ASSESMENT OF THE ANTIMICROBIAL PROPERTIES OF LEAVES OF STARCHYTAPHETA CAYENNENSIS PLANT AGAINST SELECTED HUMAN PATHOGENS

Abstract

Water, ethanol and n-hexane extracts of Stachytapheta cayennensis leaf were obtained using the cold extraction method. The antimicrobial activities of the leaf extract was evaluated against ten organisms namely Escherichia coli (ATCC 25922), Shigella dysenteriae, Candida albicans (ATCC 10231), Salmonella typhi (ATCC 14028), Staphylococcus aureus, Bacillus subtilis, Salmonella typhimurium, Salmonella enteritidis, Trichophyton mentagrophyte (ATCC) and Listeria monocytogenes. A concentration of 200mg/ml of the extract was used for this antimicrobial assay. The results showed that the ethanol extract had the highest level of inhibitory effect on the test pathogens out of the three extracts used with zones of inhibition ranging between 1.0±0.6 to 13.7± 3.8(mm). It inhibited eight out of ten pathogens. None of the extracts inhibited Salmonella typhi and Listeria monocytogenes. The highest zone of inhibition of 13.7±3.8(mm) was observed against Shigella dysenteriae. Zones of inhibition recorded with water and n-hexane extracts against the test isolates ranged from 6.7±1.8 to 10±1.2 and 2.3±1.5 to 11±2.1 respectively. The ethanol extract was used for the MIC and MBC assay. The MIC value for both fungal pathogens- Trichophyton mentagrophyte and Candida albicans was 100mg/ml while it was 150mg/ml for bacterial isolates except for Staphylococcus aureus which recorded a concentration of 200mg/ml. The rate of killing assay showed continued reduction in the microbial load over a period of 24 hours. Phytochemical tests carried out showed the presence of flavonoids, tanins, saponins, steroid, terpenoid and cardiac glycosides. The FT-IR analysis established the presence of various biologically active functional groups including: Primary and secondary amines, amides, nitro compounds, alkyl halides, alkanes, alkenes, aromatic carbon compounds, and carboxylic acids.