Acaricidal efficacy of synthesized silver nanoparticles using aqueous leaf extract of Ocimum canum against Hyalomma anatolicum anatolicum and Hyalomma marginatum isaaci (Acari: Ixodidae)

The use of acaricides had limited efficacy in reducing tick infestations and is often accompanied by serious drawbacks, including the selection of acaricide resistant ticks, contamination of environment, and milk and meat products with drug residues. The present study was based on assessments of the antiparasitic activities to determine the efficacy of synthesized silver nanoparticles (AgNPs) utilizing aqueous leaf extract of Ocimum canum Sims (Labiatae) against the larvae of Hyalomma anatolicum (a.) anatolicum Koch, 1844 and Hyalomma marginatum (m.) isaaci Sharif, 1928 (Acari: Ixodidae). The synthesized AgNPs results were recorded from UV–vis spectrum, X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis. The production of the AgNPs synthesized from the leaf extract of O. canum was evaluated through UV–visible spectrophotometer in a range of wavelength from 300 to 600 nm. This revealed a peak at 426 nm in leaf extracts of O. canum, indicating the production of AgNPs. The XRD spectrum compared with the standard confirmed spectrum of silver particles formed in the present experiments were in the form of nanocrystals, as evidenced by the peaks at 2θ values of 27.71°, 32.16°, 38.08°, 46.15°, 54.70° and 57.35°. The FTIR spectra of AgNPs exhibited prominent peaks at 818, 1,045, 1,381 and 1,616 in the region 500–3,000 cm−1. The peaks correspond to the presence of a C–H vibration of the aromatic ring, stretch vibration of C–O, carbonyl groups and flavanones. SEM analyses of the synthesized AgNPs were clearly distinguishable, which measured 25–110 nm in size. It is clear that the rod and cylindrical structures have an average size of 95 nm. The EDX spectra showed the purity of the material and the complete chemical composition of the synthesized AgNPs. Parasite larvae were exposed to varying concentrations of aqueous leaf extract of O. canum and synthesized AgNPs for 24 h. The acaricidal activities of aqueous crude leaf extracts of O. canum against the larvae of H. a. anatolicum and H. m. isaaci have LC50 and LC90 values of 15.31 and 13.85 mg/L, and 62.41 and 48.86 mg/L, respectively. The efficacies of 1 mM AgNO3 solution against H. a. anatolicum and H. m. isaaci were LC50 = 12.25 and 12.17 mg/L, LC90 = 49.17 and 46.52 mg/L, respectively, and the maximum efficacy was observed in the synthesized AgNPs against H. a. anatolicum and H. m. isaaci with LC50 and LC90 values of 0.78 and 1.00 mg/L, and 1.51 and 1.68 mg/L, respectively. This method is considered as an innovative alternative approach to control parasites.