Biocatalysis of ursolic acid by the fungus CGMCC 3.3657 and resulting anti-HCV activity.

Biocatalysis of ursolic acid (UA 1) by CGMCC 3.3657 was investigated. Baeyer-Villiger oxidation was found to occur during the reaction. Four metabolites were isolated from the cultures and their structures were identified as 21-oxo,A-homo-3-oxa-urs-12-en-3-one-28-oic acid (2), 21-oxo-3,4-seco-ursan-4(23),12-dien-3,28-dioic acid (3), 21β-hydroxyl-A-homo-3-oxa-urs-12-en-3-one-28-oic acid (4) and 21β-hydroxyl-3,4-seco-ursan-4(23),12-dien-3,28-dioic acid (5), based on their NMR and MS spectral data. All of the four metabolites were new and their anti-HCV activity was tested. Their biotransformation pathway was also proposed.