Page 129 - Pharmd general phytochemistry I-Final2024_LEUCTERS

Classification of terpenoids
 The classification of terpenoids depends on the number of isoprene units incorporated

into a particular compound; these can be summarized as follows:

Monoterpenoid two isoprene units (C10H16)
Sesquiterpenoids three isoprene units (C15H24)
Diterpenoids four isoprene units (C20H32)
Sesterpenes five isoprene units (C25H40)
Triterpenoids six isoprene units (C30H48)
Tetraterpenoids eight isoprene units (C40H64)
(carotenoids)

Sesquiterpene Lactones

 They are C-15 lactone derivatives derived from farnesyl pyrophosphate. The latter is a

condensation product of three isoprene units.
 Generally, they can be classified according to their carbocyclic skeletons into

germacranolides, guaianolides, eudesmanolides, xanthanolides and others.

O O O

Germacranolide O Guaianolide

Some carbocyclic skeletons of sesquiterpene lactones
 A structural feature of most of these compounds which appears to be associated with

much of the biological activities is the α,β-unsaturated-γ-Iactone with an exocyclic
methylene function.

α, β-unsaturated-γ-lactone with exocyclic methylene

127