Terpenes and terpenoids are the primary constituents of the essential oils of many types of plants and flowers. These compounds belong to the isoprenoid group. Even though isoprene itself has not been found in nature, its polymers, terpenic hydrocarbons and their oxygen derivatives are very often present in large quantities in different plant species. The resin produced by most plants is a viscous liquid, composed mainly of volatile fluid terpene3. The single isoprene unit, therefore, represents the most basic class of terpenes, the hemiterpenes. An isoprene unit bound to a second isoprene is the defining characteristic of terpene, which is also a monoterpene (C10). Sesquiterpenes contain three isoprene units (C15), while diterpenes
(C20) and triterpenes (C30) contain two and three terpene units respectively. Tetraterpenes consist of four terpene units, polyterpenes more than four such units. In nature, terpenes occur predominantly in the form of hydrocarbons, alcohols and their glycosides, ethers, aldehydes, ketones, carboxylic acids and esters. Apart from broad structural diversity, terpenes also exhibit a wide array of biological actions. Essential oils have antimicrobial, antiparasitic, insecticidal and antioxidant/prooxidant activities that often represent the combined bioactivity of multiple components10. Many plant terpenoids are cytotoxic towards tumour cells and are applied as chemotherapeutic or chemo-preventive compounds1,2. Terpenes play an important role as signal compounds and growth regulators (phytohormones) of plants10. Many insects metabolize the terpenes which they may have obtained from their plant food for synthesizing growth hormones and pheromones10. Many plant and insect resins like Lac resin also have economically beneficial properties, useful for varnishes and adhesives4.
This protocol describes a rapid, small-scale, high-throughput assay for approximating the total terpenoids content in plant tissue using a monoterpene, Linalool as standard reagent with conc. sulfuric acid. In this reaction Geraniol (primary alcohol, C10H18O) may be produced from Linalool (Tertiary alcohol, C10H18O). Alpha-terpineol (C10H18O) or such monocyclic terpenoids may further be produced from geraniole3. It is very obscured to explain the exact chemical nature of the reaction in where a brick red precipitation has been formed and which is partially soluble in reaction mixture solution and chloroform but fully in methanol. All estimation has been done spectroscopically at 538 nm.