In vitro evaluation of the anthelmintic activity of citrus flavonoids against free-living and parasitic nematodes.

Helminth infections remain a significant global health and economic burden, and the growing emergence of resistance to frontline anthelmintic drugs such as albendazole and ivermectin underscores the urgent need for novel therapeutic strategies. Flavonoids, a diverse group of plant-derived polyphenolic compounds, have gained attention for their broad-spectrum biological activities, including potential antiparasitic properties. This study aimed to investigate the anthelmintic potential of orange-derived flavonoids using two complementary models: the free-living nematode Caenorhabditis elegans (wild-type, albendazole-resistant, and ivermectin-resistant strains) and the muscle-stage larvae of Trichinella spiralis as a representative parasitic nematode. Among the five flavonoids tested, quercetin exhibited the strongest anthelmintic activity across all C. elegans strains and against T. spiralis, while demonstrating minimal cytotoxicity in human cell lines, indicating a favorable safety profile. To investigate its potential mode of action, electron microscopy was employed to assess morphological changes, while a mass spectrometry-based metabolomics approach was used to examine molecular mechanisms in T. spiralis treated with quercetin. The results showed that quercetin did not induce detectable morphological alterations but significantly disrupted multiple key metabolic pathways, particularly those associated with energy production, lipid metabolism, and mitochondrial function, indicating a systemic metabolic disturbance. These findings offer new insights into the metabolic effects of orange-derived flavonoids and underscore quercetin as a promising lead candidate for anthelmintic development.