Evaluating Punica granatum mediated AgNPs acaricidal activity against Rhipicephalus microplus and Sarcoptes scabiei using in vitro and in silico analyses.

Sarcoptic mange and tick infestations caused by Sarcoptes scabiei and Rhipicephalus microplus are growing veterinary and economic concerns globally. Resistance against traditional acaricides, coupled with growing concern for the environment, calls for the development of alternative control strategies. The current study aimed to develop and evaluate the acaricidal activity of silver nanoparticles (AgNPs) synthesized using a green methodology that involved the leaf extracts of Punica granatum. The AgNPs were characterized using UV-Visible spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. The synthesized AgNPs were also tested for their acaricidal activities using Adult Immersion Test (AIT), Larval Packet Test (LPT), contact bioassays, and molecular docking to determine the possible binding interactions of the bioactive metabolites with the respective target proteins. The results revealed the successful synthesis of crystalline AgNPs with a diameter of 25 to 80 nm, coupled with a strong signal for silver in the EDX analysis. The AgNPs also showed a promising bio efficacy and acaricidal activity against R. microplus and S. scabiei. In the contact bioassays, the acaricidal activity of the AgNPs extract was concentration dependent, with significant 100% mortality even at 2 mg/mL. The extract was even more active than the positive control, permethrin. In contact bioassays, prolonged exposure demonstrated an improvement in the LC₅₀ and LC₉₀ values, while the Adult Immersion Test showed a remarkable inhibition of oviposition. At a concentration of 40 mg/mL, 100% mortality rate, and 71.93% inhibition of egg-laying were observed with the AgNPs extract. This demonstrates significant suppression of tick reproduction. Computational analyses supported these findings. Structural homology of target proteins was validated using Ramachandran plots, ERRAT, and CASTp, while molecular docking showed that the most active compounds, benzene dicarboxylic acid and 3-amino-N-(pyridin-4-yl) propanamide had the highest binding affinities to the aspartic proteases of S. scabiei and R. microplus, thus aligning with the observed bioactivity. In silico studies underscored novel phytocompounds with strong inhibitory potential as the extract and the as-synthesized AgNPs exhibited potent acaricidal activity, underscoring them as promising candidates to replace synthetic acaricides.