In
addition, pairwise condensation of FDP and GGDP gives rise
to the classes of triterpenoids (C30) and tetraterpenoids (C40),
respectively, and assembly of an undefined number of C5
precursors yields polyterpenoids. In addition to the regular
terpenoids (Cn · 5), a large number of irregular terpenoids
and terpenoid derivatives (e.g. homoterpenes) as well as
terpenoid conjugates (e.g. monoterpene indole alkaloids;
Facchini and DeLuca, 2008) are formed in plants.