Derivatization of Soyasapogenol A through Microbial Transformation for Potential Anti-inflammatory Food Supplements

Abstract

For the optimum use of soyasaponins isolated from soybean cake and to explore the potential anti-inflammatory agents from pentacyclic triterpenes as natural food supplements, microbial transformation of soyasapogenol A was carried out. Four strains of microbes, including <i>Bacillus megaterium</i> CGMCC 1.1741, <i>Penicillium griseofulvum</i> CICC 40293, <i>Bacillus subtilis</i> ATCC 6633, and <i>Streptomyces griseus</i> ATCC 13273, showed robust catalytic capacity to the substrate. Preparative biotransformation and column chromatographic purification led to the isolation of 10 novel and 1 reported metabolites. The structure elucidation was performed using 1D/2D NMR and HR-ESI-MS analytical method. Several novel tailoring reactions, such as allyl oxidation, C-C double bond rearrangement, hydroxylation, dehydrogenation, and glycosylation, were observed in the biotransformation. In the follow-up bioassay, most of the metabolites exhibited low cytotoxicity and potent inhibitory activity against the production of nitric oxide (NO) in RAW 264.7 cells stimulated by lipopolysaccharide. Especially compound <b>6</b> (3-oxo-11α,21β,22β,24-tetrahydroxy-olean-12-ene) showed comparable activity to the positive control of quercetin with an IC₅₀ value of 16.70 μM. These findings provided an experimental approach to achieve the derivatization of natural aglycons in soybeans through microbial transformation for developing potent anti-inflammatory food supplements.