Modulation effect of Herbal extracts on the antibacterial activity of Tetracycline

Abstract

As part of our ongoing study to screen local herbs for their possible usefulness in chemotherapy of infectious diseases, we assessed extracts from sixteen herbs for their antimicrobial properties and their influence on the activity of tetracycline. The minimum inhibitory concentrations (MIC) of tetracycline against Staph. aureus, B. subtilis, P. aeruginosa, E. coli and S. typhi were determined alone and in the presence of sub-inhibitory concentrations of the extracts by the Kirby–Bauer agar diffusion method of antibacterial assay. Twelve of the extracts potentiated the antibacterial activity of tetracycline against at least one of the test bacteria. Extracts of B. arundinacea, B. pilosa, C. membranaceus, E. guineensis, H. sabdariffa, J. curcas root, M. oppositifolius, M. lucida and S. campanulata significantly (p<0.05) reduced the MIC of tetracycline against Staph aureus. J. curcas root extract did not exhibit any antimicrobial activity against Staph. ureus, B. subtilis and P. ueruginosa but at 10 μg/ml concentration it potentiated tetracycline activity against these organisms. We hereby report the preliminary investigation of tetracycline activity potentiation by some of our local Ghanaian herbs and that these herbs may provide lead compounds that can serve as adjuvants in tetracycline formulations for the treatment of resistant bacterial infectious diseases usually encountered among HIV/AIDS patients. The results also indicate that, concomitant use of herbal products and antibiotics without prior investigation may lead to toxic side effects and should be discouraged.