Ocimene is an acyclic monoterpene widely emitted by plants, playing key roles in pollinator attraction, herbivore defense, and industrial fragrance applications.

Chemical Structure and Isomers

Ocimene (C₁₀H₁₆, MW 136.23) exists as α-, β-, and γ-isomers, with β-ocimene (3,7-dimethylocta-1,3,6-triene) featuring three double bonds in an eight-carbon chain substituted with methyl groups at positions 3 and 7. The trans-β form predominates, with InChIKey IHPKGUQCSIINRJ-CSKARUKUSA-N and a characteristic sweet, herbaceous scent.

Its conjugated diene system confers high volatility and reactivity, enabling efficient UV detection in GC-MS analyses.

Natural Sources and Emission

Ocimene occurs in a wide range of plant species, including basil, mint, lavender, hops, orchids, parsley, and mangoes, contributing significantly to floral and herbaceous scent profiles. It is released from leaves and flowers either constitutively or in response to herbivore attack.

Its biosynthesis follows the methylerythritol phosphate (MEP) pathway, where terpene synthases catalyze the conversion of geranyl pyrophosphate (GPP) into ocimene. Emission levels typically peak during flowering stages or under biotic and abiotic stress conditions.