Advance in dietary polyphenols as dipeptidyl peptidase-IV inhibitors to alleviate type 2 diabetes mellitus: aspects from structure-activity relationship and characterization methods

Dietary polyphenols with great antidiabetic effects are the most abundant components in edible products. Dietary polyphenols have attracted attention as dipeptidyl peptidase-IV (DPP-IV) inhibitors and indirectly improve insulin secretion. The DPP-IV inhibitory activities of dietary polyphenols depend on their structural diversity. Screening methods that can be used to rapidly and accurately identify potential polyphenol DPP-IV inhibitors are urgently needed. This review focuses on the relationship between the structures of dietary polyphenols and their DPP-IV inhibitory effects. Different characterization methods used for polyphenols as DPP-IV inhibitors have been summarized and compared. We conclude that the position and number of hydroxyl groups, methoxy groups, glycosylated groups, and the extent of conjugation influence the efficiency of inhibition of DPP-IV. Various combinations of methods, such as in-vitro enzymatic inhibition, ex-vivo/in-vivo enzymatic inhibition, cell-based in situ, and in-silico virtual screening, are used to evaluate the DPP-IV inhibitory effects of dietary polyphenols. Further investigations of polyphenol DPP-IV inhibitors will improve the bioaccessibility and bioavailability of these bioactive compounds. Exploration of (i) dietary polyphenols derived from multiple targets, that can prevent diabetes, and (ii) actual binding interactions via multispectral analysis, to understand the binding interactions in the complexes, is required.