α-Amylase and Protein Tyrosine Phosphatase 1B Inhibitory of Some Vietnamese Medicinal Plants Used to Treat Diabetes

In this study, the twenty-four ethyl acetate extracts of twenty-two medicinal plants, traditionally used in Vietnam as anti-diabetes agents, were investigated for α-amylase and protein tyrosine phosphatase 1B (PTP1B) enzymes inhibitory activity in vitro. The results indicated that, twelve materials (50.0%) showed moderate to strong inhibitory activity in α-amylase inhibitory activity with IC50 values ranging from 2.5 to 48.8 μg/mL; meanwhile, ten extracts (41.6%) could demonstrate PTP1B activity with IC50 values less than 30.5 μg/mL. Some plants presented interesting activities against both of α-amylase and PTP1B enzymes such as Catharanthus roseus, Carthamus tinctorius, Momordica charantia, Gynostemma pentaphyllum, Glycyrrhiza glabra, Smilax glabra, Psidium guajava (leave), and Rehmannia glutinosa. The study may provide a proof, at least in a part, for the ethno-medical use in diabetes disease of these plants.