Exploring novel pyrazole-nitroimidazole hybrids: Synthesis and antiprotozoal activity against the human pathogen...

Trichomoniasis, a prevalent sexually transmitted infection (STI) caused by the protozoan Trichomonas vaginalis, has gained increased significance globally. Its relevance has grown in recent years due to its association with a heightened risk of acquiring and transmitting the human immunodeficiency virus (HIV) and other STIs. In addition, many publications have revealed a potential link between trichomoniasis and certain cancers. Metronidazole (MTZ), a nitroimidazole compound developed over 50 years ago, remains the first-choice drug for treatment. However, reports of genotoxicity and side effects underscore the necessity for new compounds to address this pressing global health concern. In this study, we synthesized ten pyrazole-nitroimidazoles 1(a-j) and 4-nitro-1-(hydroxyethyl)-1H-imidazole 2, an analog of metronidazole (MTZ), and assessed their trichomonacidal and cytotoxic effects. All compounds 1(a-j) and 2 exhibited IC₅₀ values ≤ 20 μM and ≤ 41 μM, after 24 h and 48 h, respectively. Compounds 1d (IC₅₀ 5.3 μM), 1e (IC₅₀ 4.8 μM), and 1i (IC₅₀ 5.2 μM) exhibited potencies equivalent to MTZ (IC₅₀ 4.9 μM), the reference drug, after 24 h. Notably, compound 1i showed high anti-trichomonas activity after 24 h (IC₅₀ 5.2 μM) and 48 h (IC₅₀ 2.1 μM). Additionally, all compounds demonstrated either non-cytotoxic to HeLa cells (CC₅₀ > 100 μM) or low cytotoxicity (CC₅₀ between 69 and 100 μM). These findings suggest that pyrazole-nitroimidazole derivatives represent a promising heterocyclic system, serving as a potential lead for further optimization in trichomoniasis chemotherapy.