Biotransformation of oleanolic and maslinic methyl esters by Rhizomucor miehei CECT 2749.

The pentacyclic triterpenoids methyl oleanolate, methyl maslinate, methyl 3ß-hydroxyolean-9(11),12-dien-28-oate, and methyl 2α,3ß-dihydroxy-12ß,13ß-epoxyolean-28-oate were biotransformed by Rhizomucor miehei CECT 2749. Microbial transformation of methyl oleanolate produced only a 7ß,30-dihydroxylated metabolite with a conjugated 9(11),12-diene system in the C ring. Biotransformation of the substrate with this 9(11),12-diene system gave the same 7ß,30-dihydroxylated compound together with a 7ß,15α,30-trihydroxyl derivative. The action of this fungus (R. miehei) on methyl maslinate was more varied, isolating metabolites with a 30-hydroxyl group, a 9(11),12-diene system, an 11-oxo group, or an 12-oxo group. Microbial transformation of the substrate with a 12ß,13ß-epoxy function resulted in the isolation of two metabolites with 12-oxo and 28,13ß-olide groups, hydroxylated or not at C-7ß, together with a 30-hydroxy-12-oxo derivative. The structures of these derivatives were deduced by extensive and rigorous spectroscopic studies.

Biotransformation of oleanolic and maslinic acids by Rhizomucor miehei.

Microbial transformation of oleanolic acid by Rhizomucor miehei produced three metabolites. A known compound, a 30-hydroxyl derivative (queretaroic acid), and two 7ß,30- and 1ß,30-dihydroxylated metabolites, respectively. The action of the same fungus (R. miehei) on maslinic acid produced an olean-11-en-28,13ß-olide derivative, a metabolite hydroxylated at C-30, an 11-oxo derivative, and two metabolites with an 11α,12α-epoxy group, hydroxylated or not at C-30. Their structures were elucidated by extensive analyses of their spectroscopic data, and also by chemical correlations.