Gut Microbiota-Dependent Metabolism of 6-Shogaol Generates Bioactive Metabolites That Mediate Its Anti-Inflammatory Effects

Abstract

a 6-Shogaol (6S), a major bioactive constituent of ginger, exhibits anti-inflammatory activity, but the contribution of gut microbiota to its metabolism and biological effects remains unclear. Using germ-free (GF) and specific pathogen-free (SPF) mice, we demonstrate that gut microbiota play an essential role in the in vivo metabolism of 6S and the generation of bioactive metabolites. Two previously unreported metabolites were isolated from fecal samples, structurally characterized by high-resolution LC-MS/MS and NMR spectra, and confirmed by chemical synthesis. The most potent faecal fraction (Fraction 4), enriched in microbial metabolites of 6S, significantly suppressed nitric oxide production by 75%, reduced inducible nitric oxide synthase (iNOS) expression by 22% and cyclooxygenase-2 (COX-2) expression by 64%, and inhibited NF-κB p65 activation by 67% in lipopolysaccharide-stimulated RAW 264.7 macrophages. Moreover, intrarectal administration of microbial metabolites of 6S markedly attenuated LPS-induced inflammatory responses in mice by inhibiting TNF-α and IL-6 levels, with effects comparable to or exceeding those of 6S. Collectively, these findings demonstrate gut microbiota extensively metabolize 6-shogaol and its microbial metabolites still harbor anti-inflammatory activity.