This review presents the comprehensive knowledge about the bidirectional relationship between polyphenols and the gut microbiome. The first part is related to polyphenols' impacts on various microorganisms, especially bacteria, and their influence on intestinal pathogens. The research data on the mechanisms of polyphenol action were collected together and organized. The impact of various polyphenols groups on intestinal bacteria both on the whole "microbiota" and on particular species, including probiotics, are presented. Moreover, the impact of polyphenols present in food (bound to the matrix) was compared with the purified polyphenols (such as in dietary supplements) as well as polyphenols in the form of derivatives (such as glycosides) with those in the form of aglycones. The second part of the paper discusses in detail the mechanisms (pathways) and the role of bacterial biotransformation of the most important groups of polyphenols, including the production of bioactive metabolites with a significant impact on the human organism (both positive and negative).

The Interactions between Polyphenols and Microorganisms, Especially Gut Microbiota.

https://digital.csic.es/bitstream/10261/253598/1/Food%20Chem2022-Aleixandre.pdf

Understanding phenolic acids inhibition of α-amylase and α-glucosidase and influence of reaction conditions.

Understanding phenolic acids inhibition of α-amylase and α-glucosidase and influence of reaction conditions

Can starch-polyphenol V-type complexes be considered as resistant starch?

Essential moieties of myricetins, quercetins and catechins for binding and inhibitory activity against α-Glucosidase.

Background α-Amylase is a key enzyme of starch digestion, playing an important role in deciding glucose releasing amount. Inhibition of the enzyme activity by polyphenols is suggested as a potential approach in controlling starch digestion and regulating postprandial hyperglycaemia. Scope and approach α-Amylase inhibition by polyphenols results from polyphenol-enzyme binding interactions that have been characterized by inhibition kinetics, spectroscopy and thermodynamic analyses. To further elucidate the inhibition mechanism, making the inhibition visible, studies regarding biochemical, biophysical and molecular mechanisms are summarized. Key findings and conclusions Macroscopically, α-amylase inhibition causes retarded digestion of starchy substrates, visible from the production reaction color or fluorescence. Microscopically, detail inhibition kinetics reveals the inhibition types and theoretic interacting sites. X-ray diffraction (XRD) is powerful in extracting the binding modes (detail amino acid residues, polyphenol moieties and interaction forces involved in polyphenol-amylase interactions). Through polyphenol-amylase binding analysis by XRD and NOE correlation of polyphenol atoms by rotating-frame Overhauser enhancement spectroscopy (ROESY)-NMR, the contribution of intramolecular interactions between polyphenol ring-groups to the binding is evaluated. The key phenolic moieties for binding are also obtained by saturation transfer difference (STD)-NMR and/or molecular docking. Besides, by combing fluorescent properties and thermal stability of α-amylase, the enzyme conformational changes may be obtained. Additionally, following delayed starch digestion, α-amylase inhibition is indicated by retarded increase in blood glucose level and colonic fermentation properties of undigested starch. Conclusively, visible characterization helps to understand how a polyphenol develops the inhibitory activity, and to reasonably explore functional factors for alleviation of carbohydrate metabolism disorder.

Yueyi Wang

Papers

Inhibition of α-amylase by polyphenolic compounds: Substrate digestion, binding interactions and nutritional intervention