Alleviating the Hydrolysis of Carbohydrates, Tangzhiqing (TZQ) Decreased the Postprandial Glycemia in Healthy Volunteers: An Eight-Period Crossover Study

Tangzhiqing (TZQ), a Chinese herbal medicine, has been widely used to treat diabetes mellitus in China. TZQ works as a potential α-glucosidase inhibitor to reduce the absorption of glucose from dietary carbohydrates. The main aim of this study was to investigate the postprandial glucose-lowering effect of TZQ on the common carbohydrates in healthy humans. Meanwhile, the possible types of the inhibited α-glucosidase enzymes were predicted in this study. Glucose, sucrose, maltose, maltodextrin, and starch were chosen as investigated carbohydrates. The baseline incremental area under the curve (IAUC) and glycemic index (GI) values of the investigated carbohydrates were evaluated. Then, thirty-six subjects were randomly assigned to three groups to assess postprandial hypoglycemic effects of 3-, 6-, and 9-tablet TZQ. The subjects in each group were randomized to eight subgroups. An eight-period, eight-sequence, crossover design was performed to investigate the postprandial glucose-lowering effect of TZQ after drinking each carbohydrate. A significant decrease was observed on the postprandial glucose IAUCs (279.41 ± 111.31 vs. 203.86 ± 61.08) and GIs (124.91 ± 48.54 vs. 91.69 ± 27.47) of maltose after oral administration of 6-tablet TZQ, as well as IAUCs (145.05 ± 55.01 vs. 110.23 ± 57.03) and GIs (84.87 ± 33.40 vs. 65.50 ± 33.89) of sucrose after administration of 3-tablet TZQ. The glucose IAUCs (109.15 ± 55.92 vs. 57.68 ± 46.09) and GIs (49.09 ± 25.15 vs. 25.94 ± 20.73) of starch statistically reduced following the administration of 6-tablet TZQ. The lowering postprandial blood glucose effect of TZQ did not increase proportionally with increasing doses in humans. There were no significant changes in the glucose-lowering effect of glucose and maltodextrin after the administration of 3-, 6-, or 9-tablet TZQ, respectively. TZQ is a potential treatment for postprandial hyperglycemia, which can probably make α-glucosidases inhibit maltase, sucrase, and α-amylase in the digestive organs.