Microbial transformation of acetyl-11-keto-β-boswellic acid and their inhibitory activity on LPS-induced NO production.

Abstract The capabilities of 20 strains of fungi to transform acetyl-11-keto-β-boswellic ( AKBA ) were screened. And biotransformation of AKBA by Cunninghamella blakesleana AS 3.970 afforded five metabolites ( 1 – 5 ), while two metabolites ( 6 , 7 ) were isolated from biotransformation of Cunninghamella elegans AS 3.1207. The chemical structures of these metabolites were identified by spectral methods including 2D NMR and their structures were elucidated as 7β-hydroxy-3-acety-11-keto-β-boswellic acid ( 1 ), 21β-dihydroxy-3-acety-11-keto-β-boswellic acid ( 2 ), 7β,22α-dihydroxy-3-acety-11-keto-β-boswellic acid ( 3 ), 7β,16α-dihydroxy-3-acety-11-keto-β-boswellic acid ( 4 ), 7β,15α-dihydroxy-3-acety-11-keto-β-boswellic acid ( 5 ); 7β,15α,21β-trihydroxy-3-acety-11-keto-β-boswellic acid ( 6 ) and 15α,21β-dihydroxy-3-acety-11-keto-β-boswellic acid ( 7 ). All these products are previously unknown. Their primary structure–activity relationships (SAR) of inhibition activity on LPS-induced NO production in RAW 264.7 macrophage cells were evaluated.