Bioactivity-guided fractionation of a methanol leaf extract from Gnetum africanum with potential anti-diabetic activity: (-)-Epicatechin as the active principle

Abstract

Dietary constituents of plants such as flavonoids are very important in ameliorating the challenges of metabolic disorders such as diabetes mellitus. The study evaluated the antidiabetic activities of fractions and a known flavonoid isolated from Gnetum africanum (Welw) of fasting blood sugar (FBS) in alloxan-induced diabetic albino rats. Antidiabetic activity-guided isolation by column chromatographic (CC) separation of methanol extract and purification of the most active CC fractions by semi-preparative high performance liquid chromatograpgy (HPLC) yielded a known flavonoid (GAF7.4) and four other uncharacterized fractions. The structure of GAF7.4 was elucidated based on the 1D and 2D NMR and HREIMS spectroscopic analyses. Antidiabetic activity was conducted by alloxan-induced FBS in diabetic rats model using glibenclamide as standard. The flavonoid (GAF7.4) was identified as (-)-epicatechin. The CC fraction 7 (50 mg/kg) elicited significant (p < 0.05) reduction in FBS of 42.3 % after 6 h. The isolated flavonoid (GAF7.4), 10 mg/kg dose caused a significantly higher reduction in FBS of 71.4 % in alloxan induced diabetic rats compared with 41.2 % reduction in glibenclamide (2 mg/kg) control. This represented the first report of epicatechin in G. africanum and our findings have contributed new knowledge to antidiabetic constitutents of the plants.

Antioxidants for the Prevention and Treatment of Non-communicable Diseases

“…Additionally, diabetes mellitus has been linked to increased formation of free radicals and a reduction in antioxidant activities, which also results in the imbalance between the generation of ROS and antioxidants, thus leading to oxidative damage to cell proteins, lipids, and nucleic acids. 11, 86 Glucose autoxidation is the most important factor in the generation of free radicals among the different variables that cause increased oxidative stress. Other factors also elevate the levels of pro-oxidants, imbalance in cellular oxidation, and a re-duction in antioxidant defense.…”