α-Pinene is an organic compound of the terpene class, one of two isomers of pinene.[1] It is an alkene and it contains a reactive four-membered ring. It is found in the oils of many species of many coniferous trees, notably the pine. It is also found in the essential oil of rosemary (Rosmarinus officinalis).[2] Both enantiomers are known in nature; (1S,5S)- or (−)-α-pinene is more common in European pines, whereas the (1R,5R)- or (+)-α-isomer is more common in North America. The racemic mixture is present in some oils such as eucalyptus oil.

a-pinene is a natural essential oil with special chemial activity, is the material of synthetic camphor, compound essence, synthetic resin, pharmaceutical and other organic synthesis industries.In the atmosphere alpha-pinene undergoes reactions with ozone, the OH radical or the NO3 radical,[6] leading to low-volatility species which partly condense on existing aerosols, thereby generating secondary organic aerosols

SabineneSabinene is a natural bicyclic monoterpene with the molecular formula C10H16. It is isolated from the essential oils of a variety of plants including holm oak (Quercus ilex) and Norway spruce (Picea abies). It has a strained ring system with cyclopentane ring fused to a cyclopropane ring.

Sabinene is one of the chemical compounds that contributes to the spiciness of black pepper and is a major constituent of carrot seed oil. It also occurs in tea tree oil at a low concentration. It is also present in the essential oil obtained from nutmeg.[2]

MyrceneMyrcene, or β-myrcene, is an olefinic natural organic compound. It is classified as a hydrocarbon, more precisely as a monoterpene. Terpenes are dimers of isoprene, and myrcene is one of the most important. It is a component of the essential oil of several plants including bay, ylang-ylang, wild thyme, and hops.[3][4] It is produced mainly semi-synthetically from myrcia, from which it gets its name. It is a key intermediate in the production of several fragrances. α-Myrcene is the name for the structural isomer 2-methyl-6-methylene-1,7-octadiene, which is not found in nature and is little used.[5]

Use in fragrance industry

Myrcene is an important intermediate used in the perfumery industry. It has pleasant odor, but is rarely used directly. It is also unstable in air, tending to polymerize. Samples are stabilized by the addition of alkylphenols or tocopherol. It is thus more highly valued as an intermediate for the preparation of flavor and fragrance chemicals such as menthol, citral,

citronellol, citronellal, geraniol, nerol, and linalool. Treatment of myrcene with hydrogen chloride gives geranyl chloride, neryl chloride, and linalyl chloride. Treatment of these compounds with acetate gives geranyl acetate, neryl acetate, and linalyl acetate, respectively. These esters are then hydrolyzed to the corresponding alcohols. Myrcene is also converted to myrcenol, another fragrance found in lavender, via uncatalyzed hydroamination of the 1,3-diene followed by hydrolysis and Pd-catalyzed removal of the amine.

As 1,3-dienes, both myrcene and mycenol undergo Diels-Alder reactions with several dienophiles such as acrolein to give cyclohexene derivatives that are also useful fragrances.[2][edit]Partial list of the plants that contain myrcene

As mentioned above, many plants contain myrcene, sometimes in very large amounts.[5]HouttuyniaMangoesHopsLemon grassWest Indian Bay TreeVerbenaMercia

LimoneneLimonene is a colourless liquid hydrocarbon classified as a cyclic terpene. The more common D isomer possesses a strong smell of oranges.[1] It is used in chemical synthesis as a precursor to carvone and as a renewably-based solvent in cleaning products.

Limonene takes its name from the lemon, as the rind of the lemon, like other citrus fruits, contains considerable amounts of this compound, which contributes to their odor. 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 (CAS number 5989-27-5, EINECS number 227-813-5). Racemic limonene is known as dipentene.[2] D-Limonene is obtained commercially from citrus fruits through two primary methods: centrifugal separation or steam distillation.

