In vitro anti-diabetic activity of selected herbal teas extracted with different methods

One of the therapeutic approaches for decreasing postprandial hyperglycemia is to delay digestion of carbohydrates by the inhibition of hydrolyzing enzymes, alpha-amylase and alpha-glucosidase, in the digestive tract. For finding biologically active alpha-glucosidase inhibitors several plant extracts and phytochemicals have been evaluated. Frequently used herbal teas for weight management and for anti-hyperglycemic effects in Turkey can have potent of hydrolyzing enzyme inhibitory activity. Therefore the aim of this study is to test the alpha-glucosidase and alpha-amylase inhibitory effects of six herbal tea that consumed for weight management in Turkey and to compare their effects when extracted with different methods. Leaves of Crataegus monogya (hawthorne), Vaccinium myrtillus (blueberry), Morus nigra (black mullberry), roots of Asparagus officinalis (asparagus), red flower of Trifolium pratense (red clover) and Plantago lanceolate (plantago) leaves were collected from local herbal markets and used for the preparation of extracts. Plants extracted with ethanol and water. Inhibition of a-glucosidase and alpha-amylase activity was determined spectrophotometrically and the results were expressed as % inhibition of enzyme activity. The alpha-amylase inhibition assay showed that the ethanolic extracts of Crataegus monogya, Vaccinium myrtillus and Trifolium pratense exhibited considerably alpha-amylase inhibition activity with IC50 at 13.85 mu g/mL, 24.52 mu g/mL and 28.64 mu g/mL respectively. Out of six ethanolic plant extracts Crataegus monogya and Morus nigra exhibited better alpha-glucosidase inhibition activity with IC50 at 10.39 mu g/mL, and 18.70 mu g/mL. The ethanolic extract of Crataegus monogya leaves exhibited the strongest inhibitory effect on enzymes while its tea exhibited weaker effect. The results obtained indicated that the extracts of Crataegus monogya and Vaccinium myrtillus could be good sources for further studies as anti-hyperglycemic agents.