In vitro antiglycation and hypoglycaemic effects of Syzygium cumini leaf extracts

Glycation is a prime mechanism responsible for chronic diabetic complications, a process which is enhanced under hyperglycaemia. Natural inhibitors of protein glycation and those which can lower postprandial blood glucose elevation are of utmost importance in minimising the damage caused by diabetes. One objective of this study was to assess the in vitro inhibitory effects of Syzygium cumini (SC) leaf extracts on protein glycation and α-glucosidase activity. The other objective was to identify the type of inhibition on α-amylase activity. SC leaf powder was sequentially extracted with hexane (H), ethyl acetate (E), methanol (M) and water (W). In vitro inhibitory effects of extracts on protein glycation, α-amylase and α-glucosidase enzymes were measured. M and W were the major fractions recovered [50.74 and 27.94 % (w/w), respectively] while H was the smallest fraction [7.35 % (w/w)] out of total yield. All extracts inhibited fructosamine formation, protein glycation and protein crosslinking at 2 mgmL-1. At 0.05 mgmL-1, fructosamine formation was inhibited in the presence of E, M and W while there was no significant inhibition with H. At 0.1 mgmL-1, antiglycation effect of the H extract was negligible while other extracts retained their effects. IC50 values of H, E, M and W extracts against α-glucosidase were 7.89, 3.11, 0.86 and 0.69 μgmL-1, respectively. A mixed type inhibitory effect was observed on α-amylase with E, M and W extracts. H extract did not inhibit α-amylase. In conclusion, the results provide evidence for antiglycation and hypoglycaemic effects of SC leaf extracts demonstrating better activities in E, M and W extracts.