Differential modulation of gut microbiota by four fruit extracts revealed via in vitro digestion–colonic fermentation model

Fruits rich in polyphenols can regulate the gut microbiota ecology, but the differences in their effects among different fruits are unclear, and the interaction between polyphenols and the microbiota remains unexplained. This study investigated the regulatory effects of extracts from four fruits with different polyphenol compositions—red raspberry, hawthorn, blueberry, and mulberry—on the microbiota through in vitro digestion and simulated colonic fermentation. The study also validated the regulatory preferences of different extracts on microbial species using core microbiota. First, considering both changes in microbial species and the production of short-chain fatty acids, mulberry and blueberry extracts were more beneficial to the development of the microbiota ecology, followed by hawthorn and red raspberry. Subsequently, the abundance of 25 core microbial genera was analyzed, revealing significant species correlations in the regulation of microbial structure by the four extracts. For example, blueberry extract upregulated Bacteroides and Parabacteroides, and hawthorn extract enriched Limosilactobacillus. The differences in the regulatory effects of extracts on core species were validated using 10 core microbial strains derived from the feces of healthy individuals. Finally, Spearman correlation and network degree centrality were used to explore the relative strengths of the effects of different polyphenol subclasses on the core microbiota. Data showed that flavonoids had a stronger effect on the microbiome than phenolic acids, and the polyphenol subclasses with the greatest impact on the microbiome were, in descending order: Dihydroflavonols > Flavonols > Isoflavonoids > Hydroxycinnamic acids > Flavanols. Based on this, this study constructed an interaction network of "polyphenol-core microorganism-short-chain fatty acids" by associating 10 representative polyphenols with 25 core microbial genera to elucidate the interactions between polyphenols in extracts and core microbial species. These findings contribute to understanding the differences in the intervention effects of different fruit polyphenols on the microbiome, as well as the targeted regulatory effects of specific polyphenols on microorganisms.