Inter-species and individualized biotransformation of five saponins by human being- and mouse-derived fecal microbiota

BACKGROUND: The gut microbiota plays a critical role in the biotransformation of saponins. However, current research predominantly focuses on metabolism by single microbial species, with limited investigation into inter-species differences or inter-individual variability in saponin biotransformation, especially by the culture of mixed gut microbiota. This study aims to elucidate the species-specific differences and inter-individual variability in gut microbiota-mediated saponin biotransformation through multidimensional analysis. METHODS: In this study, we selected five representative saponins, including ginsenoside Rb1, ginsenoside Re, glycyrrhizic acid, saikosaponin D and dioscin, and conducted anaerobic cultures ex vivo with mixed gut microbiota derived from mice and humans. Metabolic profiles of parent compounds and their metabolites were analyzed using UPLC-MS/MS. Additionally, three saponins (ginsenoside Rb1, glycyrrhizic acid and saikosaponin D) were co-cultured with gut microbiota from 50 healthy volunteers to assess inter-individual biotransformation variability. 16S rRNA gene sequencing was employed to identify key microbial taxa and potential metabolic pathways. RESULTS: We revealed distinct biotransformation patterns of multi-component saponins by mixed gut microbiota, with notable inter-individual variability observed among 50 healthy volunteers. Particularly, ginsenoside Rb1 exhibited the most significant individual differences in gut microbiota biotransformation. Further analysis demonstrated that the biotransformation capacity of gut microbiota was closely correlated with both its taxonomic composition and the relative abundances of specific bacterial genera. CONCLUSION: This study elucidated the pivotal role of gut microbiota in mediating inter-individual differences in saponin biotransformation, while having identified potential microbial communities and metabolic pathways involved in saponin biotransformation. These findings not only advance understanding of species-dependent biotransformation of saponins but also establish a foundation for screening microbial strains or enzymes to optimize saponin-derived therapies, thereby facilitating precision medicine and translational research.