Citronellol is a saturated acyclic monoterpenoid alcohol widely used in rose-based fragrances and recognized for its biological activities, including neuroprotective, antimicrobial, and anticancer effects. These properties are primarily associated with its ability to modulate reactive oxygen species (ROS) and induce regulated cell death mechanisms such as necroptosis.

Chemical Properties

Citronellol (3,7-dimethyloct-6-en-1-ol; C₁₀H₂₀O; molecular weight 156.27 g/mol) is a colorless, viscous liquid characterized by a boiling point of 220–222°C, a density of 0.857 g/cm³, and a refractive index (nD20) of 1.458. The molecule contains a chiral center at carbon C3, giving rise to two enantiomers: (R)-(+)-citronellol, typically associated with rose-geranium notes, and (S)-(-)-citronellol, which exhibits a more lemon-like odor profile. Its primary alcohol functional group enables diverse chemical transformations, including esterification to form acetates and benzoates, oxidation to citronellal or citronellic acid, and hydrogenation reactions. With a logP value of 4.0, citronellol displays low aqueous solubility (approximately 0.13 g/L), reflecting its hydrophobic character.

Biosynthetic Pathway

Citronellol is biosynthesized from geranyl diphosphate (GPP) through NADPH-dependent reduction of citronellal, catalyzed by geraniol/citronellol dehydrogenases. This pathway is naturally active in plant species such as Cymbopogon (citronella grass, containing 35–50% citronellol), as well as in rose and geranium essential oils. In addition to plant-based production, microbial biosynthesis strategies have been developed using engineered Escherichia coli strains expressing citronellal reductase (CR; EC 1.1.1.185), achieving production titers in the range of 300–800 mg/L in glucose-fed fermentation systems.