Essential Oil Components and Antitrichomonal Effects of Piper nigrum L.

Background: Trichomoniasis, caused by Trichomonas vaginalis protozoan, is the most common nonviral sexually transmitted infection (STI) worldwide. Although metronidazole and tinidazole are the only approved drugs for treatment, drug-resistant cases of infection are on the rise. The aim of this study was the evaluation of antitrichomonal potential of Piper nigrum and limonene. The phytochemical profile of P. nigrum oil was also investigated. Methods: The parasites were treated in vitro with essential oil and different extracts of P. nigrum seed and limonene using microtiter plate method. The oil of P. nigrum was also analyzed by gas chromatography-mass spectrometry and gas chromatography-flame ionization detector. Furthermore, the cytotoxicity assay of P. nigrum oil and limonene were screened on Vero cell line by MTT method. Results: The tested P. nigrum fractions were able to kill 100% of Trichomonas trophozoites at minimum lethal concentration (MLC) and reduce the trophozoite viability at sub-MLC and lower concentrations. After 48 hours exposure, the most potent fraction was the n-hexane extract with MLC of 78 µg/mL followed by the essential oil and methanol extract with MLC of 156 µg/mL, limonene (MLC=1250 µg/mL), and then, aqueous extract with MLC value of 25 mg/mL. Moreover, according to cytotoxicity assay, P. nigrum oil was less toxic to Vero cell than limonene, with a selectivity index (SI) of 13.2 and 2.04, respectively. Conclusion: This study clearly demonstrated the trichomonacidal potential of P. nigrum. Thus, P. nigrum fractions can be considered promising antiprotozoal agents and the basis for further development to discover new phytochemicals compounds.