Pu-erh tea polysaccharides decrease blood sugar by inhibition of α-glucosidase activity in vitro and in mice

Type 2 diabetes is mainly induced by environmental factors such as being overweight, decreased physical activity and inbalanced energy metabolism, such as pancreatic beta-cell dysfunction and peripheral insulin resistance. Acarbose, a microbial carbohydrate and an alpha-glucosidase inhibitor, is currently a useful agent for attenuating type 2 diabetes. However, it is usually accompanied by many side effects, such as abdominal distention, flatulence, diarrhea and meteorism. These side effects may be caused by its strong inhibition of alpha-amylase, leading to the accumulation of several undigested carbohydrates. The bacteria residing in the colon can further ferment the undigested carbohydrate to release gas. Finding a new alpha-glucosidase inhibitor with a low inhibitory effect on alpha-amylase is highly anticipated. In this report we describe a group of carbohydrates found in pu-erh tea polysaccharide (PTPS) that can inhibit alpha-glucosidase but have less of an inhibitory effect on alpha-amylase. The preliminary experiments on mice indicate that PTPS might be better than acarbose at suppressing blood glucose after oral administration of a carbohydrate diet; it is recommended that further clinical trials are required in type 2 diabetes in future studies.