Abstract
The α-glucosidase inhibitory activity of an aqueous extract and compounds from the aerial parts of V. corymbosa was demonstrated with yeast and rat small intestinal α-glucosidases. The aqueous extract inhibited yeast α-glucosidase with a half maximal inhibitory concentration (IC50) of 28.6 μg/mL. Bioassay-guided fractionation of the extract led to the isolation of several compounds, including one cyanogenic glycoside [prunasin (1)], five flavonoids [(−)-epi-catechin (2), hyperoside (3), isoquercetin (4), quercitrin (5) and quercetin-3-O-(6′′-benzoyl)-β-galactoside (6)] and two simple aromatic compounds [picein (7) and methylarbutin (8)]. The most active compound was 6 with IC50 values of 30 μM in the case of yeast α-glucosidase, and 437 μM in the case of the mammalian enzyme. According to the kinetic analyses performed with rat and yeast enzymes, this compound behaved as mixed-type inhibitor; the calculated inhibition constants (Ki) were 212 and 50 μM, respectively. Molecular docking analyses with yeast and mammalian α-glucosidases revealed that compound 6 bind differently to these enzymes. Altogether, the results of this work suggest that preparations of V. corymbosa might delay glucose absorption in vivo.
Highlights
Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder whose prevalence has been increasing steadily all over the world [1]
An aqueous extract (AE) of V. corymbosa inhibited in a concentration-dependent manner (IC50 = 28.5 μg/mL) the enzymatic activity of yeast α-glucosidase when tested by a well-known spectrophotocolorimetric assay [11]
Fractionation of the active extract led to the isolation of one cyanogenic glycoside [prunasin (1) [12,13]], several flavonoids [(−)-epi-catechin (2) [14], hyperoside
Summary
Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder whose prevalence has been increasing steadily all over the world [1]. The best treatment for T2DM is based on an adequate control of the hyperglycemia condition, which is possible to achieve with a healthy lifestyle and appropriate pharmacological therapies [4]. These treatments include drugs that promote insulin secretion (sulfonylureas) or utilization (biguanides and thiazolidinediones) and, drugs that reduce the rate of carbohydrate absorption from the gastrointestinal tract and decrease postprandial glucose peak [4]. The latter group includes α-glucosidase inhibitors, of which acarbose and miglitol are the most widely used [5,6]. In recent years substantial efforts have been made to discover new natural effective α-glucosidase inhibitors useful for the development of new remedies; in this regard medicinal plants have shown to be valuable sources of these inhibitors [7]
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