Results suggest that B. micrantha has hepatoprotective and anti oxidant potentials. However, further work involving fractionation needs to done to isolate the active compound responsible for the hepatoprotective activity.
Aim: Acute and subchronic toxicity studies were performed on Gnetum africanum Welw leaves using well-established guidelines and methods. In spite of its use as a herbal remedy, there is a dearth of data on toxicity studies of the plant extract. Method: Gnetum africanum leaves were identified by a plant taxonomist, air-dried, pulverized, and extracted with 80% methanol for 48 hours in July 2015. The extract was concentrated in-vacuo and stored as Gnetum africanum extract (GAE) at 4°C. Thirty-five male albino rats randomly divided into seven groups (n = 5) were used for acute toxicity test, which was done in August 2015. Rats in groups 1-6 were given GAE at 500, 1,000, 2,000, 3,000, 4,000 and 5,000 mg/kg, respectively, while group 7 rats received 10 ml/ kg distilled water. Feed and water were provided and they were observed for signs of toxicity for 48 hours. A 90-day subchronic toxicity study was conducted using 56 rats of four groups (n = 14) in December 2015-March, 2016. Group 1 received feed without GAE, while groups 2-4 were given feed with GAE at 10, 20 and 40 mg/kg respectively. Four rats from each group were bled on days 30, 60, and 90 for clinical biochemistry and sacrificed for histopathological examination. Result: The median lethal dose (LD 50 ) was greater than 5,000 mg/kg while no-observed-adverse-effect-level was 40 mg/kg. Serum marker enzymes and creatinine were not increased in rats given extract in feed, while there were no histopathological lesions in the organs studied. Conclusions: The extract is safe at both the acute and subchronic levels.
ARTICLE HISTORY
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.
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