Essential oils contain large amounts of terpenoids, but the terpenoids are the individual compounds in the mixture.
Terpenes are hydrocarbons formed from several isoprene units.
Terpenoids can be thought of as modified terpenes.
Examples are geraniol, pinene, and menthol.
Biologically, terpenoids are classed as lipids. They are found in all classes of living things.
Essential oils are concentrated, pleasant-smelling, volatile liquids obtained from plants, usually by solvent extraction or by steam distillation.
They are "essential" in the sense that they contain the "essence" of the plant's fragrance.
Terpenoids are the main constituent of essential oils and contribute to their scent.
About 500 essential oils amounting to 120 000 t are produced commercially. Here are the constituents of some of them.
- Sweet orange oil — mainly limonene.
- Mentha arvensis (wild mint) — menthol, menthone, isomenthone, neomenthol, limonene, piperitone, β-caryophyllene, α-pinene, β-pinene, methyl acetate, tannins, and flavonoids.
- Peppermint oil — menthol, menthone, menthyl acetate, menthofuran, 1,8-cineol, limonene, pulegone, caryophyllene, and pinene.
- Cedarwood oil — α-cedrene, β-cedrene, thujopsene, cedrol, and widdrol.
- Lemon oil — α-pinene, camphene, β-pinene, sabinene, myrcene, α-terpinene, linalool, β-bisabolene, limonene, trans-α-bergamotene, nerol, and neral.