Green synthesis of silver nanoparticles from the endophytic fungus Panax notoginseng and their antioxidant and antimicrobial activities and effects on cherry tomato preservation

Abstract

This study investigated endophytic fungi isolated from the medicinal plant Panax notoginseng. Among these, the endophytic fungus SQ3, identified as Chaetomium globosum, was capable of reducing silver ions to form metallic silver nanoparticles. The green-synthesized silver nanoparticles (AgNPs) presented a distinct surface plasmon resonance peak at 424 nm, with particle sizes between 2.92 and 31.34 nm, indicating strong antioxidant activity. In vitro assessments demonstrated that AgNPs exhibited significant antifungal activity against Phytophthora infestans, Botrytis cinerea, and Helminthosporium maydis. AgNPs produced inhibition zones measuring 17.5 mm, 15.2 mm, and 13.4 mm against Staphylococcus aureus, Escherichia coli, and Bacillus subtilis, respectively. When applied to cherry tomatoes, AgNP treatment effectively inhibited the growth of Botrytis cinerea, minimized weight loss, preserved fruit firmness and soluble solids content, slowed the reduction in titratable acidity, and prolonged storage life. Additionally, AgNPs suppressed the increase in malondialdehyde content and maintained increased superoxide dismutase activity. These findings highlight the potential of green biosynthetic silver nanoparticles as biological control agents, providing promising resources for developing innovative treatments against postharvest fungal infections in crops.