Antimicrobial and antioxidant activity of AgNPs stabilized with Calendula officinalis flower extract

Abstract

The present research is devoted to optimizing the green synthesis technology of silver nanoparticles (AgNP) with antibacterial properties for further external use. Standardized marigold flowers extract was utilized as reducing and stabilizing agent, which has significantly richer composition of phytochemical groups compared to its aqueous extracts. A comparative analysis of the physicochemical properties and sedimentation stability of AgNPs obtained by exposure of the reaction mixture to: UV radiation, microwave radiation and high temperature using UV–Vis spectrophotometry and Zeta potential analysis were carried out. pH effect of the reaction mixture on size distribution of AgNPs was evaluated. A good stability of AgNPs to aggregation was observed for samples generated under ultraviolet irradiation with continuous stirring. The particle size distribution obtained by UV irradiation with an average size of 80 nm and PDI 0.26. The storage of AgNPs at 4 °C resulted in some aggregation of small size AgNPs that led to the increase the absorbance at 430 nm. Thus, after one month of storage there was no following increase of the absorbance and there was non-significant aggregation over 3 months’ study. Antibacterial activity of AgNPs against S. aureus and E. coli was estimated with and without light irradiation (445 and 635 nm, 14 W). Additionally, the antioxidant activity of the plant extract and the AgNPs stabilized by the extract was estimated.