)
d-limoneen (et)
d-limonen (cs)
D-limonen (da)
d-Limonen (de)
d-limonen (hr)
d-limonen (no)
d-limonen (ro)
d-limonen (sl)
d-limonen (sv)
d-limonene (pl)
d-limonitas (lt)
d-limonén (hu)
d-limonēns (lv)
d-лимонен (bg)

CAS names
Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (4R)-
Other

IUPAC names
(+)-Limonene
(+)-Limonene; (+)-(4R)-Limonene; (+)-carvene ...
(+)-p-Mentha-1,8-dien
(4R)-(+)-1-methyl-4-prop-1-en-2-ylcyclohexene
(4R)-1-Methyl-4-(1-methylethenyl)cyclohexene
(4R)-1-methyl-4-(1-methylethenyl)cyclohexene
(4R)-1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene
(4R)-1-methyl-4-(prop-1-en-2-yl)cyclohexane
(4R)-1-methyl-4-(prop-1-en-2-yl)cyclohexene
(4R)-1-methyl-4-prop-1-en-2-ylcyclohexene
(4R)-4-Isopropenyl-1-methylcyclohexene
(4R)-isopropenyl-1-methylcyclohexene 
(R)-(+)-4-isopropenyl-1-methylcyclohexene
(R)-(+)-Limonen
(R)-(+)-para-mentha-1,8-diene
(R)-1-methyl-4-(1-methylethenyl)-cyclohexene
(R)-4-Isopropenyl-1-methyl-1-cyclohexene
(R)-4-Isopropenyl-1-methylcyclohexene
(R)-p-menta-1,8-dien
(R)-p-Mentha-1,8-dien
(R)-P-MENTHA-1,8-DIENE
(R)-P-mentha-1,8-diene
(R)-p-Mentha-1,8-diene
(R)-p-mentha-1,8-diene
(R)-p-mentha-1,8-diene
(R)-p-mentha-1,8-diene ; d-limonene
(S)-p-mentha-1,8-diene
1-methyl-4(prop-1-en-2-yl)-cyclonexene
1-Methyl-4-(1-methylethenyl)-cyclohexene
1-methyl-4-(1-methylethenyl)-Cyclohexene
1-methyl-4-(1-methylethenyl)-cyclohexene
1-methyl-4-([1R]-methylethenyl)-cyclohexene
1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene
1-Methyl-4-prop-1-en-2-ylcyclohexene
1-methyl-4-prop-1-en-2-ylcyclohexene
1-méthyl-4-prop-1-èn-2-yl-cyclohexène
4-Isopropenyl-1-methylcyclohexene 
4-isopropenyl-1-methylcyclohexene 
4-isopropenyl-1-methylcyclohexene 
4R)-1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene
BITTER ORANGE E.O.
CYCLOHEXEN,1-METHYL-4-(1-METHYLETHENYL)-,(R)
Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (4R)-
Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (R)-
Cyclohexene,1-methyl-4-(1-methylethenyl)-,(r)
D'-limonene
D-LIMONENE
D-Limonene
d-Limonene
d-limonene
D-LIMONENE
D-Limonene
D-limonene
d-Limonene
d-limonene
d-limonene (R)-p-mentha-1,8-diene
D-Limoneno
Limonene
limonene
Limonene
LIMONENE, D-
Limonene, D-
ORANGE OILORANGE BRAZIL OILCITRUS TERPENES
R)-p-mentha-1,8-diene
R)-p-mentha-1,8-diene, D-Limonene
r-p-mentha-1,8-dien

Trade names
Aceite d-Limoneno de Naranja
Citrus Terpenes
Citrusterpene
CLEARON M105
CLEARON P105
CLEARON P125
Cold Pressed Peel Oil
D'Limonene
D-Limonen
D-Limonene 
d-Limonene
D-LIMONENE BRAZIL
LIMONENE-D
NANOLET R1050-CH
ORANGE TERPENES
Orange Terpenes
Orange terpenes
Piccolyte C115
Piccolyte C125
Piccolyte C85
Piccolyte HM106 ULTR
Piccolyte S115
YS RESIN PX1150
YS RESIN TO-L
YS RESIN TO105
YS RESIN TO115
YS RESIN TO125
YS RESIN TR105

