Green Synthesis and Bioactivity Evaluation of Silver Nanoparticles from Stevia rebaudiana and the Endophyte Aspergillus versicolor

This study demonstrates the green synthesis of silver nanoparticles (AgNPs) using Stevia rebaudiana (Bertoni) Bertoni leaf extract and endophytic fungus Aspergillus versicolor strain PSFNRO-2. The synthesized nanoparticles exhibited favorable physicochemical properties, including nanoscale dimensions and crystalline structure, as confirmed by spectroscopic and microscopic analysis. Comprehensive bioactivity evaluations revealed that the endophyte-derived AgNPs possessed superior antimicrobial, antioxidant, antidiabetic, and cytotoxic properties compared to plant extract-synthesized nanoparticles. Notably, the endophyte-mediated AgNPs demonstrated significantly enhanced antibacterial efficacy against Pseudomonas aeruginosa and exhibited strong inhibitory effects on α-amylase activity, indicating potential antidiabetic properties. Phytochemical screening identified a diverse array of bioactive compounds, including flavonoids, phenolic acids, tannins, terpenoids, and steviol glycosides, which functioned synergistically as reducing/capping agents, as well as direct antimicrobial contributors. These phytochemicals work in concert with silver ions to induce oxidative stress, disrupt microbial membranes, and inhibit the growth of pathogens through multiple mechanisms. The findings highlight endophyte-mediated green synthesis as a promising biotechnological approach for producing potent therapeutic nanoparticles. This work represents the first comprehensive evaluation of AgNPs biosynthesized using Aspergillus versicolor PSFNRO-2 from Stevia rebaudiana (Bertoni) Bertoni, demonstrating their potential as sustainable alternatives to conventional antimicrobial and pharmaceutical agents.