Isolation of an Antibacterial Flavonoid Glycoside from the Leaves of Cineraria abyssinica

Abstract

The leaf extract of Cineraria abyssinica Sch. Bip. exA. Rich (Asteraceae) is locally used for the treatment of various ailments including diarrhoea. Previous study has shown that the total hydroalcoholic extract of the leaves of the plant possesses genuine antibacterial activity. The main aim of this study was, therefore, to determine the active principle(s) of the plant. Thus, chloroform, acetone and methanol fractions of the leaves of C. abyssinica were prepared and investigated for their in vitro antibacterial activities against 21 Gram-positive and Gram-negative bacterial strains by agar disc diffusion method. It was found that all the fractions possess various degrees of antimicrobial activities against most of the bacteria tested. Among the bacterial strains tested Bacillus species were less sensitive. Bioactivity-guided fractionation of the most active methanol fraction resulted in the isolation of the flavonoidal glycoside, rutin the structure of which was assigned on the basis of spectroscopic methods. Rutin showed potent antibacterial activity against the majority of the tested bacteria which was comparable to that of the standard drug ciprofloxacin. Therefore, the present study revealed for the first time the presence of an antimicrobial phytochemical in the leaves of C. abyssinica that scientifically validated the traditional use and its potential for the treatment of infectious diarrhoea.

Keywords: Cineraria abyssinica, Asteraceae, antibacterial, agar diffusion, rutin