Plant Terpenes

Terpenoids are hydrocarbon natural products based on five-carbon (isoprene) units as their building blocks, numbering more than 30,000 molecules having been discovered to-date. These compounds are classified as to the number of isoprene units, which include the hemiterpenes (1), monoterpenes (2), sesquiterpenes (3), diterpenes (4), sesterterpenes (5), triterpenes (6) and polyterpenes (many units). Of these different major classes of terpenoids, the diterpenes are structurally most diversified, possessing at least 6 large structural groups, within which are more than 20 sub-structural types. The triterpenes are the second largest class, containing two major structural groups and more than 15 sub-structural types. Biologically active compounds are found in each class of the terpenoids, particularly among the sesquiterpenes, diterpenes and triterpenes. In this chapter, chemical descriptions, examples, biosynthetic origin of the various major classes, structural types and sub-types are presented. As far as possible, biological activities of the example of each type or sub-types of terpenes terpenoids are presented. Due to the vast number of different types and sub types, the discussions presented in this chapter, are by necessity, brief. However, the present treatment is meant to stimulate further chemical and biological research, particularly with drug discovery and development being a focal point.