Trichomonicidal activity of a new anthraquinone isolated from the roots of Morinda panamensis Seem

Trichomoniasis, caused by the protozoan parasite Trichomonas vaginalis, is the most common nonviral sexually transmitted infection worldwide. Although drug treatment is available, unpleasant side effects and increased resistance to the nitroimidazole family have been documented. Hence, there is a need for the identification of new and safe therapeutic agents against T. vaginalis. Antimicrobial activity of anthraquinone compounds has been reported by a number of authors. The genus Morinda is well known for the diversity of anthraquinones with numerous biological activities. A new anthraquinone, lucidin-ω-isopropyl ether, was isolated from the roots of Morinda panamensis Seem. The structure of the compound was determined by ¹ H and ¹³ C Nuclear Magnetic Resonance (NMR) analyses, in addition to comparison with literature reports. Using in vitro susceptibility assay, the half inhibitory concentration (IC₅₀ ) of lucidin-ω-isopropyl ether for T. vaginalis (1.32 μg/mL) was found similar to that of metronidazole concentration tested (6 μM = 1.03 μg/mL). In addition, this anthraquinone was capable of inhibiting the parasite's ability to kill HeLa cells and decreased proteolytic activity of the proteinase TvMP50 from T. vaginalis. This was associated with the decreased expression of the mp50 gene. These results demonstrate the trichomonicidal potential by lucidin-ω-isopropyl ether. Further action-mode studies are necessary to elucidate the antiparasitic mechanism of this new anthraquinone to develop a more potent antitrichomonal agent.