Anti-Amoebic Activity of Clitoria ternatea L. Flower Extract against Acanthamoeba culbertsoni Genotype T4

Background: Acanthamoeba culbertsoni is an opportunistic protozoan capable of causing severe infections in humans, including Acanthamoeba keratitis (AK), which predominantly affects contact lens users. Current therapeutic options remain inadequate, as no available treatment can completely eradicate the infection, primarily due to the formation of resistant cysts. Natural plant-derived compounds such as those from Clitoria ternatea L. have gained attention for their potential antimicrobial properties. Objectives: Thus, the study aimed to evaluate the in vitro anti-amoebic activity of C. ternatea L. flower aqueous extract against A. culbertsoni genotype T4, as well as to assess its cytotoxic effects on human host cells. Methods: The A. culbertsoni strain (ATCC MH791017) isolated from contact lens paraphernalia was used throughout the study. Amoebicidal, encystation and excystation assays were performed to determine the extract’s efficacy against trophozoite and cyst stages. Trophozoite viability was assessed using trypan blue exclusion with haemocytometer counting, while cytotoxicity was evaluated using the MTT assay on human keratinocyte (HaCaT) cells. Data were analysed using appropriate statistical tests, with significance set at p20 mg/mL showing significant inhibition (p5 mg/mL. Conclusion: Overall, C. ternatea flower aqueous extract demonstrated potent in vitro activity against both trophozoite and cyst stages of A. culbertsoni, likely attributable to its anthocyanin and related phytochemical constituents. These findings support further investigation to optimise efficacy, minimise cytotoxicity and validate therapeutic potential in in vivo models.