Antibacterial activity of different fractions of Berberis Libanotica isolated by liquid/liquid subfractionation

Abstract

Antimicrobial resistance is an increasing threat to human health. With the increase in bacterial resistance and the lack of new antibiotics, there is a need for new sources of antimicrobials. Plants are an important source for biologically active components. The genus Berberis encompasses a wide range of species that are known to possess antibacterial activities against different bacteria. However, the antibacterial activity of the plant B. libanotica has not been investigated yet. B. libanotica branches and leaves were ground and extracted with 90% methanol (method 1) or 80% ethanol (method 2). The crude extract was further subfractionated with hexane, ethyl acetate, chloroform (method 1)/ butanol (method 2) and water. The obtained fractions were tested for their antibacterial activity against Gram-positive and Gram-negative bacteria. The hexane fraction gave highest antibacterial activity against S. aureus was with a Minimum Inhibitory Concentration (MIC) of 0.46875 mg/ml using method 1. Using method 2, the lowest MIC for the hexane, ethyl acetate, and butanol fractions was 1.875 mg/ml and lowest MIC for the water fraction was 0.9375 mg/ml against S. aureus. The ethanol crude extract, the ethyl acetate, and the butanol fraction had an MIC of 0.9375 mg/ml against Salmonella species. The ethyl acetate and butanol fractions showed lowest MICs against E. coli. The mechanisms of resistance to beta-lactam antibiotics of the tested clinical strains were phenotypically detected using double-disk synergy testing for the detection of ESBL, AMpC, and carbapenemases. Resistance of Staphylococcus aureus to methicillin was detected using cefoxitin disk. B. libanotica extracts showed antibacterial activity against the tested strains irrespective of the strains resistance pattern. Further testing is needed to determine the active compounds and the mechanism of action of B. libanotica.