(d)-Limonene is widely used as a flavor and fragrance additive in consumer products, such as perfumes, beverages, detergents, and soaps. 
d-Limonene is further used as an ingredient in household cleaning products. 
In addition to its use in a variety of consumable products, limonene is used as a starting material for the synthesis of various natural products, such as p-cymene. 
The wide application of (d)-Limonene in industry and domestic amenities coupled to its vulnerability to ozone aided oxidation has raised research interest to investigate its various biochemical and pharmacological properties. 
Considering the volume of reports, its medicinal potential, wide cosmetic and other domestic uses, it is warranted to collate some of the research on this commercially important molecule


(4R)-1-Methyl-4-(1-methylethenyl) cyclohexene
(d)-Limonene
(R)-p-mentha-1,8-diene
(R)-p-mentha-1,8-diene
(R)-p-mentha-1,8-diene; d-limonene
(+)-limonén (sk)
(<I>R</I>)-p-menta-1,8-dien (hr)
(R)-1-metyl-4-(prop-1-én-2-yl)cyklohexén (sk)
(R)-p-menta-1,8-dieen (et)
(R)-p-menta-1,8-dieeni (fi)
(R)-p-menta-1,8-dien (no)
(R)-p-menta-1,8-dien (pl)
(R)-p-menta-1,8-dien (sl)
(R)-p-menta-1,8-dien (sv)
(R)-p-menta-1,8-diena (ro)
(R)-p-menta-1,8-dienas (lt)
(R)-p-menta-1,8-diene (it)
(R)-p-menta-1,8-dieno (es)
(R)-p-menta-1,8-dieno (pt)
(R)-p-menta-1,8-dién (hu)
(R)-p-mentadiēns-1,8 (lv)
(R)-p-mentha-1,8-dieen (nl)
(R)-p-mentha-1,8-dien (cs)
(R)-p-mentha-1,8-dien (da)
(R)-p-Mentha-1,8-dien (de)
(R)-p-mentha-1,8-diène;d-limonène; (fr)
(R)-p-μενθα-1,8-διένιο (el)
(R)-p-мeнта-1,8-диен (bg)

d-limoneen (et)
d-limonen (cs)
D-limonen (da)
d-Limonen (de)
d-limonen (hr)
d-limonen (no)
d-limonen (ro)
d-limonen (sl)
d-limonen (sv)
d-limonene (pl)
d-limonitas (lt)
d-limonén (hu)
d-limonēns (lv)
d-лимонен (bg)

CAS names
Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (4R)-
Other

IUPAC names
(+)-Limonene
(+)-Limonene; (+)-(4R)-Limonene; (+)-carvene ...
(+)-p-Mentha-1,8-dien
(4R)-(+)-1-methyl-4-prop-1-en-2-ylcyclohexene
(4R)-1-Methyl-4-(1-methylethenyl)cyclohexene
(4R)-1-methyl-4-(1-methylethenyl)cyclohexene
(4R)-1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene
(4R)-1-methyl-4-(prop-1-en-2-yl)cyclohexane
(4R)-1-methyl-4-(prop-1-en-2-yl)cyclohexene
(4R)-1-methyl-4-prop-1-en-2-ylcyclohexene
(4R)-4-Isopropenyl-1-methylcyclohexene
(4R)-isopropenyl-1-methylcyclohexene
(R)-(+)-4-isopropenyl-1-methylcyclohexene
(R)-(+)-Limonen
(R)-(+)-para-mentha-1,8-diene
(R)-1-methyl-4-(1-methylethenyl)-cyclohexene
(R)-4-Isopropenyl-1-methyl-1-cyclohexene
(R)-4-Isopropenyl-1-methylcyclohexene
(R)-p-menta-1,8-dien
(R)-p-Mentha-1,8-dien
(R)-P-MENTHA-1,8-DIENE
(R)-P-mentha-1,8-diene
(R)-p-Mentha-1,8-diene
(R)-p-mentha-1,8-diene
(R)-p-mentha-1,8-diene

(R)-p-mentha-1,8-diene ; d-limonene

(S)-p-mentha-1,8-diene

1-methyl-4(prop-1-en-2-yl)-cyclonexene

1-Methyl-4-(1-methylethenyl)-cyclohexene

1-methyl-4-(1-methylethenyl)-Cyclohexene

1-methyl-4-(1-methylethenyl)-cyclohexene

1-methyl-4-([1R]-methylethenyl)-cyclohexene

1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene

1-Methyl-4-prop-1-en-2-ylcyclohexene

1-methyl-4-prop-1-en-2-ylcyclohexene

1-méthyl-4-prop-1-èn-2-yl-cyclohexène

4-Isopropenyl-1-methylcyclohexene

4-isopropenyl-1-methylcyclohexene

4-isopropenyl-1-methylcyclohexene 

4R)-1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene
BITTER ORANGE E.O.
CYCLOHEXEN,1-METHYL-4-(1-METHYLETHENYL)-,(R)
Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (4R)-
Cyclohexene, 1-methyl-4-(1-methylethenyl)-, (R)-
Cyclohexene,1-methyl-4-(1-methylethenyl)-,(r)
D'-limonene
D-LIMONENE
D-Limonene
d-Limonene
d-limonene

