Antibacterial Activity of Guyabano, Ulasimang Bato, Sambong, and Tsaang Gubat Leaf Extracts against Common Drug-resistant Bacteria

Background. Using plants as antimicrobials has long been a practice of traditional healers and validating these customs may lead to the discovery and development of useful herbal medicines. Objective. This study aimed to determine the antibacterial activity of guyabano, tsaang gubat, sambong, and ulasimang bato against common pathogens. Methods. Aqueous or alcoholic leaf extracts of the different medicinal plants were prepared. The solid agar dilution method was used to determine the MIC of guyabano, tsaang gubat, sambong, and ulasimang bato against common pathogens including Staphylococcus aureus, Echerichia coli, Streptococcus pneumoniae, Hemophilus influenzae, Pseudomonas aeruginosa, Salmonella typhi, and Shigella flexneri. Results. The alcoholic leaf extract of guyabano showed moderate activity against oxacillin-sensitive S. aureus with an MIC of 5-6.3 mg/mL. However, tsaang gubat did not exhibit any antibacterial activity for drug-resistant enteric organisms (S. typhi, S. flexneri, and E. coli) and S. aureus at a concentration of 25 mg/mL. Even at a concentration of 100mg/mL, ulasimang bato failed to show any antibacterial activity against drug-resistant S. aureus, S. pneumonia, H. influenzae, E. coli, and P. aeruginosa. Sambong alcoholic extract had some antibacterial activity against penicillin-resistant S. pneumoniae with an MIC of 12.5 mg/mL. Conclusions. Guyabano alcoholic leaf extract showed moderate antibacterial activity against oxacillin-sensitive S. aureus. Sambong alcoholic extract likewise exhibited inhibitory activity against S. pneumoniae. However, tsaang gubat and ulasimang bato aqueous extracts failed to show significant antibacterial activity for the pathogens tested.