Abstract:
The leaves of Corchorus olitorius have been found to suppress elevation of postprandial blood glucose levels in rats and humans and thus used in the management of type II diabetes. But not much is known scientifically about other species that are also well consumed in Nigeria. This study was therefore designed to investigate the inhibitory effect of extracts of five species of Corchorus on α- amylase and α- glucosidase, so as to provide an insight into the possible mechanism of their antidiabetic action and to know the specieswith the most antidiabetic potential. Aqueous extracts were prepared by extracting dried Corchorus spp leaf samples with distilled water (10:1 v/v) and the supernatant was collected for subsequent analysis. The total phenol, flavonoid, vitamin C contents and antioxidant properties of the extracts were then evaluated. Furthermore, the inhibitory effect of the extracts on α- amylase and α- glucosidase was determined and the physioactive phenolic constituents partially characterised using gas chromatography (GC). The study revealed that Corchorus olitorius had the highest phenolic (500.0mg/100g) and flavonoid (82. 8mg/100g) contents. It also exhibited the highest reducing activity (0.7mgAAE/g), Fe²+ chelating ability (EC50 = 1.3μg/ml) and inhibition of Sodium nitroprusside induced lipid peroxidation in rats’ pancreas (47.78%) and Corchorus bougoudo exhibited highest DPPH (EC50 = 6.1 μg/ml), NO˙ scavenging ability (EC50= 3.2μg/ml) and inhibition of Fe²+- induced lipid peroxidation in rats’ pancrease (30.99%). Furthermore, Corchorus olitorius had the highest inhibitory effect on α- amylase (IC50 = 1.7 mg/ml) and α- glucosidase (IC50 = 1.5 mg/ml). The GC partial characterisation of the Corchorus spp leaf samples revealed the presence of some phenolic phytochemicals. Hence, inhibition of α- amylase and α-glucosidase and antioxidant activity may be the possible underlying mechanism for the antidiabetic property of the leaves.
