Linalool
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Linalool (Template:IPAc-en) refers to two enantiomers of a naturally occurring terpene alcohol found in many flowers and spice plants.<ref name="pubchem">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Together with geraniol, nerol, citronellol, linalool is one of the rose alcohols.<ref name=KO/> Linalool has multiple commercial applications, the majority of which are based on its pleasant scent (floral, with a touch of spiciness).<ref name="Ullmann">Template:Ullmann</ref><ref>Template:Cite journal</ref>
A colorless oil, linalool is classified as an acyclic monoterpenoid.<ref name=pubchem/> In plants, it is a metabolite, a volatile oil component, an antimicrobial agent, and an aroma compound.<ref name=pubchem/> Linalool has uses in manufacturing of soaps, fragrances, food additives as flavors, household products, and insecticides.<ref name=pubchem/> Esters of linalool are referred to as linalyl, e.g. linalyl pyrophosphate, an isomer of geranyl pyrophosphate.<ref name=Crot>Template:Cite journal</ref>
The word linalool is based on linaloe (a type of wood) and the suffix Template:Linktext.<ref>Template:Merriam-Webster: "International Scientific Vocabulary, from Mexican Spanish lináloe"</ref> In food manufacturing, it may be called coriandrol.<ref name=pubchem/>
OccurrenceEdit
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.), cymbopogon (Cymbopogon martini var. martinii), and sweet orange (Citrus sinensis) flowers. (R)-linalool is present in lavender (Lavandula officinalis), bay laurel (Laurus nobilis), and sweet basil (Ocimum basilicum), among others.
Each enantiomer evokes distinct neural responses in humans, so each is classified as possessing distinct scents. (S)-(+)-Linalool is perceived as sweet, floral, petitgrain-like (odor threshold 7.4 ppb) and the (R)-form as more woody and lavender-like (odor threshold 0.8 ppb).
Over 200 species of plants produce linalool, notably from the families Lamiaceae (mint and other herbs), Lauraceae (laurels, cinnamon, rosewood), and Rutaceae (citrus fruits), but also birch trees and other plants, from tropical to boreal climate zones.
- Aniba rosaeodora
- Lavandula<ref>Template:Cite journal</ref>
- Cinnamomum tamala<ref name=eocs>Template:Cite journal</ref>
- Cannabis sativa<ref name="Ibrahim">Template:Cite journal</ref>
- Basil<ref name=apfb>Template:Cite journal</ref>
- Solidago (goldenrod)<ref>Template:Cite journal</ref>
- Artemisia vulgaris (mugwort)
- Humulus lupulus (hop)
It was first synthesized in the laboratory of Leopold Ružička in 1919.<ref name=em90>Albert Eschenmoser: "Leopold Ruzicka - From the Isoprene Rule to the Question of Life's Origin" CHIMIA 44 (1990)</ref>
ProductionEdit
Linalool is produced commercially from several terpenes and terpenoid precursors, which are often components of terpentine. 2-Pinanol, derived from pinene, gives linalool upon pyrolysis.<ref>Template:Ullmann</ref>
BiosynthesisEdit
In higher plants linalool is formed by rearrangement of geranyl pyrophosphate (GPP).<ref name="Planta Medica">Template:Cite journal</ref> With the aid of linalool synthase (LIS), water attacks to form the chiral center.<ref>Template:Cite book</ref><ref name="Planta Medica"/> LIS appears to show a limonene synthase-type catalysis through a simplified "metal-cofactor-binding domain [where the majority] of the residues involved in substrate...binding [are] in the C-terminal part of the protein" suggesting stereoselectivity and the reasoning behind why some plants have varying levels of each enantiomer.<ref name="Molecular Biology and Evolution">Template:Cite journal</ref><ref name="Plant Physiol">Template:Cite journal</ref>
Odor and flavorEdit
Linalool has complex odor and flavor properties. Its odor is similar to floral, spicy wood, somewhat resembling French lavender plants, bergamot oil or lily of the valley.<ref name=pubchem/> It has a light, citrus-like flavor, sweet with a spicy tropical accent.<ref name=pubchem/> Linalool is used as a scent in perfumed hygiene products and cleaning agents, including soaps, detergents, shampoos, and lotions.<ref name=pubchem/><ref name="Ullmann"/> It exhibits antimicrobial and antifungal properties.<ref name=pubchem/><ref>Template:Cite journal</ref>
Chemical derivativesEdit
Linalool is hydrogenated to give dihydro- and tetrahydrolinalool, which are fragrances that are more resilient toward oxidants, as might be found in household cleaning products. Linalyl acetate, a popular scent, is produced by esterification of linalool (as well as occurring naturally). Isomerization of linalool gives geraniol and nerol.<ref name=KO>Template:Cite book</ref>
SafetyEdit
Linalool can be absorbed by inhalation of its aerosol and by oral intake or skin absorption, potentially causing irritation, pain and allergic reactions.<ref name="Ullmann" /><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Some 7% of people undergoing patch testing in Europe were found to be allergic to the oxidized form of linalool.<ref>Template:Cite journal</ref>
The US Food and Drug Administration (FDA) lists linalool in the Code of Federal Regulations under substances generally recognized as safe, synthetic flavoring substances and adjuvants.<ref name="21CFR182.60">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>