Green synthesis of silver nanoparticles from Stachys byzantina K. Koch: characterization, antioxidant, antibacterial, and cytotoxic activity

Abstract

In the present study, silver nanoparticles were synthesized by aqueous extract of Stachys byzantina K. Koch and characterized by various analytical methods. The formation of AgNPs was confirmed by UV–Visible spectroscopy at 441.75 nm. The XRD study affirmed the crystalline structure of AgNPs. The value of zeta potential was −43.9 mV that showed the stability of nanoparticles. The TEM images revealed well-distributed nanoparticles with spherical shapes and an average size of 17 nm. FT-IR spectra depicted the presence of different functional groups such as hydroxyl and carbonyl substituents of biomolecules. These groups acted as reducing and capping agents which led to the stability and dispersion of AgNPs. The quantitative phytochemical investigations revealed the presence of phenolic compounds and flavonoids in the aqueous extract and on the surface of AgNPs. Also, they indicated strong antioxidant activity (IC50=48.29 µg.ml−1) in the DPPH assay. The AgNPs had the best antibacterial effects against Escherichia coli and Pseudomonas aeruginosa (MIC = 12.5 µg.ml−1). The AgNPs showed remarkable cytotoxic activities against A431, B-CPAP, and HepG2 (IC50=8.16 ± 0.99, 11.39 ± 3.24, and 11.85 ± 0.33 µg.ml−1, respectively). Also, these three cell lines revealed the best selectivity index (≥3) which demonstrated that they are significantly more toxic to cancerous cell lines than the healthy one.