Dietary Black Raspberries Impact the Colonic Microbiome and Phytochemical Metabolites in Mice

Abstract

Scope: Black raspberries (BRB) are a rich source of bioactive phytochemicals, including anthocyanins and ellagitannins. These phytochemicals are poorly absorbed and may be transformed by gut microbiota into various metabolites that may impact the colonic mucosa or upon absorption have systemic bioactivity. The objective of this study is to define the impact of a BRB-containing diet on the colon microbiome in mice and quantify the phytochemical metabolites in the colon contents and circulation.

Methods and results: Male mice were fed 10% w/w freeze-dried BRB powder for 6 weeks. The colonic microbiota was evaluated by 16S rRNA gene sequencing. Anthocyanin and ellagitannin metabolites, protocatechuic acid, and urolithins were analyzed by HPLC-MS/MS. The BRB diet impacted colon mucosal microbial composition with a more robust effect observed on the luminal microflora. BRB-derived protocatechuic acid and urolithins were quantified in the colon, luminal contents, plasma, liver, and prostate with protocatechuic acid present in higher concentrations compared to urolithins.

Conclusion: This study highlights the complex interactions between dietary phytochemicals, the host microbiome, and metabolism. It is demonstrated that microbially produced phytochemical metabolites are present in the colon and systemic circulation where they may exert biological activity.

Keywords: anthocyanins; black raspberry; ellagitannins; gut microbiota; metabolites; urolithins.