Antihyperglycemic potential of fermented Digitaria exilis polysaccharide partially substituted with Clendendrum volubile leaf extract

Abstract

Digitaria exilis and Clendendrum volubile are underutilized food resources common in Africa. Clendendrum volubile leaf has a history of being used in traditional medicine to treat or manage hyperglycemia. Despite Clendendrum volubile nutritive and pharmaceutical significance, no scientific study has explored its application in functional food development. In this study, the inhibitory activities of Clendendrum volubile leaf extract (CVLE) against $\alpha$-amylase and $\alpha$-glucosidase was determined. Fermented Digitaria exilis polysaccharide (FDEP) was partially substituted with CVLE at different percentages (0.8 % and 1.2 %) and its antihyperglycemic effect was investigated in alloxan-induced diabetic rat models. Results showed that the IC₅₀ (CVLE extract concentration causing 50 % enzyme inhibition) for $\alpha$-amylase and $\alpha$-glucosidase were 330 $\mu g$/mL and 120 $\mu g$/mL, respectively, compared to acarbose, a standard inhibitor of starch-digesting enzymes, which had IC₅₀ values of 370 $\mu g$/mL and 170 $\mu g$/mL for $\alpha$-amylase and $\alpha$-glucosidase, respectively. The animal study showed that FDEP containing 0.8 % CVLE lowered the blood glucose level of diabetic rats by 45.31 % after 24 days. Increasing CVLE concentration in the FDEP to 1.2 % not only reduced blood glucose by 72.97 % after 24 days, comparable to metformin's 74.29 % reduction, but also alleviated body weight loss and improved liver function by lowering alanine transaminase, aspartate transaminase, and alkaline phosphatase.