Biosynthesis of Silver Nanoparticles in Prunella vulgaris L. Extracts and Evaluation of the Bioactivity of Nanoformulations with Importance in Plant Protection

The evaluation of local natural resources and their sustainable use as alternatives for allopathic medicines or phytosanitary treatments based on chemical syntheses, is a priority of research worldwide. The aim of this research was to obtain Prunella vulgaris L. extracts through modern, ecofriendly methods, to evaluate their ability to biosynthesize silver nanoparticles (AgNPs), as well as the physicochemical characterization of AgNPs to determine the polyphenol content, antioxidant and antimicrobial activity as well as phytotoxicity of the resulting nanoformulations, through in vitro tests. Microscopic analysis of the extracts showed the spherical shape of AgNPs, especially in the biosynthesized samples from the microwave extracts. The sizes of the nanoparticles ranged between 8.64 and 13.84 nm. Microwave-assisted extraction favored the procurement of crude extracts from P. vulgaris herba with a high content of polyphenols (77.98 mg GAE/g dw−1) and a correlated antioxidant activity. Rosmarinic acid was identified in all analyzed samples (61.8287–1.0031 mg/L). The extracts obtained using microwaves, in which the nanoparticles were also biosynthesized using microwaves, had the best antifungal activity against Fusarium oxysporum MUCL 791. The combination of antifungal properties with those of seedling growth stimulation are of major importance in plant culture, with the early stages of their life cycle requiring constant attention.