Antihyperglycemic Activity of Alstonia scholaris R. Br. Leaf Extract in Streptozotocin Induced Diabetic Rats, the Relevance of Ursolic Acid

The objective of this research was to evaluate the antihyperglycemic activity of water soluble ethanolic extract of Alstonia scholaris R.Br. in streptozotocin induced diabetic rats. Streptozotocin induced (40 mg/kg, i.p.) diabetic rats were administered a single oral dose of water soluble ethanolic (70%) extract (200, 400, 600, 800 and 1000 mg/kg, p.o., n = 6/group) of Alstonia scholaris R. Br. leaves or vehicle (distilled water, 10 ml/kg, p.o.) or standard drug, glibenclamide (5 mg/kg, p.o.). Blood samples were collected by retro-orbital puncture at 1, 2, 3, 4 and 5 h after treatment and were analyzed for plasma glucose by glucose oxidase/peroxidase method. Plasma samples of the rat treated with the plant extract were analyzed by HPTLC using precoated silica gel60F₂₅₄ HPTLC plates with toluene-ethylacetate-methanol-triethylamine (7:2:1:1, v/v/v/v), as mobile phase [1]. The plant extract exerted significant (P < 0.05) hypoglycemic effect in streptozotocin-induced diabetic rats. The hypoglycemic effect of the extract at a dose 1000 mg/kg was comparable with that of glibenclamide (5 mg/kg, p.o.). In oral glucose tolerance test, aqueous extract of A. scholaris increased glucose tolerance. HPTLC analysis of the plasma samples of rats treated with the plant extract showed the presence of ursolic acid, a major triterpenoid (≈ 2%) of the plant [2,3]. Acknowledgement: Thanks to S.P. Mandalis Ramanarain Ruia for providing necessary facilities and to Dr. K.S. Laddha, MUICT for gift sample of ursolic acid. References: [1] Shetty P, et al. (2007), Journal of Planar Chromatography, 20(2): 117–120. [2] Dhar DN, et al. (1977), Planta medica, 31: 33–34. [3] Banerji A, Banerji J (1977), Indian Journal of Chemistry, Vol. 15B, p.390–391