Phytochemical investigation and phytosynthesis of eco-friendly stable bioactive gold and silver nanoparticles using petal extract of saffron (Crocus sativus L.) and study of their antimicrobial activities

Abstract

In this study, aqueous extract of saffron petal was used to synthesize gold nanoparticles (GNPs) and silver nanoparticles (SNPs). The antioxidant activity, phenol, flavonoids, anthocyanin, and carotenoids were measured in methanol, ethanol, and water extracts to assess the reducing potential. After extracting, for the phytosynthesis of GNPs and SNPs, the extract was added to the solutions of gold (III) and silver nitrate at a concentration of 1 mM. The effective parameters for the synthesis, i.e., pH of reaction solution, extract volume, metal ion concentration, and reaction time, were optimized by UV–Vis spectroscopy technique, and the nanoparticles (NPs) were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Antimicrobial activities of extracts, GNPs, and SNPs were investigated against Staphylococcus aureus, Bacillus cereus, Escherichia coli, Aspergillus, and Candida albicans. The results shown that the aqueous extract although exhibiting less antioxidant activity than other extracts, but have a high potential for reducing and stabilizing of metal ions to synthesis NPs. In addition, the NPs had a uniform spherical shape with an average of 17–22 nm for GNPs and 10–14 nm for SNPs. These sizes are useful for inhibiting many bacteria, so that according to the results of this study, phytosynthesized nanoparticles could inhibit all bacteria that had used, and this inhibitory effect on SNPs was greater than GNPs. According to the results of this study, plants are high potential for the synthesis of metal NPs, which can be used as an antibiotic to inhibit many pathogenic bacteria and fungi.