Dipeptidyl peptidase IV inhibitory dipeptides contained in hydrolysates of green tea grounds

Peptides inhibiting human dipeptidyl peptidase IV (hDPP-IV) have potential as functional food ingredients to help prevent type 2 diabetes. In the present study, we analyzed the hDPP-IV inhibitory dipeptides contained in the hydrolysates of green tea grounds. The IC50 values of 337 standard dipeptides were calculated for the hDPP-IV inhibition. Next, to reveal whether the top 17 dipeptides with IC50 values less than 0.1 mM were present in the hydrolysates, the tea grounds hydrolysates were analyzed by LC-MS. Among the 17 dipeptides, Val-Leu, Leu-Trp, Trp-Ile, Asn-His, Thr-His, Thr-Trp, Trp-Ala, and Trp-Val were identified in the hydrolysates as novel hDPP-IV inhibitory dipeptides. Val-Leu particularly inhibited hDPP-IV (IC50: 0.074 mM) and was the most abundant (558 µg/g). These results suggest that green tea grounds are a promising dietary source for generating inhibitory peptides of hDPP-IV.