Green synthesis of silver nanoparticles from Artemisia afra and Artemisia annua leaf extracts: Enhanced in vitro anthelmintic activity against Haemonchus contortus

Abstract

Rising anthelmintic resistance in Haemonchus contortus and other gastrointestinal nematodes poses a critical challenge to livestock parasite management, underscoring the urgent need for novel therapeutic agents. This study evaluated the in vitro anthelmintic potential of green-synthesized silver nanoparticles (AgNPs) derived from Artemisia afra and Artemisia annua leaf extracts against adult worms. Aqueous leaf extracts were utilized to biosynthesize AgNPs by optimizing reaction parameters, including extract-to-silver nitrate ratio, concentration, pH, and incubation time. Phytochemical characterization identified alkaloids, coumarins, tannins, polyphenols, and saponins in both species, with A. afra demonstrating markedly higher total phenolic (282 mg GAE/g) and flavonoid (3655.56 mg QE/g) contents than A. annua. UV-Vis spectroscopy confirmed nanoparticle synthesis, exhibiting characteristic surface plasmon resonance peaks at 435 nm (A. afra-AgNPs) and 456 nm (A. annua-AgNPs). Anthelmintic efficacy was assessed using the Adult Worm Motility Assay across a concentration gradient (3-48 microg/mL) over 24 hours. Both AgNP formulations displayed dose-dependent inhibition of motility. Notably, A. afra-AgNPs exhibited superior potency, achieving lower IC50; values at 12 hours compared to A. annua-AgNPs and the commercial anthelmintic levamisole. At 48 microg/mL (12 hours), A. afra-AgNPs demonstrated significantly greater motility inhibition than A. annua-AgNPs, while surpassing levamisole at 12 microg/mL (18 hours). These findings highlight green-synthesized AgNPs from Artemisia species, particularly A. afra, as potent, eco-friendly nano-anthelmintic candidates, offering a sustainable approach to mitigate drug-resistant nematode infections in livestock.