Radical scavenging compounds from Ethiopian medicinal plants

Abstract

Various solvent fractions prepared from plants used in Ethiopian traditional medicine were examined for their potential radical scavenging activity using rapid TLC screening method. The preliminary results indicated that the methanol fractions of the leaves of Bersama abyssinica and the fronds of Cheilanthes farinose, and the acetone fraction of the leaves of Euclea racemosa ssp. schimperi possess significant free radical scavenging capacity. The abilities of these extracts to act as nonspecific donors of hydrogen atom or electrons were evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. It was found out that they all showed positive results with the methanol extract of B. abyssinica (7.5 ug/ml) displaying the highest activity. Phytochemical investigation of the methanol fraction of B. abyssinica leaves resulted in the isolation of five flavonol glycosides and the xanthone, magniferin. Four flavonol glycosides together with the plant acids caffeic acid and chlorogenic acid were obtained from the methanol extract of the fronds of Cheilanthes farinose. Similarly, the acetone fraction of the browse plant, E. racemosa ssp. schimperi afforded four flavonol glycosides. All the secondary metabolites isolated from these active fractions were found to exhibit significant antioxidant activity, as judged by scavenging stable DPPH free radicals. However, the flavonol glycoside rutin figured as the most active radical scavenger with an IC50 value of 9.5 mM.

Ethiopian Pharmaceutical Journal Vol. 24, 2006: 23-30