Background: Sexually transmitted diseases (STD's) have a major impact on sexual and reproductive health worldwide. Each year, the World Health Organization (WHO) estimates 448 million new cases of curable STD's are diagnosed. The emergence of drug resistance in STD related microorganisms and potential side effects demand the discovery of newer drugs. The exploration of newer anti-microbial substances from natural sources may serve as promising alternatives. In this study, twelve medicinal plant species used traditionally in the treatment of STD's are investigated in this regard.
Methods: Ethanol plant extracts and three flavonoids were evaluated for their antimicrobial properties against one fungi and three bacteria, through the micro-dilution assay. To determine the anti-inflammatory activities of the extracts and compounds, the inhibitory effect was measured on the pro-inflammatory enzyme lipoxygenase, 15-LOX. Extracts were further evaluated for their inhibitory effect on the supercoiling activity of bacterial DNA gyrase by using the DNA gyrase kit. The extracts and compounds were lastly investigated for their anti-HIV activities against recombinant HIV-1 enzyme using non-radioactive HIV-RT colorimetric assay.
Results: Acacia karroo and Rhoicissus tridentata extracts showed good antimicrobial activity with MIC values ranging between 0.4 and 3.1 mg/ml. Extracts of Jasminum fluminense, Solanum tomentosum and flavonoid 2 and 3 had good anti-inflammatory activity with IC50 less than the positive control quercetin (IC50 = 48.86 ug/ml). Extracts of Diospyros mespiliformis, Peltophorum africanum, Rhoicissus tridentata and flavonoids 1 and 2 showed the best inhibitory activity against the bacterial DNA gyrase. A. karroo and flavonoid 3 exhibited moderate HIV RT inhibition activity of 66.8 and 63.7 % respectively. R. tridentata and Terminalia sericea had the best RT inhibition activity (75.7 and 100 %) compared to the positive control doxorubicin (96.5%) at 100 ug/ml concentration.
Conclusion: The observed activities may lead to new multi-target drugs against sexually transmitted diseases.