In vitro antibacterial potential of acetone leaf extract of Otostegia integrifolia Benth against human selected bacterial pathogens

Abstract

Otostegia integrifolia Benth (O. integrifolia) is the endogenous medicinal plant of Ethiopia mostly used for the treatment of Stomach ache, tonsillitis, hypertension, malaria, ascariasis, and lung diseases. The current study was focused on phytochemical analysis and evaluation of the antibacterial activity of O. integrifolia Benth leave extracts against selected human bacterial pathogen by the agar well diffusion and microtube broth dilution method. Plant leaves were extracted with less polar to high polar solvents such as petroleum ether, chloroform, acetone, and ethanol. Phytochemical investigation was carried out for the identification of secondary metabolites responsible for antibacterial activity. In vitro antibacterial potential of O.integrifolia Benth leaf organic extracts against human pathogenic gram-negative (E. coli, K. pneumonia, V. cholera) and positive bacteria (B.subtilis, E. faecalis, S.aureus) were assessed by agar well diffusion, and bacterial inhibitory concentration of effective plant extracts was determined by 96 well plate broth dilution assay. Among all the tested organic leaf extracts, the acetone leaf extract of O.integrifolia Benth exhibited a promising broad spectrum of in vitro antibacterial activity against all tested multiple drug-resistant bacteria pathogens with significant MIC values of K.pneumoniae (2.144µg/ml), V. cholera (2.025µg), B.substilis (2.604 µg), and S.aureus (3.028 µg), respectively. The significant antibacterial activity of acetone leaf extracts of O. integrifolia Benth was due to the existence of flavonoids and phenolic compounds. The current studies demonstrated that the broad-spectrum antibacterial activity of acetone leaf extracts of O.integrifolia Benth might be helpful for the isolation of novel potent antibacterial agents against infectious bacterial pathogens without any side effects.