Bioguided isolation of pentacyclic triterpenes from the leaves of Alstonia scholaris (Linn.) R. Br. growing in Egypt
Ethanolic and aqueous extracts of the leaves and flowers of Alstonia scholaris were evaluated for their antioxidant activity by investigating their effect on blood glutathione levels in alloxan-induced diabetic rats. The ethanolic extract of the leaves was the most active; therefore, its cytotoxicity against HepG2 cells was also tested. Promising GI50 values of 1.96, 4.34 and 4.65μgmL-1 were observed for the extract, its chloroform and ethyl acetate fractions, respectively. The chloroform active subfraction I (GI50=2.97μgmL-1) yielded betulin (1), betulinic acid (2) and ursolic acid (3) upon purification. Compounds 1-3 were identified using spectroscopic techniques and by comparison with reported data. GLC of unsaponifiable and saponifiable fractions of the hexane extract revealed β-sitosterol (7.37%) and n-tetracosane (54.4%) to be the major sterol and hydrocarbon components, respectively. Linoleic acid (48.89%) was the predominant fatty acid. © 2012 Copyright Taylor and Francis Group, LLC.
El-Askary, Hesham I.; El-Olemy, Mahmoud M.; Salama, Maha M.; Sleem, Amany A.; and Amer, Mahetab H., "Bioguided isolation of pentacyclic triterpenes from the leaves of Alstonia scholaris (Linn.) R. Br. growing in Egypt" (2012). Pharmacy. 451.