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

The effects of tea polyphenols (TP) and different types of teas (green, black and oolong tea) processed from the same fresh leaves on pancreatic alpha-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 alpha-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 alpha-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 alpha-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 alpha-amylase, while green tea, black tea and oolong tea enhance alpha-amylase activity, which may be due to other constituents in the tea, enhancing alpha-amylase activity that counteracts the inhibitory effect of TP. (C) 2015 Elsevier Ltd. All rights reserved.