In vitro assessment of anti-diabetic potential of 4 kinds of dark tea (Camellia sinensis L.) protein hydrolysates

The contributions of four kinds of dark tea (Camellia sinensis L.) proteins and their hydrolysates to hypoglycemic activity were investigated in vitro. Four kinds of water-extracted dark tea proteins were hydrolyzed with trypsin and Alcalase, respectively. The complete proteins had α-amylase inhibitory activity with half maximal inhibitory concentration (IC50) values ranging from 1.27 to 2.78 mg/mL. Most of the dark tea proteins and hydrolysates significantly inhibited α-glucosidase and dipeptidyl peptidase (DPP-IV), with IC50 values in the range of 0.0103-1.3114 mg/mL and 0.1000-1.3364 mg/mL, respectively. In general, Heimaojian (HMJ) and Qianliang (QL) hydrolysates displayed high α-glucosidase inhibitory activity, while HMJ, Fuzhuan (FZ), and Heizhuan (HZ) hydrolysates exhibited a strong ability to inhibit DPP-IV. This study demonstrates the potential of dark tea proteins and their hydrolysates as a source of functional food and medicine for the control of type 2 diabetes.