D-LIMONENE

D-Limonene

D-limonene

d-Limonene

d-limonene

d-limonene (R)-p-mentha-1,8-diene

D-Limoneno
Limonene
limonene
Limonene
LIMONENE, D-
Limonene, D-
ORANGE OILORANGE BRAZIL OILCITRUS TERPENES
R)-p-mentha-1,8-diene
R)-p-mentha-1,8-diene, D-Limonene
r-p-mentha-1,8-dien

Trade names
Aceite d-Limoneno de Naranja
Citrus Terpenes
Citrusterpene
CLEARON M105
CLEARON P105
CLEARON P125
Cold Pressed Peel Oil
D'Limonene
D-Limonen
D-Limonene
d-Limonene
D-LIMONENE BRAZIL
LIMONENE-D

NANOLET R1050-CH
ORANGE TERPENES
Orange Terpenes
Orange terpenes
Piccolyte C115
Piccolyte C125
Piccolyte C85
Piccolyte HM106 ULTR
Piccolyte S115
YS RESIN PX1150
YS RESIN TO-L
YS RESIN TO105
YS RESIN TO115
YS RESIN TO125
YS RESIN TR105
Other names

Limonene is a colorless liquid aliphatic hydrocarbon classified as a cyclic monoterpene, and is the major component in the oil of citrus fruit peels.
The d-isomer, occurring more commonly in nature as the fragrance of oranges, is a flavoring agent in food manufacturing.
It is also used in chemical synthesis as a precursor to carvone and as a renewables-based solvent in cleaning products.
The less common l-isomer is found in mint oils and has a piny, turpentine-like odor.
The compound is one of the main volatile monoterpenes found in the resin of conifers, particularly in the Pinaceae, and of orange oil.

Limonene takes its name from French limon ("lemon"). 
Limonene is a chiral molecule, and biological sources produce one enantiomer: the principal industrial source, citrus fruit, contains d-limonene ((+)-limonene), which is the (R)-enantiomer.

 Racemic limonene is known as dipentene.
d-Limonene is obtained commercially from citrus fruits through two primary methods: centrifugal separation or steam distillation.


Preferred IUPAC name
1-Methyl-4-(prop-1-en-2-yl)cyclohex-1-ene
Other names
1-Methyl-4-(1-methylethenyl)cyclohexene
4-Isopropenyl-1-methylcyclohexene
p-Menth-1,8-diene
Racemic: dl-Limonene; Dipentene
Identifiers
CAS Number    
138-86-3 (R/S) check
5989-27-5 (R) check
5989-54-8 (S) check


Chemical reactions
Limonene is a relatively stable monoterpene and can be distilled without decomposition, although at elevated temperatures it cracks to form isoprene. 
It oxidizes easily in moist air to produce carveol, carvone, and limonene oxide.
With sulfur, it undergoes dehydrogenation to p-cymene.

Limonene occurs commonly as the d- or (R)-enantiomer, but racemizes to dipentene at 300 °C. 
When warmed with mineral acid, limonene isomerizes to the conjugated diene α-terpinene. 
Evidence for this isomerization includes the formation of Diels–Alder adducts between α-terpinene adducts and maleic anhydride.

It is possible to effect reaction at one of the double bonds selectively. 
Anhydrous hydrogen chloride reacts preferentially at the disubstituted alkene, whereas epoxidation with mCPBA occurs at the trisubstituted alkene.

In another synthetic method Markovnikov addition of trifluoroacetic acid followed by hydrolysis of the acetate gives terpineol.

Biosynthesis
In nature, limonene is formed from geranyl pyrophosphate, via cyclization of a neryl carbocation or its equivalent as shown.
The final step involves loss of a proton from the cation to form the alkene.


he most widely practiced conversion of limonene is to carvone. 
The three-step reaction begins with the regioselective addition of nitrosyl chloride across the trisubstituted double bond. 
This species is then converted to the oxime with a base, and the hydroxylamine is removed to give the ketone-containing carvone.

