Exploring the Nanoparticle Fabrication Ability of Amaranthus spinosus and Its Biological Functions

Abstract

Amaranthus spinosus is a medicinal plant with notable pharmacological properties. In the present work, silver nanoparticles (AgNPs) were synthesized using methanolic leaf extract of A. spinosus. The synthesis of AgNPs was indicated by a color change from green to brown and confirmed through UV–Vis spectroscopy, FTIR, SEM, and XRD analyses. The XRD peaks between 20° and 50° confirmed the crystalline nature of AgNPs, while SEM (1 μm scale) revealed uniformly distributed spherical nanoparticles below 100 nm. The AgNPs exhibited potent antimicrobial activity, with the highest inhibition observed against Klebsiella pneumoniae (20 mm at 100 μg), surpassing the plant extract. Antioxidant assays proved the free radical scavenging capacity of AgNPs compared with standard ascorbic acid. At 500 μg/mL, AgNPs achieved 71% DPPH scavenging, 75% hydroxyl radical scavenging, and 68% reducing power, significantly outperforming the plant extract. The in vitro anticancer property of AgNPs against HT-29 colorectal cancer cells revealed a concentration-dependent cytotoxic effect, with maximum cell death at 100 μg/mL. AO/EtBr staining confirmed apoptosis through a shift from green to orange/red fluorescence, while DAPI staining indicated nuclear condensation and fragmentation. These findings highlight A. spinosus-derived AgNPs as promising candidates for biomedical applications, offering enhanced antimicrobial, antioxidant, and anticancer properties via eco-friendly synthesis.