The Antidiabetic Efficacy of Combined Extracts from Two Continental Plants: Azadirachta indica (A. Juss) (Neem) and Vernonia amygdalina (Del.) (African Bitter Leaf)

Abstract

Polyherbal therapy is said to be a current pharmacological principle having the advantage of producing maximum therapeutic efficacy with minimum side effects. We assessed the antidiabetic efficacy and hence the impact on biochemical indices of toxicity by a combination of extracts from neem and bitterleaf. Thirty rats, 25 diabetic and 5 non-diabetic rats, were used for the study. The diabetic rats were divided equally into five groups and respectively treated: saline (diabetic control), extracts from neem and bitterleaf combined, neem only, bitterleaf only and chlorpropamide for a 24 day period. After oral administration of the first dose of extract (400 mg kg^-1 b.w.) and chlorpropamide (4.286 mg kg^-1 b.w.), blood glucose was monitored in vivo at various time intervals for 9 h, thereafter daily administration continued for 24 days. Whereas single dose treatment with neem only showed peak reduction (28.56%) an hour after, treatments with combined extracts, bitterleaf and chlorpropamide had their peak reductions all at the 7th hour (24.78, 47.31 and 60.51%, respectively). Percentage reductions in blood glucose relative to their initial values at the end of treatment were 71.05, 44.95, 88.63 and 75.83 for combined extract, neem, bitterleaf and chlorpropamide respectively. The decrease in blood glucose for the groups treated with combined extracts and bitterleaf only compared well (p<0.01) with chlorpropamide and non diabetic control, but not with neem alone. Determination of markers of hepatotoxicity in serum including GPT and GOT activities, total protein, albumin and urea indicated that, of the four treatments, neem provides the best protection against hepatic dysfunction. In the group treated with combined extracts these alternate selective advantages of neem and bitterleaf were expressed as a positive synergy, hence more beneficial than individual treatments.