Geranyl acetate is the acetate ester of geraniol, a key acyclic monoterpenoid widely present in essential oils. It is characterized by its sweet fruity-rose aroma, making it a valuable compound in perfumery and flavoring applications. In addition to its sensory properties, geranyl acetate exhibits mild antimicrobial activity, primarily attributed to its ability to modulate membrane fluidity in microbial cells.
Chemical Properties
Geranyl acetate ((E)-3,7-dimethylocta-2,6-dien-1-yl acetate; C₁₂H₂₀O₂; molecular weight 196.29 g/mol) is a colorless to pale yellow liquid. It presents a boiling point of 138°C at 15 mmHg, a density of 0.907 g/cm³, and a refractive index (nD20) ranging from 1.457 to 1.462. Structurally, it contains a primary acetate group and a transoid C2=C3 double bond configuration. The compound undergoes enzymatic hydrolysis via esterases to yield geraniol and acetic acid, and can isomerize under acidic conditions to form linalyl acetate. With a logP of approximately 4.2, it is insoluble in water but readily miscible in ethanol and most organic solvents.
Biosynthetic Pathway
Geranyl acetate is biosynthesized via the methylerythritol phosphate (MEP) pathway in plastids. Geranyl diphosphate is first converted into geraniol through the action of a phosphatase, followed by acetylation into geranyl acetate mediated by alcohol acyltransferases (AATs) of the BAHD enzyme family, using acetyl-CoA as the acetyl donor. This compound is found in high concentrations in essential oils such as palmarosa (Cymbopogon martinii, 70–85%), rose otto (Rosa damascena, 5–15%), and geranium (Pelargonium graveolens, 3–10%). Additionally, engineered microbial systems, including recombinant Escherichia coli expressing geraniol acetyltransferases, have demonstrated production yields ranging from 200 to 500 mg/L.
