The antimicrobial activity of medicinal plants to treat sexually transmitted infections (STI's)

There are numerous ethnobotanical reports of plants used for the treatment of sexually transmitted infections, yet few studies have been undertaken to validate the use against pathogens infecting the urogenital tract. For this study, twenty plants were assessed for antimicrobial activity against STI pathogens i.e. Trichomonas vaginalis, Candida albicans, Oligella ureolytica, Ureaplasma urealyticum, Neisseria gonorrhoeae and Gardnerella vaginalis. Plant selection was based on the ethnobotanical literature [1,2,3]. Extracts were prepared by submerging the dried macerated plant material in a mixture of methanol and dichloromethane (1:1) for 24h. Antimicrobial activity was assessed using the micro-well minimum inhibitory concentration assay with specific alterations to facilitate fastidious growth of pathogens [4]. Tarchonanthus camphoratus (leaf extract) showed the most significant broad spectrum activity with MIC values ranging between 0.5–0.7mg/mL against five of the six pathogens tested. Other noteworthy activity was found for Hypoxis latifolia showing sensitivity towards T. vaginalis at 0.8mg/mL. Tarchonanthus camphoratus (leaf extract) showed notable sensitivity when tested against C. albicans (0.5mg/mL). The highest activity noted for N. gonorrhoeae was for Hypericum aethiopicum (root) at 0.3mg/mL. Polygala fruticosa and the root extract of Hypericum aethiopicum showed highest sensitivities towards G. vaginalis at 0.2mg/mL. Efficacy of the plant extracts against the pathogen O. ureolytica showed MIC values below ≤0.1mg/ml for nine plant species. The highest activity noted against U. urealyticum was for Psidium guajava at 0.8mg/mL. This in vitro evaluation validates the ethnobotanical use as an anti-infective to treat sexually transmitted diseases.

References: [1] Hutchings, A. et al. (1996) Zulu Medicinal Plants – an Inventory. University of Natal Press. Pietermaritzburg, South Africa.

[2] Watt, J.M., Breyer-Brandwijk, M.G. (1962) The Medicinal and Poisonous Plants of Southern and Eastern Africa. 2nd Edition, Livingstone, London, UK.

[3] Neuwinger, H.D.et al. (2000) African Traditional Medicine: A Dictionary of Plant Use and Applications. Medpharm. Stuttgart, Germany.

[4] NCCLS (2003) Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria. 6th Edition, USA.