Bioactive Compounds from Tithonia diversifolia Aerial Parts Against Eggs and Infective Larvae of the Parasitic Nematode Haemonchus contortus

Small ruminant production under grazing conditions plays a crucial role in the global primary sector economy. However, these animals are highly susceptible to gastrointestinal nematodes (GINs), which significantly impact their health and welfare. Given the increasing resistance to conventional anthelmintics, there is a pressing need to explore sustainable alternatives, such as plant secondary metabolites. This study aimed to identify phenolic compounds with anthelmintic activity from <i>Tithonia diversifolia</i> aerial parts, using <i>Haemonchus contortus</i> as a biological model. Egg hatching inhibition (EHI) and larval mortality assays were used to evaluate the anthelmintic activity of a hydroalcoholic extract (HA-E), an aqueous (Aq-F) and ethyl acetate fraction (EtOAc-F), and eight bioactive subfractions (TdR1-TdR8) obtained from EtOAc-F. The identification of major compounds was performed using HPLC-PDA. The E-HA and EtOAc-F achieved 100% EHI at 40 and 4 mg/mL, respectively. The subfractions TdR2 (EC₉₀ = 0.55 mg/mL), TdR3 (EC₉₀ = 0.12 mg/mL), and TdR4 (EC₉₀ = 0.26 mg/mL) exhibited the highest ovicidal activity. In the larval mortality test, EtOAc-F showed an LC₈₅ of 56.74 mg/mL. The major identified compounds included cinnamates, hydroxycinnamic acids (e.g., caffeic acid and chlorogenic acid), gallates, flavonoids (flavones and flavanones), and coumarins. These findings support the potential of <i>T. diversifolia</i> as a promising natural source for the control of GINs in small ruminants.