Regio- and stereo-selective oxidation of β-boswellic acids transformed by filamentous fungi

Abstract

Biotransformation of 11-keto-β-boswellic acid (KBA) and acetyl-11-keto-β-boswellic acid (AKBA) catalyzed by two fungal strains (Cunninghamella elegans AS 3.1207 and Penicillium janthinellum AS 3.510) was performed in the present investigation. Eleven transformed products (1–11) were isolated, and accurately identified by various spectral methods. Among them, eight products (1–4 and 8–11) are novel. Two microorganisms used in our experiments demonstrated the favourable capability of stereo- and regio-hydroxylation at the non-active position for boswellic acid skeletons (KBA and AKBA). P. janthinellum AS 3.510 preferred to catalyze hydroxylation reaction at the C-21α position, especially for AKBA with a yield of 35.7%. Meanwhile, C. elegans AS 3.1207 preferred to catalyze the hydroxylation reaction of C-21β, especially for KBA with a yield of 55.2%. The major metabolite 1 exhibited potent anti-inflammatory activity in the in vitro bioassay.