Antioxidant and antifungal activities of green synthesized silver nano-particles in comparison with essential oil, and extracts of O. vulgare leaves

Aromatic plant essential oils (EO) and their derivatives are promising, eco-friendly alternatives for fungal disease management in plants due to their low toxicity and environmental compatibility. However, practical applications are often limited by challenges such as high volatility, poor water solubility, and inefficient dispersion. To address these limitations, we developed an innovative approach to enhance the stability and antimicrobial efficacy of Origanum vulgare extracts through the green synthesis of silver nanoparticles (AgNPs). The synthesized AgNPs were characterized using UV-Vis spectroscopy and scanning electron microscopy (SEM). UV-Vis analysis revealed characteristic surface plasmon resonance (SPR) peaks at 445 nm (aqueous AgNPs) and 435nm (methanolic AgNPs), confirming nanoparticle formation. The aqueous extract exhibited the highest total phenolic content (50.3 ± 1 mg gallic acid/g), while methanolic AgNPs demonstrated the strongest antioxidant activity, scavenging 89.7 ± 0.2% of DPPH radicals with an IC₅₀ of 19.6 ± 0.3 µg/cm³. The antifungal activity of O. vulgare essential oil, AgNPs, and crude extracts was evaluated against Aspergillus niger, Botrytis cinerea, and Penicillium expansum. GC-MS analysis identified carvacrol (56.53%), thymol (21.18%), p-cymene (6.22%), and γ-terpinene (5.67%) as the major EO constituents. We are the first to report the green synthesis of AgNPs using O. vulgare extracts with comparative evaluation against crude extracts and essential oils for enhanced antifungal application. This study presents a significant advancement in fungal control strategies by demonstrating that AgNPs synthesized from O. vulgare extracts not only retain the high antifungal and antioxidant properties of the essential oil but also overcome its limitations through improved stability, water solubility, and dispersion. The findings suggest that AgNPs synthesized from O. vulgare are a more effective and sustainable alternative to conventional essential oils for combating fungal pathogens in agricultural and post-harvest applications.