Phytochemical profiling-guided green synthesis and characterisation of silver nanoparticles using Catunaregam spinosa for biological applications.

In this study, an aqueous extract of Catunaregam spinosa (C. spinosa) leaves and roots was used to produce silver nanoparticles (AgNPs) in an environmentally friendly manner. Visual observation of the color change in the reacting solution and measurement of surface plasmon resonance by Ultraviolet-visible (UV-vis) spectroscopy at 414 nm for leaf-assisted silver nanoparticles (L-AgNPs) and 416 nm for root-assisted silver nanoparticles (R-AgNPs) were used to confirm nanoparticle (NPs) synthesis. Furthermore, NPs were examined by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), and Energy-dispersive X-ray analysis (EDX). FTIR spectra confirmed the utilization of various phytoconstituents as capping, reducing, and stabilizing agents during NPs formation. The average particle size of L-AgNPs in XRD was 11.57 ± 0.35 nm, while the average particle size of R-AgNPs was 10.05 ± 3.17 nm. The diameters of L-AgNPs (38.79 ± 0.62 nm) and R-AgNPs (39.93 ± 0.84 nm) were estimated using FE-SEM. The EDX investigation revealed that both AgNPs exhibited peaks at about 3 keV, as well as peaks for other elements such as O, N, Zn, C, and Cl. L-AgNPs showed substantial antioxidant activity, as determined by the enzyme marker 2,2-diphenyl-1-picrylhydrazyl (DPPH) with IC50 106.10 ± 0.00 µg/mL. Furthermore, NPs exhibited strong antibacterial activity against human pathogenic bacterial strains. The toxicity of AgNPs was tested against brine shrimp nauplii, in which L-AgNPs (LC50 = 12.31 ± 11.93 µg/mL) were more toxic than R-AgNPs, indicating their potential for several biomedical applications.