Antiparasitic activity of Loranthus europaeus Jacq. against Acanthamoeba sp.: An in vitro study

Abstract

Acanthamoeba keratitis (AK), caused by species of the genus Acanthamoeba, has become more frequently reported in recent years, particularly among contact lens users and immunocompromised individuals. Although the disease is rare, it can cause blindness; treatment resistance and limited access to care are growing concerns. This study evaluated the antiparasitic activity of Loranthus europaeus Jacq. hexane extract against trophozoite and cyst stages of Acanthamoeba sp. and identify its chemical constituents by gas chromatography-mass spectrometry (GC-MS). Serial extract concentrations (1.25, 2.5, 5 and 10 mg/mL) were applied to trophozoite and cyst suspensions for 2, 4 and 6 min and viability was assessed microscopically using trypan blue exclusion. The extract demonstrated a clear concentration and time-dependent reduction in viability (two-way analysis of variance (ANOVA), p < 0.001), reaching 0.33 ± 0.58 % at the highest concentration and longest exposure for both stages. IC₅₀ values ranged from 0.93–3.03 mg/mL across exposure times. The negative control showed no effect, whereas polyhexamethylene biguanide (PHMB, 0.02 %) reduced viability to a residual 30.67 ± 1.15 % at 6 min for both stages. The GC-MS analysis revealed a triterpenoid-rich profile 47.72 % dominated by Lup-20(29)-en-3beta-ol, acetate 42.06 % followed by sesquiterpene longipinane, germacrene D and caryophyllene. The GC-MS identifications further confirmed by retention index matching to published values. These findings point to preliminary, in vitro antiparasitic activity of L. europaeus extract against Acanthamoeba sp. an effect that may be linked to the terpenoid compounds detected in the extract. Before any translational application can be considered, further work is needed to purify the active compounds, clarify how they act and confirm the extract's safety for corneal cells.