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 base, and the hydroxylamine is removed to give the ketone-containing carvone.[1]

Limonene is common in cosmetic products. As the main odor constituent of citrus (plant family Rutaceae), D-limonene is used in food manufacturing and some medicines, e.g. as a flavoring to mask the bitter taste of alkaloids, and as a fragrant in perfumery; it is also used as botanical insecticide.,[6] particularly the (R)-(+)-enantiomer is most active as an insecticide. It is added to cleaning products such as hand cleansers to give a lemon-orange fragrance (see orange oil). In contrast, L-limonene has a piney, turpentine-like odor.

In natural and alternative medicine, D-limonene is marketed to relieve gastroesophageal reflux disease and heartburn.[7]

Limonene is increasingly being used as a solvent for cleaning purposes, such as the removal of oil from machine parts, as it is produced from a renewable source (citrus oil, as a byproduct of orange juice manufacture). It also serves as a paint stripper when applied to painted wood and is also useful as a fragrant alternative to turpentine. Limonene is also used as a solvent in some model airplane glues. All-natural commercial air fresheners, with air propellants, containing limonene are used by philatelists to remove self-adhesive postage stamps from envelope paper.[8]

As it is combustible, limonene has also been considered as a biofuel.[9]

Limonene can be used to dissolve polystyrene, and is a more ecologically friendly substitute for acetone.[citation needed]

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

Safety

Limonene and its oxidation products are skin and respiratory irritants, and limonene-1,2-oxide (formed by aerial oxidation) is a known skin sensitizer. Most reported cases of irritation have involved long-term industrial exposure to the pure compound, e.g. during degreasing or the preparation of paints. However a study of patients presenting dermatitis showed that 3% were sensitized to limonene.[13]

Although high doses have been shown to cause renal cancer in male rats,[14] limonene is considered by some researchers to be a potential chemopreventive agent [15] with value as a dietary anti-cancer tool in humans.[16] There is no evidence for carcinogenicity or genotoxicity in

humans. The IARC classifies D-limonene as a Group 3 carcinogen: not classifiable as to its carcinogenicity to humans.[13][17]

No information is available on the health effects of inhalation exposure to D-limonene in humans,[dubious – discuss] and no long-term inhalation studies have been conducted in laboratory animals.[citation needed]

D-Limonene is biodegradable, but due to its low flash point, it must be treated as hazardous waste for disposal.[citation needed]

LinaloolLinalool ( /lɪˈnælɵ.ɒl/) is a naturally occurring terpene alcohol chemical found in many flowers and spice plants with many commercial applications, the majority of which are based on its pleasant scent (floral, with a touch of spiciness). It has other names such as β-linalool, linalyl alcohol, linaloyl oxide, p-linalool, allo-ocimenol, and 2,6-dimethyl-2,7-octadien-6-ol.

Over 200 species of plants produce linalool, mainly from the families Lamiaceae (mints, scented herbs), Lauraceae (laurels, cinnamon, rosewood), and Rutaceae (citrus fruits), but also birch trees and other plants, from tropical to boreal climate zones. It has also been found in some fungi.

Linalool is used as a scent in 60–80% of perfumed hygiene products and cleaning agents including soaps, detergents, shampoos, and lotions.[1] It is also used as a chemical intermediate. One common downstream product of linalool is Vitamin E. In addition, linalool is used by pest professionals as a flea and cockroach insecticide.

Linalool is used in some mosquito repellent products, however the EPA notes that: "A preliminary screen of labels for products containing Linalool (as the sole active ingredient) indicates that efficacy data on file with the Agency may not support certain claims to repel mosquitos."[2]

Akio Nakamura together with colleagues from the University of Tokyo and T. Hasegawa Co., Ltd in Kawasaki, Japan, claim to have demonstrated that inhaling linalool can reduce stress in lab rats. In a study published in The

Journal of Agriculture and Food Chemistry,[3] they exposed the animals to stressful conditions and found that those inhaling linalool saw their stress-elevated levels of neutrophils and lymphocytes fall to near-normal levels compared with the controls. Inhaling linalool also reduced the activity of more than 100 genes that "go into overdrive" in stressful situations. The findings could form the basis of new blood tests for identifying fragrances that can soothe stress, the researchers claim.[4]

Linalool gradually breaks down when in contact with oxygen, forming an oxidized by-product that may cause allergic reactions such as eczema in susceptible individuals. Between 5–7% of patients undergoing patch testing in Sweden were found to be allergic to the oxidized form of linalool.[1] Ways to minimize exposure include not buying large bottles of perfumed hygiene products, and replacing the lid after each use.

