Following cyclization, further diversity is conferred by modification of the products by oxidation,
hydroxylation, glycosylation and other substitutions mediated by cytochrome P450-dependent
monooxygenases, glycosyl transferases and other enzymes. Little is known about the enzymes required
for these chemical elaborations. One common feature shared by all saponins is the presence of a sugar
chain attached to the aglycone. Glycosylation is particularly important as the sugar chain is critical for
the biological activity of many saponins [27,28]. The oligosaccharide chains are likely to be
synthesized by sequential addition of single sugar residues to the aglycone, but little is known about
triterpenoid glycosylation