Biogenic Synthesis of Silver Nanoparticles Using Rhazya stricta Extracts and Evaluation of Its Biological Activities

Abstract

Rhazya stricta is a well-known medicinal plant and source of numerous potential secondary metabolites including steroids, alkaloids, and tannins. R. stricta possesses multimedical applications and used for curing of various diseases such as inflammation, diabetes, sore throat, infectious, helminthiasis, arthritis, and cancer. The current investigation deals with synthesizing AgNPs using aqueous and ethanol extracts of R. stricta. The synthesized R. stricta-AgNPs were characterized through UV-visible, Fourier transform infrared (FTIR), and atomic force microscopy (AFM) methods. The UV-visible analysis exhibited a characteristic absorption ${\lambda }_{\max }$ at 475 nm in R. stricta ethanol AgNPs while this peak was absent in R. stricta aqueous crude extract. The thermal stability of R. stricta-AgNPs demonstrated that by increasing the reduction time and temperature, the absorption of AgNPs also increased, leading to more stable NPs formation. The FTIR spectra showed a broad peak at 450-550 cm-1 that confirmed the occurrence of AgNPs of R. stricta. The AFM study of the synthesized AgNPs revealed the spherical shape and size ranging from 30 nm to 90 nm. In antioxidant and antibacterial study, the R. stricta-AgNPs exhibited good antioxidant activity (87.94% and 88.37%) than the ethanol crude extract (50.00% and 56.81%) at 100 μg/mL using DPPH assay. Maximum antibacterial activity was recorded against Gram-positive bacteria (Staphylococcus aureus), which was 15 and 0 mm, while against Gram-negative bacteria (Klebsiella pneumonia) was found to be 16 and 14 mm, respectively, whereas against Bacillus subtills, a poor activity was recorded as 14 for extract and 0 mm for AgNPs, respectively. In the acetic acid-induced writhing model, the percent effect of extract (100 mg/kg) and AgNPs (15 mg/kg) was 79.98 and 83.23, respectively. The maximum muscle coordination effect of extracts in the inclined plan and traction test was 44% and 38% at higher doses. A mild sedative effect was also recorded against extract and AgNPs. The significant ( $p<0.05$ ) effect of extract was noted at 100 mg/kg while AgNPs was more significant ( $p<0.01$ ) at the tested dose of 15 mg/kg. These findings have concluded that R. stricta-AgNPs is an effective bioreductant of AgNPs synthesis and exhibit several applications in distinctive biomedical and pharmaceutical industries.