Discussion
The liver fluke species, Fasciola gigantica and Fasciola hepatica, responsible for fasciolosis, also exhibit zoonotic potential. The emergence of drug resistance against the commonly available anthelmintics including Triclabendazole necessitates the search for alternative measures. Two active ingredients, thymoquinone and curcumin,known for their therapeutic efficacy in a number of ailments, were in silico screened and tested for their in vitro anthelmintic effect on adult F. gigantica flukes.
Worms were treated with different concentrations of thymoquinone and curcumin separately for 3h along with controls. Post treatment alterations in CathepsinL gene expression, various antioxidant enzymes and surface topography were investigated. The molecular interactions of curcumin with cathepsinL of
F. gigantica in silico revealed stronger interactions with curcumin as compared to thymoquinone, while CatL expression was significantly inhibited in thymoquinone treated worms. Following initial stimulation of antioxidant enzymes at lower concentrations, both thymoquinone and curcumin at 60µM concentration significantly (p<0.05) inhibited GST and SOD activities and the level of reduced glutathione (GSH) also declined. Further, protein carbonylation in flukes increased differentially in response to the treatment with both the compounds in a concentration dependent manner. Scanning electron microscopy revealed significant damage to the tegumental surface structures. It is concluded that both the compounds understudy will decrease the detoxification ability of
F. gigantica by inhibiting the key antioxidant enzymes, while inhibition of CatL will significantly affect their virulence potential establishing both thymoquinone and curcumin as a promising candidates for future studies.
