Evaluation of antimicrobial activity and mode of action of Laportea aestuans extracts against urogenital, gut and pulmonary pathogens

Abstract

Phytochemical screening and antimicrobial activities of Laportea aestuans leaves, stem-bark and whole-plant aqueous, methanol and ethanol extracts were carried-out using standard phytochemical and microbiological methods. The phytochemical procedures indicated the presence of saponins, tannins, phlobatannins, flavonoids, alkaloids and cardiac-glycosides. The yields of the whole-plant extracts were significantly(p ethanol>methanol. The antimicrobial activities of the aqueous, methanol and ethanol extracts of Laportea aestuans leaves, stem-bark and whole-plant against the auchthocthonous urogenital, gut and pulmonary test organisms: Staphylococcus aureus , Staphylococcus saprophyticus , Streptococcus pneumoniae , Escherichia coli , Pseudomonas aeruginosa , Proteus mirabilis , Salmonella typhi , Vibrio cholerae , Shigella dysenteriae , Candida albicans and Aspergillus niger ; assayed by the modified agar-well diffusion technique indicated broad-spectrum antimicrobial activities. Analysis of the antimicrobial activities of the extracts by activity-index, indicated that the leaf extracts, have significantly (p stem-bark extracts >whole- plant extracts. Similarly by activity-index, the ethanol extracts recorded significantly (p methanol extracts>aqueous extracts. The minimum inhibitory concentrations (MIC) of the leaves extracts, assayed by the macrobroth-dilution technique was lowest against Shigella dysentariae ( 1.25 mg/ml),and generally between 2.50 - 5.0 mg/ml against the other bacterial and fungal species tested for both methanol and ethanol extracts; while the aqueous extracts was inactive. Equally, the minimum biocidal concentrations (MBC), and the establishment of mode of activity of the bioactive leaves extracts, assayed by the macrobroth-dilution technique, indicated predominantly static activity for the methanol extract, and a predominantly cidal activity for the ethanol extract. Both methanol and ethanol leaves extracts of Laportea aestuans showed significant (p<0.05) antimicrobial activities compared to the standard antibiotics: chloramphenicol and fluconazole. Keywords: Antimicrobial potency, Activity –spectra, Laportea aestuans Extracts, Auchthocthonous urogenital, gut and pulmonary pathogens