Effects of tea polyphenols and different teas on pancreatic α-amylase activity in vitro

•TP had mild inhibitory effect against α-amylase at high concentrations.•Enzyme activity was different when TP was pre-incubated with α-amylase or starch respectively.•Green tea, black tea and oolong tea all improved α-amylase activity.•Drinking tea could help starch digestion.

The effects of tea polyphenols (TP) and different types of teas (green, black and oolong tea) processed from the same fresh leaves on pancreatic α-amylase activity were studied using potato starch and cooked potato as substrates. The results showed that, with the both substrates, low concentration of TP significantly increased α-amylase activity while high concentration inhibited it by non-competitive fashion. In addition, the extents of enzymatic activation and inhibition were different when TP was pre-incubated with α-amylase or starch, respectively. The interaction of TP with enzyme/starch led to decreased antioxidant capacity. Results also showed that all the three types of teas significantly enhanced α-amylase activity for a wide range of concentrations (0.34-27.14 mg/mL), and green tea showed the highest activation effect. It is concluded that high concentration of TP exhibits mild inhibitory effect against α-amylase, while green tea, black tea and oolong tea enhance α-amylase activity, which may be due to other constituents in the tea, enhancing α-amylase activity that counteracts the inhibitory effect of TP.