Microbial transformation of ursolic acid by Syncephalastrum racemosum (Cohn) Schroter AS 3.264.

Biotransformation of ursolic acid by the filamentous fungus Syncephalastrum racemosum (Cohn) Schroter AS 3.264 yielded five metabolites. Their structures were identified as 3β,21β-dihydroxy-urs-11-en-28-oic acid-13-lactone, 3β,7β,21β-trihydroxy-urs-11-en-28-oic acid-13-lactone, 1β,3β-dihydroxy-urs-12-en-21-one-28-oic acid, 1β,3β,21β-trihydroxy-urs-12-en-28-oic acid and 11,26-epoxy-3β,21β-dihydroxy-urs-12-en-28-oic acid based on NMR and MS spectroscopic analyses. The condensation reactions to form 28-oic acid-13-lactone ring and 11,26-epoxy ring are not frequently seen for the biotransformation of triterpenoids. One compound showed moderate inhibitory activity against protein tyrosine phosphatase 1B (PTP1B).