In Vitro Anthelmintic Activity of Isatis tinctoria Extracts against Ewes' Gastrointestinal Nematodes (GINs), a Possible Application for Animal Welfare

Sheep gastrointestinal nematode (GIN) infestation represents a limiting factor for sheep farming and milk production in Italy. The development of anthelmintic resistance to conventionally used drugs suggests the path towards the use of natural remedies as a possible alternative. The purpose of this study is to evaluate the in vitro anthelmintic efficacy of the hydroalcoholic extracts of basal leaves (It-BL), cauline leaves (It-CL) and flowers (It-F) of Isatis tinctoria (Brassicaceae), a spontaneous Sicilian species renowned as an important source of bioactive compounds. The dry extracts of the different parts of the plant were tested using the egg hatch test (EHT) in vitro to verify the efficacy against ovine GIN at different concentrations (1.00, 0.5, 0.25, 0.125 mg/mL). Thiabendazole and deionized water were used as positive and negative controls, respectively. The results obtained from EHT indicated that all the I. tinctoria extracts were highly effective (p < 0.0001) in inhibiting egg hatching within 48 h of exposure. The in vitro inhibitory effect was never less than 84% in all doses tested, and it was only slightly lower than the standard drug thiabendazole (95.6%). The current study documents the anthelmintic activity of I. tinctoria against sheep's GIN, suggesting its application as alternative natural method to limit the use of antiparasitic drugs.