Partial purification and characterization of Trichomonas vaginalis DNA topoisomerase II.

DNA topoisomerases regulate conformational changes in DNA topology by catalyzing the breakage and rejoining of DNA strands during the cell cycle. These processes are essential for the multiplication of cells, and inhibition of these reactions stops cell division and cell growth. Drug resistance to Trichomonas vaginalis, a common sexually transmitted protozoan parasite, is increasing worldwide, and DNA topoisomerase II may provide a new target for anti-trichomonal drug development. In this study, T. vaginalis DNA topoisomerase II was partially purified from a large scale axenic culture using fast protein liquid chromatography with a yield of 0.16% and 17-fold purification. The partially purified enzyme was strictly dependent on ATP and Mg2+ with optimal concentration of 1 and 10 mM respectively for relaxation activity. T. vaginalis DNA topoisomerase II activity was inhibited by m-amsacrine (m-AMSA) and ofloxacin at minimum inhibitory concentration (MIC) of 250 microM. At this concentration, ciprofloxacin showed incomplete inhibition whereas metronidazole was inactive. DW6, a DNA quadruplex binder, was the most active compound with MIC of 62.5 microM, suggesting the potential for development of such compounds as selective anti-trichomonal drugs in the future.

Inhibitory effects of Thai plants beta-glycosides on Trichomonas vaginalis.

Trichomoniasis is now an important health problem in developing countries. Although metronidazole has so far been widely used to treat this disease, the prevalence of metronidazole-resistant protozoa and unpleasant adverse effects have been found. In this study, natural products purified from Thai plants were, therefore, investigated for their effectiveness against Trichomonas vaginalis. The minimal inhibitory concentrations for all beta-glycosides against Trichomonas vaginalis at 24 h were in a range of 6.25-12.5 microM. In addition, torvoside A and H were found to be more potent than their corresponding aglycones, deglucosylated torvoside A and H, while other beta-glycosides were generally as active as their corresponding aglycones. The cytotoxicity of these compounds was also determined. Except for dalcochinin, none of the tested compounds showed cytotoxicity against Vero and cancer cell lines (KB and MCF-7), having IC(50) values greater than 50 microg/ml. In conclusion, beta-glycosides and several aglycones showed selective inhibition against Trichomonas vaginalis without harmful effect to mammalian cells.