Microbial Transformation of Maslinic Acid for Potential Food Supplements against Sterile Inflammation

Abstract

The microbial transformation of maslinic acid (MA) was investigated for the screening of potential metabolites as anti-inflammatory food supplements. Six novel and two known metabolites were obtained. In the bioassay of lipopolysaccharide and high mobility group box-1 protein (HMGB1) stimulated nitric oxide production in RAW 264.7 cells, it was surprising to see that most of the metabolites showed selective inhibitory effects on the HMGB1 model. Among them, metabolites 6 (2α,3β,7β,21βtetrahydroxy-olean-12-en-28-oic acid) and 8 (2α,3β,23-trihydroxy-olean-12-en-28,29-dioic acid) exhibited the IC 50 values of 10.77 ± 2.87 and 11.52 ± 1.09 μM, respectively. Molecular docking further revealed the newly introduced hydroxyl groups on C-21/C-23 and a carboxyl group on C-29 via biotransformation may interact with the amino residue of Ser12, Lys39, and Glu43 in HMGB1. Thus, biotransformation of MA or related extracts would provide an applicable routine for obtaining dietary supplements that selectively target damage-associated molecular patterns that stimulate sterile inflammation.