Anthelmintic Activity of Protocatechuic Acid Against Ivermectin-Susceptible and Resistant Haemonchus contortus Strains

The frequent and indiscriminate use of all classes of synthetic anthelmintics to deworm small ruminants has decreased their effectiveness in a worldwide problem of anthelmintic resistance. Using active plant metabolites with anthelmintic properties has become a suggested alternative to control parasitic helminths. The present study investigated the ovicidal and larvicidal activity of a fraction (CnF4) containing protocatechuic acid (3,4-dihydroxybenzoic acid) from <i>Chamaecrista nictitans</i> (Fabaceae) and a commercial standard of protocatechuic acid against strains of the parasitic nematode <i>Haemonchus contortus</i> susceptible (HcIVM-S) and resistant (HcIVM-R) to ivermectin, using egg hatch inhibition (EHI) and L3 larval mortality assays. The CnF4 fraction showed an EHI greater than 90% at 0.8 mg/mL against HcIVM-S and an EHI = 88.39% at 1.6 mg/mL against HcIVM-R. The commercial standard of protocatechuic acid displayed an EHI of 97.49% at 0.25 mg/mL against HcIVM-S and an EHI greater than 98% at 0.5 mg/mL. In the larval mortality assays, protocatechuic acid caused 72.4% larval mortality of HcIVM-S at 8 mg/mL and 53.2% mortality of HcIVM-R at 16 mg/mL. These results indicate that protocatechuic acid was more effective in inhibiting egg hatching and causing larval mortality against HcIVM-S compared to HcIVM-R.