Recent progress in natural products as DPP-4 inhibitors

Diabetes mellitus is a chronic disease affecting patients' daily life and increasing patients' risk of other complication. Dipeptidyl peptidase-4 (DPP-4) is a serine aminopeptidase, which is one of the validated targets for Type 2 diabetes therapy due to its regulatory effect of incretin hormone. Seven DPP-4 inhibitors are commercially available nowadays on the market as Type 2 diabetes drugs. They are all chemically synthesized compounds with good therapeutic effects, but long-term safety remains unknown. On the other hand, nature provides a rich source for search of desired safe and effective medications; and actually more than half of the drugs on market are natural product related. Therefore, a systematic search for new DPP-4 inhibitors from nature sources seems to be of great utility for developing novel antidiabetic drugs. This review summarized recent progress of DPP-4 inhibitors from natural products, revealed that both pure natural products and the crude extracts of herbs or the hydrolyzates of proteins are active as DPP-4 inhibitors. Therefore, both could be served as useful clues for developing next generation of antidiabetes medicines via inhibiting DPP-4 activity.