ABSTRACT
Triterpenoids are a large group of naturally occurring substances of relatively complex cyclic structures with a carbon skeleton based on six isoprene units. Their immediate biological precursor is the acyclic C30 hydrocarbon, squalene (Figure 20.1). Because of multiple substitutions of functional groups they may occur either as alcohols, aldehydes, or carboxylic acids and their appropriate esters, ethers, or glycosides. This makes that multiple triterpenoid structures can be identified in many plant families and also in animal tissues. In general, they can be divided into at least four major classes: true triterpenes,1 steroids,2 saponins,3,4 and cardiac glycosides.5
