Structures and biosynthesis of the main diterpenes found in S. pomifera leaves. a The names of the isolated compounds from S. pomifera leaves are: (1) 2α-hydroxy-O-methyl-pisiferic acid, (2) pisiferic acid, (3) O-methyl-pisiferic acid, (4) 12-methoxycarnosic acid, (5) carnosol and (6) salviol. b The proposed biosynthetic pathway of carnosic acid-family metabolites: Geranylgeranyl diphosphate (GGPP) is subjected to cyclization by a class II diterpene synthase to form copalyl diphosphate ((+)-CPP). Then, by the action of a class I diterpene synthase, miltiradiene is formed. Subsequent oxidation and cytochrome P450 activity results in the formation of ferruginol. Figure was produced using Chemescketch v 14.