Synthesis, cytotoxicity and in vitro and in silico anthelmintic activity of eugenol and derivatives against Haemonchus contortus

This study aimed to investigate the in vitro and in silico anthelmintic activity of eugenol and derivatives against Haemonchus contortus and evaluated the cytotoxicity of these compounds. For this, acetyl eugenol (AE), benzoyl eugenol (BE), and methyl eugenol (ME) were synthesized. Eugenol, AE, BE, and, ME cytotoxicity was tested on HaCat cells and the anthelmintic effect was evaluated in the egg hatch test (EHT) and larval migration inhibition test (LMIT). Eugenol and the derivative with highest efficacy were evaluated in adult worm motility test (AWMT), followed by the assessment morphological and ultrastructural changes. In silico study was based on molecular docking with the phosphoethanolamine N-methyltransferase (PMT) enzyme. All compounds showed similar cytotoxicity profiles. Eugenol, AE, BE, and ME showed ovicidal and larvicidal effects on H. contortus. However, only the acetylation potentiated the anthelmintic effect of eugenol. In the EHT and LMIT, the EC₅₀ values of AE and eugenol were 0.19 and 0.21 mg/mL, and 0.56 and 1.35 mg/mL, respectively. In the AWMT, the EC₅₀ of eugenol and AE were both 0.11 mg/mL. The scanning and transmission electron microscopy revealed that eugenol and AE caused damage to the cuticle and internal tissues of H. contortus adults. Molecular docking suggested that eugenol and AE interact with the HcPMT. These findings indicate that acetylation may increase the anthelmintic effect of eugenol against H. contortus without significantly altering the cytotoxic potential. Therefore, in vivo assays must be realized to evaluate the toxicological safety and anthelmintic efficacy of eugenol and AE in small ruminants.