A REVIEW ON TERPENOIDS: SOURCES, ISOLATION AND CHARACTERISTICS OF MENTHOL AND CITRAL

Abstract

Terpenoids represent a vast and chemically diverse class of natural products formed from isoprene building blocks, extensively distributed throughout plants, where they predominantly occur in essential oils. They play an important role in pharmacognosy due to their aromatic properties and significant pharmacological activities such as antimicrobial, anti-inflammatory, carminative, and analgesic effects. Menthol and citral are important monoterpenoid constituents commonly used in pharmaceutical, cosmetic, and food industries. Menthol is obtained mainly from Mentha piperita and related Mentha species, while citral is isolated from Cymbopogon citratus (lemongrass) and Cymbopogon flexuosus. Isolation of menthol is generally carried out by steam distillation of peppermint oil followed by cooling and crystallization, whereas citral is isolated by steam distillation and fractionation of lemongrass oil.