Alpha-Glucosidase Inhibition and Molecular Docking of Isolated Compounds from Traditional Thai Medicinal Plant, Neuropeltis racemosa Wall

Wall. (Convolvulaceae) is wildly distributed in Asia. Its stem is used as the component in traditional Thai recipes for treatments of muscle rigidity, skin disorder, dysentery, and hypoglycemia. However, the chemical constituents and biological activities of have not been reported. From a screening assay, stem crude extract showed the potent effect on alpha-glucosidase inhibition at 2 mg/mL as 96.09%. The bioassay-guiding isolation led to 5 compounds that were identified by spectroscopic techniques as scopoletin ( ), syringic acid ( ), methyl 3-methyl-2-butenoate ( ), feruloyltyramine ( ), and coumaroyltyramine ( ). Compounds , , and exhibited an IC of 110.97, 29.87, and 0.92 µg/mL, respectively, while the IC of positive standard, acarbose was 272.72 µg/mL. Kinetic study showed that compound performed as the mixed-type inhibition mechanism, whereas compounds and displayed the uncompetitive inhibition mechanism. The docking study provided the molecular understanding of isolated aromatic compounds ( , , and ) to alpha-glucosidase. Hence, this study would be the first report of isolated compounds and their anti-alpha-glucosidase activity with the mechanism of action from . Thus, these active compounds will be further studied to be the lead compounds among natural antidiabetic drugs.