Terpenes

Terpenes are secondary metabolites formed by multiplication (polymerization) of a five carbon unit (the isoprene). They are structurally diversified due to the variable numbers of conjugated double bonds and cyclisation level of their scaffolds. The smallest (slighest) molecules containing from 5 to 15 carbons are volatile and contribute to attractive fragrances and cooling effects. They are represented by isoprene (C5), monoterpenes (C10) and sesquiterpenes (C15). The twenty carbons (C20) terpenes (diterpenes) forms plant resins and glues. C30 terpenes (triterpenes) are characterized by high structural variability due to different glycosylation and oxygenation patterns (by hydroxyl, carboxyl, epoxyl). C40 unit terpenes (tetraterpenes) play key roles in yellow-orange pigmentation in plant world (e.g. carotenoids, xanthophylls). All the terpene families show chemotaxonomical values through exclusive occurrence or differential regulations in different plant taxa.