Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 19 1 2024 02 28 18 27 Masoumeh Moradi Department of Medical Parasitology and Mycology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran Dara Dastan 1. Medicinal Plants and Natural Products Research Center, Hamadan University of Medical Sciences, Hamadan, Iran 2. Department of Pharmacognosy and Pharmaceutical Biotechnology, School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran Mohammad Fallah Department of Medical Parasitology and Mycology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran Manizhe Kashi Nahanji Department of Medical Parasitology and Mycology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran Mohammad Matini Department of Medical Parasitology and Mycology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran 2023 04 13 2024 01 06 Background: Trichomoniasis is one of the most common sexually transmitted infections worldwide. The growing concern of drug resistance of this infection has cautioned the need for new drug development. We evaluated the potential antiproliferative and apoptotic effect of α-pinene and tannic acid (TA) on Trichomonas vaginalis cells. In addition, the cytotoxicity of agents on Vero cells was investigated. Methods:  Trichomonas cells were axenically cultured in TYI-S-33 medium. In vitro antiproliferative activity of α-pinene, TA, and metronidazole was investigated against Trichomonas cells. The assays were carried out in triplicate using microtiter plate and trypan blue staining method. Annexin V/PI staining with flow cytometry was used to evaluate apoptosis induction. In addition, the cytotoxic effect was measured by MTT assay. Results: α-Pinene and TA exhibited significant inhibition of the Trichomonas cells and the lowest IC50 values were 22.9 µg/ml and 140 µg/ml at 48 hours’ incubation, respectively. The CC50 was found at 116 μg/ml for α-pinene and 473 μg/ml for TA, after 48 hours of treatment. The flow cytometry study demonstrated that the natural compounds induced apoptosis in Trichomonas cells. After 24 hours of treatment, the induction of apoptosis was 5.2% - 36.6% at concentrations of 3.9 - 62.5 μg/ml for α-pinene and TA induced-apoptosis was 6.1% - 53.8% at concentrations of 125-2000 μg/ml. Conclusion: Although the results show the antiproliferative and apoptotic effect of α-pinene and TA on Trichomonas cells, in vivo studies are needed to further clarify the effects of these compounds. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/3920 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/3920/1337