RESUMO
OBJECTIVE: To determine the effects of saponins from Tribulus terrestris (STT) on small intestinal a-glucosidase and postprandial blood glucose levels in rats. METHOD: The inhibitory effects of STT on a-glucosidase extracted from small intestines in rats were carried out in vitro. The blood glucose levels were measured after 60 min when sucrose (2 g x kg(-1)) or glucose (2 g x kg(-1)) was administered orally with STT (100 mg x kg(-1)). After treated with STT (100 mg x kg(-1)) for 14 d, the activities of a-glucosidase were determined daily, as well as the postprandial blood glucose levels after oraly administered sucrose (2 g x kg(-1)). RESULT: STT at concentrations of 0.1, 1 and 10 mg x mL(-1) reduced significantly the activities of alpha-glucosidase with inhibitory rates of (20.83 +/- 1.66)%, (43.73 +/- 2.39)% and (52.62 +/- 2.69)%, respectively. In facts STT (100 mg x kg(-1)) considerably decreased the blood glucose levels which was 52.61% of that of the control in rats co-administered orally with sucrose (2 g x kg(-1)). However, it showed no such effect on the rats co-administered orally with glucose (2 g x kg(-1)). After orally administered of STT for 14 d, the activity of alpha-glucosidase was significantly reduced (P < 0.05) to (58.17 +/- 3.24)% of that those in control. Meanwhile, The rats were oral administered with sucrose, the increase of postprandial blood glucose levels were (69.50 +/- 4.28)% of that in control 60 min later ( P < 0.05). CONCLUSION: It was through inhibiting the activity of a-glucosidase in small intestines that STT significantly retarded the increase in postprandial blood glucose levels in rats.