Abstract

This research aims to investigate the α-glucosidase (baker’s yeast and rat intestinal acetone powder) inhibitory potential of Diospyros kaki Thunb. (Ebenaceae) leaf extract (DKLE) along with its antioxidant activity against metal-catalysed protein oxidation by pro-oxidant model (Fe²⁺/ascorbate) in rat liver homogenates, in vitro. DKLE evidenced the outstanding inhibitory effect with IC₅₀ values of 1.22 and 32 µg/ml for baker’s yeast and rat intestinal α-glucosidase enzymes. The inhibition mode of this extract was determined by measuring enzyme activity in different concentrations of substrate for Lineweaver-Burk plot analysis. Its inhibition was found to be noncompetitive. The addition of Fe2+/ascorbate to the liver homogenate significantly increased the extent of lipid peroxidation which was significantly lowered with the extract treatment. Furthermore, DKLE ability to alleviate postprandial hyperglycemia in normal and streptozotocin (STZ)-induced diabetic rats was scrutinized. Oral administration of this leaf extract (250 to 1000 mg/kg body wt.) considerably decreased blood glucose in normal and diabetic rats after glucose and maltose loading in a dose-dependent manner. These results propose that DKLE might show an anti-diabetic effect by suppressing carbohydrate and glucose absorption from the intestine and can reduce the postprandial blood glucose rise.

Key words: Diospyros kaki, α-glucosidase, antioxidant, diabetic rats, postprandial hyperglycemia, streptozotocin.