Comparative assessment of physicochemical and biological properties of silver nanoparticles (AgNPs) synthesized from aerial and underground parts of Arnebia benthamii

Abstract

Arnebia benthamii is a source of secondary metabolites with significant medicinal potential. This work studied the biogenic synthesis of silver nanoparticles (AgNPs) by A. benthamii root and inflorescence extracts. The novelty of this research lies in the comparative assessment of nanoparticles derived from aerial and underground plant parts, highlighting differences in physicochemical and biological properties. A 1:5 ratio of plant extract to silver nitrate (AgNO₃) solution (1 mM) was used in the formation of NPs, and they were characterized by UV-Vis spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction spectroscopy (XRD). UV-Vis analysis confirmed AgNP formation by an absorbance peak at 432 nm (root-mediated) and 436 nm (inflorescence-mediated). XRD confirmed their crystalline nature, while SEM revealed that root-derived AgNPs were irregular (40 nm) and inflorescence-derived AgNPs were spherical (23 nm). FTIR showed the part of secondary metabolites that serve as natural capping agents. For antibacterial activity, the well diffusion method was employed, where AgNPs were tested against Acinetobacter calcoaceticus and Enterobacter hormaechei subsp. xiangfangensis. Inflorescence-mediated AgNPs were found to exhibit superior antibacterial activity, likely due to smaller NP size. For antioxidant assays, these AgNPs also demonstrated enhanced 2,2-diphenyl-1-picrylhydrzyl (DPPH) of 83 % and 2,2-azino-bis(ethylbenzothiazoline-6-suphonic acid) (ABTS) of 61 % compared to root-mediated AgNPs (DPPH 80 %, ABTS 57 %). The findings suggest that A. benthamii-mediated AgNPs possess a significant potential for biological applications. Enhanced bioactivity of inflorescence-derived AgNPs highlights their promise in antimicrobial and antioxidant therapies, supporting their future use in pharmaceutical and nanotechnological advancements.