In Vitro Evaluation of alpha-amylase and alpha-glucosidase Inhibition of 2,3-Epoxyprocyanidin C1 and Other Constituents from Pterocarpus erinaceus Poir

Diabetes mellitus is a metabolic disorder which is one of the leading causes of mortality and morbidities in elderly humans. Chronic diabetes can lead to kidney failure, blindness, limb amputation, heart attack and stroke. Physical activity, healthy diets and medications can reduce the incidence of di-abetes, so the search for more efficient antidiabetic therapies, most especially from natural products, is a necessity. Herein, extract from roots of the medicinal plant Pterocarpus erinaceus was purified by column chromatography and afforded ten compounds which were characterized by EIMS, HR-FAB-MS, 1D and 2D NMR techniques. Amongst them were, a new trimeric derivative of epicatechin, named 2,3-Epoxyprocyanidin C1 (1); two pentacyclic triterpenoids, friedelin (2) and betulin (3); angolensin (4); flavonoids such as 7-methoxygenistein (5), 7-methoxydaidzein (6), apigenin 7-O-glucoronide (8) and naringenin 7-O-beta-D-glucopyranoside (9); andan ellagic acid derivative (10). The extract and compounds were evaluated for their antidiabetic potential by oc-amylase and oc-glucosidase inhibitory assays. IC50 values of compound 7 (48.1 +/- 0.9 u.g/mL), compound 8 (48.6 +/- 0.1 u.g/mL), compound 9 (50.2 +/- 0.5 u.g/mL) and extract (40.5 +/- 0.8 u.g/mL) when compared to that of acarbose (26.4 +/- 0.3 u.g/mL) indicated good oc-amylase inhibition. In the oc-glucosidase assay, the extract (IC50 = 31.2 +/- 0.1 u.g/mL), compound 7 (IC50 = 39.5 +/- 1.2 u.g/mL), compound 8 (IC50 = 40.9 +/- 1.3 u.g/mL), compound 1 (IC50 = 41.6 +/- 1.0 u.g/mL), Compound 4 (IC50 = 43.4 +/- 0.5 u.g/mL), compound 5 (IC50 = 47.6 +/- 0.9 u.g/mL), compound 6 (IC50 = 46.3 +/- 0.2 u.g/mL), compound 7 (IC50 = 45.0 +/- 0.8 u.g/mL), compound 9 (IC50 = 44.8 +/- 0.6 u.g/mL) and compound 11 (IC50 = 47.5 +/- 0.4 u.g/mL) all had moderate-to-good inhibitions, compared to acarbose (IC50 = 22.0 +/- 0.5 u.g/mL). The ability to inhibit oc-amylase and oc-glucosidase indicates that P. erinaceus and its compounds can lower blood glucose levels by delaying hydrolysis of carbohydrates into sugars, thereby providing a source of natural antidiabetic remedy.