Chemical Diversity of Terpenoids
Several thousand terpenes and terpenoids occur in many genera of higher plants and organisms [11,
12] and although often the structures of the various classes seem unrelated, detailed biochemical
studies have revealed their biosynthesis patterns [13]. The terpenes are biosynthetically constructed
from isoprene (2-methylbutadiene) units [10,14]. The C5H8 isoprenes polymerise and subsequently fix
the number and position of the double bonds. The basic molecular formulae of terpenes are thus
multiples of C5H8. Most terpenes have cyclic structures and are classified by the number of C5 isoprene
units that they contain. Given the many ways the basic C5 units can be combined, it is not surprising to
observe the amount and diversity of the structures [15]. The classes are: hemiterpenes consisting of a
single C5 isoprene unit, monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), sesterterpenes