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Linalool
IUPAC name	3,7-dimethylocta-1,6-dien-3-ol
Identifiers
CAS number	78-70-6 Y
PubChem	6549
SMILES	CC(O)(C=C)CCC=C(C)C
InChI	1/C10H18O/c1-5-10 (4,11)8-6-7-9(2)3/h5, 7,11H,1,6,8H2,2-4H3
Properties
Molecular formula	C10H18O
Molar mass	154.25 g/mol
Density	0.858 – 0.868 g/cm3
Melting point	< 20 °C
Boiling point	198 – 199 °C
Solubility in water	1.589 g/l
Hazards
Flash point	55 °C
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Linalool (pronounced /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.

In nature

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.

Enantiomers

Linalool has a stereogenic center at C₃ and therefore two stereoisomers: licareol is (R)-(–)-linalool with CAS No. 126–90–9 (PubChem 67179) and coriandrol is (S)-(+)-linalool with CAS No. 126–91–0 (PubChem 13562).

(S)-(+)-linalool (left) and (R)-(–)-linalool (right)

Both enantiomeric forms are found in nature: S-linalool is found, for example, as a major constituent of the essential oils of coriander (Coriandrum sativum L. family Apiaceae) seed, palmarosa [Cymbopogon martinii var martinii (Roxb.) Wats., family Poaceae], and sweet orange (Citrus sinensis Osbeck, family Rutaceae) flowers. (R)-linalool is present in lavender (Lavandula officinalis Chaix, family Lamiaceae), laurel (Laurus nobilis, family Lauraceae), and sweet basil (Ocimum basilicum, family Lamiaceae), among others.

Each enantiomer evokes different neural responses in humans, and therefore are classified as possessing distinct scents. 3S-(+)-linalool is perceived as sweet, floral, petitgrain-like (odor threshold 7.4 ppb) and the 3R-form as more woody and lavender-like (odor threshold 0.8 ppb)

Biosynthesis

In higher plants linalool as other monoterpenoids is produced from isopentenyl pyrophosphate via the universal isoprenoid intermediate geranyl pyrophosphate, through a class of membrane-bound enzymes named monoterpene synthases. One of these, linalool synthase (LIS), has been reported to produce (S)-linalool in several floral tissues.

Uses

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. Additionally, linalool is used by pest professionals as a flea and cockroach insecticide. Akio Nakamura and colleagues at T. Hasegawa Co., Ltd in Kawasaki, Japan, claim to have demonstrated that inhaling linalool can reduce stress, in lab rats at least. 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.

List of the plants that contain the chemical

• Cinnamomum tamala ^[2]
• Ocimum basilicum ^[3]

Safety information

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.

Compendial status

Notes & References

Notes

1. ^ ^{a b} Widely Used Fragrance Ingredients In Shampoos And Conditioners Are Frequent Causes Of Eczema
2. ^ Ahmed, Aftab et al. (2000). "Essential oil constituents of the spice Cinnamomum tamala (Ham.) Nees & Eberm". Flavour and Fragrance Journal 15 (6): 388–390. doi:10.1002/1099-1026(200011/12)15:6<388::AID-FFJ928>3.0.CO;2-F.  
3. ^ Klimánková, Eva et al. (2008). "Aroma profiles of five basil (Ocimum basilicum L.) cultivars grown under conventional and organic conditions". Food Chemistry 107 (1): 464–472. doi:10.1016/j.foodchem.2007.07.062.  

General references

• Casabianca H, Graff JB, Faugier V, Fleig F, Grenier C (1997) Enantiomeric distribution studies of linalool and linalyl acetate. A powerful tool for authenticity control of essential oils. HRC J High Res Chrom 21:107-112

• Lewinshon E, Schalechet F, Wilkinson J, Matsui K, Tadmor Y, Nam K, Amar O, Lastochkin E, Larkov O, Ravid U, Hiatt W, Gepstein S, Pichersky E (2001) Enhanced levels of the aroma and flavor compound S-linalool by metabolic engineering of the terpenoid pathway in tomato fruits. Plant Physiol 127:1256–1265

• Pengelly, Andrew. The Constituents of Medicinal Plants. 2nd Ed. 2004. CABI Publishing, U.S.A. and UK.

• Raguso RA, Pichersky E (1999) A day in the life of a linalool molecule: chemical communication in a plant-pollinator system. Part 1: linalool biosynthesis in flowering plants. Plant Species Biol 14:95-120

• Akio Nakamura, Satoshi Fujiwara, Ichiro Matsumoto and Keiko Abe. Stress Repression in Restrained Rats by (R)-(−)-Linalool Inhalation and Gene Expression Profiling of Their Whole Blood Cells. J. Agric. Food Chem., 2009, 57 (12), pp 5480–5485.

See also

• Lavender
• Zanthoxylum simulans

External links

• Comprehensive data sheet
• Record in the Household Products Database of NLM