In plants
d-Limonene is a major component of the aromatic scents and resins characteristic of numerous coniferous and broadleaved trees: 
red and silver maple (Acer rubrum, Acer saccharinum), cottonwoods (Populus angustifolia), aspens (Populus grandidentata, Populus tremuloides) sumac (Rhus glabra), spruce (Picea spp.), various pines (e.g., Pinus echinata, Pinus ponderosa), Douglas fir (Pseudotsuga menziesii), larches (Larix spp.), true firs (Abies spp.), hemlocks (Tsuga spp.), cannabis (Cannabis sativa spp.),[9] cedars (Cedrus spp.), various Cupressaceae, and juniper bush (Juniperus spp.).

It contributes to the characteristic odor of orange peel, orange juice and other citrus fruits.
To optimize recovery of valued components from citrus peel waste, d-limonene is typically removed.


Limonene is flammable as a liquid or vapor and it is toxic to aquatic life.

Uses
Limonene is common as a dietary supplement and as a fragrance ingredient for cosmetics products.
As the main fragrance of citrus peels, d-limonene is used in food manufacturing and some medicines, such as a flavoring to mask the bitter taste of alkaloids, and as a fragrance in perfumery, aftershave lotions, bath products, and other personal care products.
d-Limonene is also used as a botanical insecticide.
d-Limonene is used in the organic herbicide "Avenger". 
It is added to cleaning products, such as hand cleansers to give a lemon or orange fragrance (see orange oil) and for its ability to dissolve oils.
In contrast, l-limonene has a piny, turpentine-like odor.

Limonene is used as a solvent for cleaning purposes, such as adhesive remover, or the removal of oil from machine parts, as it is produced from a renewable source (citrus essential oil, as a byproduct of orange juice manufacture).[11] 
It is used as a paint stripper and is also useful as a fragrant alternative to turpentine. 
Limonene is also used as a solvent in some model airplane glues and as a constituent in some paints. 
Commercial air fresheners, with air propellants, containing limonene are used by philatelists to remove self-adhesive postage stamps from envelope paper.

Limonene is also used as a solvent for fused filament fabrication based 3D printing.
Printers can print the plastic of choice for the model, but erect supports and binders from HIPS, a polystyrene plastic that is easily soluble in limonene. 
As it is combustible, limonene has also been considered as a biofuel.

In preparing tissues for histology or histopathology, d-limonene is often used as a less toxic substitute for xylene when clearing dehydrated specimens. 
Clearing agents are liquids miscible with alcohols (such as ethanol or isopropanol) and with melted paraffin wax, in which specimens are embedded to facilitate cutting of thin sections for microscopy

Nomenclature
Chem. Abstr. Serv. Reg. No.: 5989-27-5
Chem. Abstr. Name: (R)-1-Methyl-4-(1-methylethenyl)cyclohexene
IUPAC Systematic Name: (R)-(+)-para-Mentha-1,8-diene
Synonyms: (+)-Dipentene; (R)-4-isopropenyl-1-methyl-1-cyclohexene; D-limonene;
d-(+)-limonene; D-(+)-limonene; (+)-limonene; (+)-α-limonene; (+)-(R)-limonene;
(+)-(4R)-limonene; (R)-limonene; (R)-(+)-limonene; (4R)-(+)-limonene; (+)-paramentha-1,8-diene; (R)-p-mentha-1,8-diene; (R)-(+)-para-mentha-1,8-diene


d-Limonene has been used for many years as a flavour and fragrance additive in foods, beverages and consumer products. 
It is increasingly used as a solvent. 
It is also used in the manufacture of resins, as a wetting and dispersing agent and in insect control (National Toxicology Program, 1991; IARC, 1993; Budavari, 1996).


1.3 Occurrence
1.3.1 Natural occurrence
d-Limonene is one of the most common terpenes in nature, occurring in citrus and a wide variety of other plant species. 
It is a major constituent of oil of citrus rind, dill oil,oil of cumin, neroli, bergamot and caraway 

1.3.2 Occupational exposure
According to the 1981–83 National Occupational Exposure Survey (National Institute for Occupational Safety and Health, 1998), approximately 138 300 workers in the United States were potentially exposed to d-limonene. 
Occupational exposure to d-limonene may occur during its production and use, notably as an industrial solvent.

