Metabolic fate of black raspberry polyphenols in association with gut microbiota of different origins in vitro

Polyphenols, ubiquitous in plant-originated foods, exhibit multifarious health benefits but are notorious for their low bioavailability. As the majority of polyphenols enter the colon where they are metabolized into the more bioavailable metabolites with multifarious bioactivities, gut microbiota composition is critical for realizing the health benefits of polyphenols. Black raspberries (BRB) are highly abundant in health-promoting but poorly absorbable polyphenols, primarily ellagitannins and anthocyanins. This study aimed to dissect the bilateral interactions between polyphenols and gut microbiotas of diverse origins. Using an optimized extraction procedure, BRB polyphenols were first comprehensively characterized by UHPLC-QTOF-MS/MS. Next, in vitro anaerobic fermentations with microbiota from human adults, infants, rats, and mice were conducted for comparison of phenolic profile (by metabolomics) and microbiota composition (by 16S rDNA sequencing) before and after fermentation. Bioinformatics analysis further revealed unique polyphenol-microbiota interactions and identified several bacterial species that could potentially produce bioactive and bioavailable phenolic metabolites following BRB consumption.