CitronellalCitronellal or rhodinal or 3,7-dimethyloct-6-en-1-al (C10H18O) is a monoterpenoid, the main component in the mixture of terpenoid chemical compounds that give citronella oil its distinctive lemon scent.

Citronellal is a major isolate in distilled oils from the plants Cymbopogon,[2] lemon-scented gum, and lemon-scented teatree.

Citronellal has insect repellent properties, and research shows high repellent effectiveness against mosquitoes.[3] Research shows that citronellal has strong antifungal qualities.[4]

CitralCitral, or 3,7-dimethyl-2,6-octadienal or lemonal, is either of, or a mixture of, a pair of terpenoids with the molecular formula C10H16O. The two compounds are double bond isomers. The E-isomer is known as geranial or citral A. The Z-isomer is known as neral or citral B.Citral is present in the oils of several plants, including lemon myrtle (90-98%), Litsea citrata (90%), Litsea cubeba (70-85%), lemongrass (65-85%), lemon tea-tree (70-80%), Ocimum gratissimum (66.5%), Lindera citriodora (about 65%), Calypranthes parriculata (about 62%), petitgrain (36%), lemon verbena (30-35%), lemon ironbark (26%), lemon balm (11%), lime (6-9%), lemon (2-5%), and orange.[2][3][4]

Geranial has a strong lemon odor. Neral's lemon odor is less intense, but sweeter. Citral is therefore an aroma compound used in perfumery for its

citrus effect. Citral is also used as a flavor and for fortifying lemon oil. It also has strong antimicrobial qualities,[5] and pheromonal effects in insects.[6][7]

Citral is used in the synthesis of vitamin A, ionone, and methylionone, and to mask the smell of smoke.

CampheneCamphene is bicyclic monoterpene. It is nearly insoluble in water, but very soluble in common organic solvents. It volatilizes readily at room temperature and has a pungent smell. It is a minor constituent of many essential oils such as turpentine, cypress oil, camphor oil, citronella oil, neroli, ginger oil, and valerian. It is produced industrially by catalytic isomerization of the more common alpha-pinene. Camphene is used in the preparation of fragrances and as a food additive for flavoring. Its mid-19th century use as a fuel for lamps was limited by its explosiveness.

Eucalyptol is a natural organic compound which is a colorless liquid. It is a cyclic ether and a monoterpenoid.

Eucalyptol is also known by a variety of synonyms: 1,8-cineol, 1,8-cineole, limonene oxide, cajeputol, 1,8-epoxy-p-menthane, 1,8-oxido-p-menthane, eucalyptol, eucalyptole, 1,3,3-trimethyl-2-oxabicyclo[2,2,2]octane, cineol, cineole.

In 1870, F.S. Cloez identified and ascribed the name eucalyptol to the dominant portion of Eucalyptus globulus oil.[1] Eucalyptus oil, the generic collective name for oils from the Eucalyptus genus, should not be confused with the chemical compound eucalyptol.

Eucalyptol comprises up to 90 percent of the essential oil of some species of the generic product Eucalyptus oil,[1] hence the common name of the compound. It is also found in camphor laurel, bay leaves, tea tree, mugwort, sweet basil, wormwood, rosemary, sage and other aromatic plant foliage. Eucalyptol with a purity from 99.6 to 99.8 percent can be obtained in large quantities by fractional distillation of eucalyptus oil.