1.3.3 Environmental occurrence
The average daily dietary intake of d-limonene has been estimated to be about 0.3 mg/kg bw (Flavor and Extract Manufacturers’ Association, 1991).

d-Limonene has been detected in indoor and outdoor air in various locations (IARC,1993; National Library of Medicine, 1998).


Limonene could produce an antistress action by altering ortho/parasympathetic parameters as well as central neurotransmitter functions.

d-Limonene has been produced since 1995 and has been used as a flavor and fragrance additive in cleaning and cosmetic products, food, beverages, and pharmaceuticals. 
It is also increasingly used as a solvent. 
It is used in the manufacturing of resins, as a wetting and dispersing agent, and in insect control. 
It is present in most of the essential oils commonly used in Australia, particularly citrus oils. 
In the workplace, products such as hand cleaners, industrial cleaners, degreasers, and strippers may also contain limonene as a solvent. 
Industrial limonene is produced by alkaline extraction of citrus residues and steam distillation. This distillate contains more than 90% d-limonene.

Limonene is used as a substitute for chlorinated hydrocarbons, chlorofluorocarbons, and other solvents. 
It is used in degreasing metals (30% limonene) prior to industrial painting, for cleaning in the electronics industry (50–100% limonene), for cleaning in the printing industry (30–100% limonene), and in paint as a solvent. 
Limonene is also used as a solvent in histology laboratories and as a flavor and fragrance additive in food, household cleaning products, and perfumes. 
d-Limonene has been used as a gallstone solubilizer in humans.

d-Limonene has also been used as a sorption promoter or accelerant for improving transdermal drug delivery and works by penetrating the skin to reversibly decrease barrier resistance. 
Commercial mixtures of d-limonene molecules may contain other forms of limonene (l-limonene and d,l-limonene), which are called terpenes, and related compounds such as p-cumene.

Some studies have indicated that limonene has anticancer effects. 
Limonene increase the levels of liver enzymes involved in detoxifying carcinogens. 
The glutathione-S-transferase (GST) system eliminates carcinogens. 
The GST system can be promoted by limonene in the liver and small bowel leading to a decrease in the damaging effects of carcinogens. 
Animal studies demonstrated that dietary limonene reduced mammary tumor growth.


Limonene is a mild skin and eye irritant. Ingestion of 20 g of d-limonene caused diarrhea and a temporary increase in protein in the urine (proteinurea) in five male volunteers. 
These data, in addition to the low acute toxicity in animal tests, suggest that d-limonene is not very toxic by ingestion.

Air levels of d-limonene may irritate the eyes and airways of some people, especially when the levels build up indoor

d-Limonene has been used successfully for the postoperative dissolution of retained cholesterol gallstones.

Limonene, and possibly linoleic and oleic acids, can have irritative and bronchconstrictive airway effects and can cause reduced vital capacity. 
Patients with significant inhalational exposure should be removed from the environment and undergo appropriate decontamination. 
Inhaled β2-adrenoceptor agonists can be used for bronchoconstriction.

Urinary tract
Limonene ingested in sufficient quantity can cause proteinuria. 
However, nephropathy and renal tumors are not expected in humans.

Skin
Contact dermatitis has been attributed to limonene, and a purpuric rash has been attributed to topical exposure to d-limonene.

Autoxidation of d-limonene readily occurs, yielding a variety of oxygenated monocyclic terpenes that are strong contact allergens. 
The prevalence of contact allergy after exposure to d-limonene among patients with dermatitis has been studied. 

The proportion of positive patch tests to oxidized d-limonene was comparable to that seen with several allergens in the standard series, and patients who reacted to d-limonene often reacted to fragrance mix, balsam of Peru, and colophony.

Limonene (p-Mentha-1,8-diene) (Fig. 27.2) is a monoterpene found in the oils of Citrus plants like lemon, mandarin, orange, grapefruit, and bergamot. 
This 10-carbon cyclohexanoid monoterpene has two enantiomers: R and S. R enantiomer is the main enantiomer in the essential oils of limonene. 
Limonene can be converted to various alcohols, acids, and ketones by some microorganisms and plants.


Polarity of limonene is too low. 
Therefore it blocks the passage of limonene through cell membranes and leads to less activity.

Limonene can be completely absorbed in humans and other mammalian species. 
It can be rapidly distributed in most of the tissues and quickly metabolized into various active metabolites. 
Limonene and/or its active metabolites can be found in serum, liver, lung, kidney, and many tissues. 
This important monoterpene can accumulate in adipose tissue and mammary glands.


