Comparative Antibacterial Study of Aqueous and Ethanolic Leaf Extracts of Annona Muricata

Abstract

This research project was aimed at investigating the antibacterial efficacy of aqueous and ethanol leaf extracts of A. muricata using agar-disc diffusion method for five clinical isolates of bacteria consisting of two gram-positive (Staphylococcus aureus and Streptococcus mutans) and three gram-negative (Pseudomonas aeruginosa, Escherichia coli, Salmonella typhi) bacteria which have been implicated in the most common types of bacterial infections such as diarrhea, typhoid fever, tooth decay, etc. The antibacterial activity was measured by the diameter of zone of inhibition (mm) observed and the extracts were found to exhibit antibacterial activities against the test organisms with each organism showing different patterns of formation of zones of inhibition at different concentrations of the extracts. The results of this study revealed that S. aureus was the most susceptible gram-positive bacteria and S. typhi was the most susceptible gram-negative bacteria which indicated that this plant contains compounds with wide antibacterial activity which validates their use for treatment of various microbial infections in traditional medicine. The findings in this study provide the basis for further study on the plant with the aim of isolating and identifying the active substances responsible for its antimicrobial activities. The plant could also be standardized to develop cheap, safer, culturally acceptable herbal medicines to help combat the problem of antibiotic resistance. The extraction of A.muricata which was done by maceration yielded 14.95% and 17.63% for aqueous and ethanol extracts respectively.The difference between both extracts when compared to the standard antibiotic(Ciprofloxacin) was significant(p<0.05 level of significance) against P.aeroginosa, E coli and S.mutans.Conversely, S aureus and S.typhi showed no significant difference(p<0.05 level of significance) in their response to both extracts(400 mg/ml) and the standard drug.This shows that A.muricata extract can be  potential antimicrobial agent directed against S.aureus and S.typhi.

Keywords: Annona muricata, antibacterial, extracts, comparative, ethno-medicinal.