Abstract
Cyclachaena xanthiifolia is a phytochemically rich invasive weed with documented allelopathic properties, making it a candidate source of bioactive compounds with potential medicinal applications. This study investigated the anthelmintic activity of a crude aqueous-ethanolic extract of C. xanthiifolia (CxEt), prepared from equal proportions of leaves and seeds, against the trematode Opisthorchis felineus in vitro. The effects of CxEt on the motility and mortality of newly excysted metacercariae (NEMs) and adult flukes (maritae) of O. felineus were assessed across a concentration range of 0.1-1000.0 µg/mL. Secondary metabolite content was quantified, antiradical activity was determined by the DPPH assay, and cytotoxicity was evaluated by the MTT assay using cultured HFF10 cells. CxEt demonstrated strong anthelmintic activity: half-maximal inhibitory concentrations (IC50) for motility reduction were 13.4 µg/mL for NEMs and 10.9 µg/mL for maritae. Complete lethality at 24 h was achieved at 800 µg/mL for NEMs and 1000 µg/mL for maritae, with lethal effects observed at lower concentrations (400-600 µg/mL) over 3-4 days of continued observation. Cytotoxicity assessment yielded an IC50 of 168 µg/mL after 72 h of exposure, indicating a favorable selectivity profile relative to the anthelmintic IC50 values. CxEt also demonstrated moderate antiradical activity (DPPH IC50 580 µg/mL). Elevated concentrations of triterpene saponins (4.03%) and phenolic compounds, including tannins and hydroxycinnamic acids (8.20 mg GAE/g) were identified as likely contributors to the observed bioactivity. These findings establish C. xanthiifolia as a promising source of opisthorchicidal compounds and support its further investigation as a plant-derived anthelmintic agent.