Limonene is a colourless liquid at room temperature. 
The structural formula for limonene is given below.
The chemical exists as two optical isomers, d- and l-limonene, and the racemic mixture dipentene. 
The purity of commercial d-limonene is about 90–98%. 


d-Limonene 
l-Limonene 
Dipentene

CAS no. 5989-27-5 
5989-54-8 
138-86-3

Chemical name 
(R)-1-methyl-4-(1-methylethenyl) cyclohexene
(S)-1-methyl-4-(1-methylethenyl) cyclohexene
1-methyl-4-(1-methylethenyl)cyclohexene

Empirical formula 
C10H16 
C10H16 
C10H16

Molecular weight 
136.23 
136.23 
136.23

Melting point (°C) 
!74.35 
!74.35 
!95.9

Boiling point (°C) 
175.5–176.0 
175.5–176.0 
175.5–176.0

Density (g/cm3 at 20°C) 
0.8411 
0.8422 
0.8402

Vapour pressure (Pa at 20°C) 
190 
190 
190

Water solubility (mg/litre at 25°C) 13.8b – –

Henry’s law constant (kPa m3/molat 25°C)34.8c – –

Log Kow 4.23d – 4.83e(limonene)
 

d-Limonene is a long-term solution for the industry.

It is around us every day. 
It”s in food products such as chewing gum, citrus juices, vegetables, herbs, and is also used as a flavor additive in drinks.

It”s used in air fresheners, soaps and perfumes.

It is also being used in various medical procedures, and is demonstrating success as a chemotherapeutic agent in human clinical trials.

d-Limonene has made news recently in research reports, indicating the successful treatment of asthma.

It has been used to treat chronic bronchitis and acute sinusitis.

It has even been used to treat children with acute and chronic sinus infections.

In addition to all of these uses, it is still the “green” solvent of choice in the industrial and institutional cleaning products arena.

Sounds like a safe chemical of choice for textile care.

d-Limonene has many other positive attributes:

It is not carcinogenic or mutagenic.
It is biodegradable and contains no ozone depleting chemicals.
It is generally recognized as safe (GRAS) by the Food and Drug Administration (FDA) and thereby is approved for use in food contact applications.
It is also approved for us as an inert ingredient by the Environmental Protection Agency (EPA).

d-Limonene has many other positive attributes:

It is not carcinogenic or mutagenic.
It is biodegradable and contains no ozone depleting chemicals.
It is generally recognized as safe (GRAS) by the Food and Drug Administration (FDA) and thereby is approved for use in food contact applications.
It is also approved for us as an inert ingredient by the Environmental Protection Agency (EPA).

D-limonene is a monoterpene obtained from a variety of citrus fruit peel oil which is the most important residue in citrus industry. 
It is food grade and presents antioxidant properties. 
The use of antioxidants additives in polymers for food packaging is a common practice to reduce their potential thermo-oxidative degradation during processing and they could also prevent the food oxidation reducing the direct addition of antioxidants to the food. 
Among them, the great interest towards the use of renewable natural resources in the food packaging industry makes natural antioxidants candidates to stabilize biodegradable polymer formulations. 
In this sense, poly(lactic acid) (PLA) seems to be the most attractive biodegradable polymer for food packaging industry. 
Thus, the aim of this work was to study the thermal degradation of PLA films stabilized with D-limonene. 
Kinetic parameters were obtained by thermogravimetric analysis (TGA) in dynamic mode and the apparent activation energies (Ea) were calculated by the Friedman method. 
The comparison of Ea between PLA stabilized with D-limonene and non-stabilized polymer furnished information on the thermal stabilization performance. 
The results indicate that D-limonene shows good performance in the PLA stabilization and therefore the possibility of its use as additive intended for food packaging materials.


This chemical is a clear, colorless liquid. 
It is a primary ingredient in citrus oils and can be found naturally in citrus fruits. 
As such, it emits a strong, pleasant odor and has a similar taste. 
According to the FDA, d-limonene is generally regarded as safe (GRAS) for human consumption. 
One primary application of d-limonene is as a flavoring agent. 
It can be found in a variety of food items, including sodas, juices, and ice cream. 
This substance has also been found to neutralize gastric problems, including acid reflux and heartburn. 
It can also help dissolve cholesterol in the body, so it is used as a treatment for that as well. 
In concentrated doses, d-limonene can be slightly toxic and may irritate the skin or eyes.
It produces sharp vapors that could hurt the lungs, so a breathing mask should be worn. 
It may also evaporate in the air, so it should be stored in an airtight container.


 

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