Mushroom-Derived Phenolic Compounds as Emerging Prebiotic-like Modulators of Gut Microbiota, Intestinal Health, and Metabolism

Background/Objectives: Mushroom-derived phenolic compounds are gaining attention as bioactive molecules with potential roles in gut microbiota modulation, intestinal health, and metabolic regulation. Although mushroom polysaccharides are well established as fermentable substrates, the contribution of fungal phenolics to microbiota–host interactions remains less defined. This review aimed to critically analyse the evidence supporting mushroom-derived phenolic compounds as emerging prebiotic-like modulators of gut microbiota, intestinal function, and host metabolism. Methods: A narrative critical review was conducted using scientific literature retrieved from PubMed, Scopus, Web of Science, and Google Scholar. Studies addressing phenolic profiling in edible and medicinal mushrooms, gastrointestinal digestion, colonic fermentation, microbial biotransformation, gut microbiota modulation, intestinal barrier function, inflammation, and metabolic outcomes were considered. Particular attention was given to chromatographic and mass spectrometry-based studies, in vitro digestion/fermentation models, mechanistic studies, animal experiments, clinical trials, systematic reviews, and meta-analyses. Results: Current evidence shows that mushrooms contain diverse phenolic compounds, mainly phenolic acids such as gallic, protocatechuic, caffeic, p-coumaric, ferulic, vanillic, syringic, and cinnamic acids. Due to limited small intestine absorption, a substantial fraction of these compounds may reach the colon, where they undergo microbial biotransformation into smaller phenolic metabolites. These metabolites may influence microbial ecology, support beneficial taxa, modulate short-chain fatty acid production indirectly, attenuate oxidative stress and inflammatory signaling, and contribute to intestinal barrier integrity. However, most evidence derives from in vitro and preclinical studies, while human data remain limited and are mainly based on whole-mushroom interventions. Conclusions: Mushroom-derived phenolic compounds are promising prebiotic-like modulators within the microbiota–metabolite–host axis. Nevertheless, their specific contribution cannot yet be quantitatively distinguished from that of other mushroom constituents, particularly β-glucans, chitin, and other fungal polysaccharides, because most available evidence derives from whole-mushroom matrices, crude extracts, or polysaccharide-rich preparations rather than isolated phenolic fractions. Future studies should compare whole mushroom preparations, polysaccharide-rich fractions, and standardized phenolic-rich extracts, integrating metabolomics, microbiome profiling, and well-designed clinical trials to clarify the relative mechanistic and therapeutic relevance of mushroom phenolics. Future studies should use standardized phenolic-rich extracts, metabolomics, microbiome analysis, and well-designed clinical trials to clarify their mechanistic relevance, clinical significance, and translational potential.