Green synthesis of silver/silver oxide nanostructures using the Malva sylvestris extract prior to simultaneous distillation extraction: synthesis, phytochemical and biological analysis.

ABSTRACT

Nanotechnology and nanoscience are due to their numerous uses in medicine, engineering, and water pollution sensors and their expanding research fields. In this study, the essential oil, methanolic extract, and biosynthesized silver/silver oxide nanostructures (Ag/AgO NSs) using the aqueous extract of the plant were prepared. The phytochemical compounds of the extract and essential oil were analyzed using gas chromatography/mass spectrometry (GC/MS), respectively. The GC/MS technique identified 34 compounds in the essential oil of the plant with the major constituents including oleic acid (18.5%), palmitic acid (11.08%), phytone (6.64%), p-vinylguaiacol (6.4%), and phytol (4.23%). After the phytochemical identification, the total flavonoid and polyphenol contents of the extract was determined, too. Prodelphinidin B3 compound in the Malva sylvestris extract was analyzed and detected by high-performance liquid chromatography/ultraviolet detector (HPLC-UV), at a retention time of around 10 min. In addition, M. sylvestris extract was used for green synthesis of Ag/AgO NSs. The as-prepared NPs were characterized using X-ray diffraction (XRD), UV-visible absorption spectroscopy, scanning electron microscope equipped with energy-dispersive X-ray spectroscopy (SEM/EDS), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), and Fourier transform infrared (FT-IR) analyses. Surface plasmon resonance (SPR) absorption at λmax 320 nm in the UV-vis spectra confirms the formation of Ag/AgO NSs. The crystalline structure of Ag/AgO NSs was confirmed by XRD analysis. The nanoparticles were found to have a small size, measuring 64.16 nm, 44.33 nm, and 50 nm using the Williamson-Hall, Scherrer, and SEM/EDS methods, respectively. Besides, that spherical shape of Ag NPs with good size distribution was observed in the SEM/EDS analysis. The small size, around 50 nm, and spherical shape of Ag/AgO NSs with good size distribution were observed in the SEM/EDS analysis. Besides, the antibacterial activity of the extract was evaluated against three pathogenic bacteria, by disk diffusion method. Significant antibacterial activity was observed for the prepared extracts of M. sylvestris against the bacteria (Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa), and the results were compared with the known antibiotics such as amoxicillin, cephalexin, erythromycin, and fluconazole.