In Vitro Alpha Glucosidase Activity of Uncaria gambir Roxb. and Syzygium polyanthum (Wight) Walp. from West Sumatra, Indonesia

BACKGROUND: Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia that occurs due to abnormal insulin secretion, insulin action, or both. Alpha-glucosidase enzyme inhibitors are drugs that work by slowing the absorption of carbohydrates in the intestine so that it has an impact on decreasing post-prandial glucose levels. AIM: The aim of the study was to assess the alpha-glucosidase inhibitory activities of methanolic extracts from different parts of Uncaria gambir Roxb. and Syzygium polyanthum (Wight) Walp. grown in Padang, West Sumatera, Indonesia often used as herbal medicine. MATERIALS AND METHODS: Methanolic extracts from different parts, fractions, and different drying methods of U. gambir Roxb. and S. polyanthum (Wight) Walp. grown in Padang, West Sumatera, Indonesia, were prepared for alpha-glucosidase inhibitory activities. RESULT: The proanthocyanidin fraction of U. gambir Roxb. (purity of ≥ 75%) showed a potent alpha-glucosidase inhibitory activities as evidenced by low IC50 at 28,993 ± 1,377 μg/ml, while (+)-catechin at 30,855 ± 0,791 μg/ml (IC50 acarbose: 111,286 ± 2,386 μg/ml). The Butanol fraction of S. polyanthum (Wight) Walp. showed potent alpha-glucosidase inhibitory activities as evidenced by low IC50 at 28,469 ± 1,929 μg/ml. CONCLUSION: Butanol fraction from U. gambir Roxb.’s oven-dried leaves and S. polyanthum (Wight) Walp. leaves contained proanthocyanidin class compounds. The proanthocyanidin fraction with a purity of > 75% had a stronger alpha-glucosidase inhibitory activity than the acarbose as a positive control.