Evaluation of the antibacterial activity of Launaea cornuta extracts

Abstract Background Medicinal plants have been used time immemorial to treat various ailments and diseases caused by pathogenic microorganisms attributed bioactive compounds they contain. Such compounds may have developed in plants as self-defense mechanism against pests and pathogens purposely to survive and perpetuate themselves in their ecosystem. A few studies have been conducted on L. cornuta. The study sought to determine the effect of L. cornuta leaf, stem bark and root extracts against selected bacteria. Methods Methanol, Dichloromethane and Aqueous extracts of L. cornuta were tested for bacteriostatic and bactericidal effects against Escherichia coli ATCC 27853, Shigella dysenteriaea ATCC 13313 and Pseudomonas aeruginosa, Staphylococcus aureus ATCC 25923. Phytochemical screening of the extracts was performed using thin layer chromatography (TLC) with Ethyl acetate: petroleum spirit at the ratio of (3:7) as the solvent system for dichloromethane extracts while dichloromethane: methanol ratio (9.5: 0.5) solvent system was utilized for methanol extracts. Cytotoxicity of the active extracts was determined using Vero E6 cell lines. The cell cytotoxicity levels were read using an ELISA scanning Multiwell spectrophotometer (Multiskan Ex Labssytems, Thermo Fisher Scientific, USA) at 562 nm and 620 nm as reference. The cytotoxic concentration responsible for lysis and death of 50% of the cells was determined using Microsoft Office Excel 2007 software by linear regression analysis. Results Stem, leave and root extracts showed weaker / little or no activity with zone diameter inhibition < 10mm against the selected bacteria. No activity was observed with S. aureus. Minimum inhibitory concentration (MIC) value of extracts ranged between 500mg/ml to 60 mg/ml. DCM stem bark extracts had MIC value of 62.5 mg/ml against S. dysenteriaea and 500mg/ml against S. aureus. The extracts were not cytotoxic at 1000 µg/ml which was the highest concentration tested except methanol leave extracts that were found to be moderately toxic at 493.5 µg/ml. Conclusions The study findings suggest that L. cornuta methanol, aqueous and dichloromethane extracts are moderately efficacious in the control of the selected bacteria.