Although it can be used internally as a flavoring and medicine ingredient at very low doses, typical of many essential oils (volatile oils), eucalyptol is toxic if ingested at higher than normal doses.[2]

Uses[edit]Flavoring and fragrance

Because of its pleasant spicy aroma and taste, eucalyptol is used in flavorings, fragrances, and cosmetics. Cineole based eucalyptus oil is used as a flavouring at low levels (0.002%) in various products, including baked goods, confectionery, meat products and beverages.[3] In a 1994 report released by five top cigarette companies, eucalyptol was listed as one of the 599 additives to cigarettes. It is claimed that it is added to improve the flavor.[edit]Medicinal Eucalyptol suppository, for the treatment of some respiratory ailments

Eucalyptol is an ingredient in many brands of mouthwash and cough suppressant.

Primary Research:In a 2003 study eucalyptol was found to control airway mucus hypersecretion and asthma, after in a previous study the authors found eucalyptol to suppress arachidonic acid metabolism and cytokine production in human monocytes.[4][5]In a 2004 study it was found to inhibit cytokine production in cultured human lymphocytes and monocytes.[6]In a 2004 study Eucalyptol was found to be an effective treatment for nonpurulent rhinosinusitis. Treated subjects experienced less headache on bending, frontal headache, sensitivity of pressure points of trigeminal nerve, impairment of general condition, nasal obstruction, and rhinological secretion. Side effects from treatment were minimal.[7]A 2000 study found Eucalyptol to reduce inflammation and pain when applied topically.[8]In a 2002 study it was found to kill leukaemia cells of two cultured human leukemia cell lines, but not cells of a human stomach cancer cell line in vitro.[9][edit]Insecticide and repellent

Eucalyptol is used as an insecticide and insect repellent.[10][11]

Conversely, eucalyptol is one of many compounds that is attractive to males of various species of orchid bees, who apparently gather the chemical to synthesize pheromones; it is commonly used as bait to attract and collect these bees for study.[12]

The terpinenes are a group of isomeric hydrocarbons that are classified as terpenes. They each have the same molecular formula and carbon framework, but they differ in the position of carbon-carbon double bonds. α-Terpinene has been isolated from cardamom and marjoram oils, and from other natural sources. β-Terpinene has no known natural source, but has been prepared synthetically from sabinene. γ-Terpinene and δ-terpinene (also known as terpinolene) are natural and have been isolated from a variety of plant sources

CariophylleneCaryophyllene ( /ˌkæri.ɵfɪˈliːn/), or (−)-β-caryophyllene, is a natural bicyclic sesquiterpene that is a constituent of many essential oils, especially clove oil, the oil from the stems and flowers of Syzygium aromaticum (cloves),[1] the essential oil of hemp Cannabis sativa,[2] rosemary Rosmarinus oficinalis,[3] and hops.[4] It is usually found as a mixture with isocaryophyllene (the cis double bond isomer) and α-humulene (obsolete name: α-caryophyllene), a ring-opened isomer. Caryophyllene is notable for having a cyclobutane ring, a rarity in nature.

Caryophyllene is one of the chemical compounds that contributes to the spiciness of black pepper. In a study conducted by Jürg Gertsch et al. from the Swiss Federal Institute of Technology (ETH Zurich), beta-caryophyllene was shown to selectively bind to the cannabinoid receptor type-2 (CB2) and to exert significant cannabimimetic antiinflammatory effects in mice.[2] Since the widespread plant natural product beta-caryophyllene is an FDA approved food additive and ingested daily with food it is the first dietary cannabinoid. Whether this compound is able to modulate inflammatory processes in humans via the endocannabinoid system is yet unknown. Beta-caryophyllene does not bind to the centrally expressed cannabinoid receptor type-1 (CB1) and therefore does not exert psychomimetic effects.

The first total synthesis of caryophyllene in 1964 by E.J. Corey was considered one of the classic demonstrations of the possibilities of synthetic organic chemistry at the time.[5]