11-Keto-beta-boswellic acid (KBA), as one of the active constituents in the gum resin of Boswellia serrata, possesses significant biological activities including anti-inflammatory activity. However, its extensive metabolism and low polarity has limited the systemic availability of KBA. The present research was aimed to obtain and explore the various possible derivatives of KBA through biotransformation by Cunninghamella blakesleana AS 3.970. A total of ten transformed compounds were isolated and purified, and their chemical structures were characterized as 7 beta-hydroxy-11-keto-beta-boswellic acid; 7 beta, 15 alpha-dihydroxy-11-keto-beta-boswellic acid; 7 beta, 16 beta-dihydroxy-11-keto-beta-boswellic acid; 7 beta, 16 alpha-dihydroxy-11-keto-beta-boswellic acid; 7 beta, 22 beta-dihydroxy-11-keto-beta-boswellic acid; 7 beta, 21 beta-dihydroxy-11-keto-beta-boswellic acid; 7 beta, 20 beta-dihydroxy-11-keto-beta-boswellic acid; 7 beta, 30-dihydroxy-11-keto-beta-boswellic acid; 3 alpha, 7 beta-dihydroxy-11-oxours-12-ene-24, 30-dioic acid and 3 alpha, 7 beta-dihydroxy-30-(2-hydroxypropanoyloxy)-11-oxours-12-en-24-oic acid by various spectroscopic methods. The biotransformation processes include hydroxylation, oxidation and esterification. Primary structure-activity relationships (SAR) of inhibitory effects on NO production in RAW 264.7 macrophage cells are discussed. (C) 2013 Elsevier Ltd. All rights reserved.