Green synthesis and biological activities of gold nanoparticles functionalized with Salix alba

This study reports a facile and reproducible green extracellular synthetic route of highly stable gold nanoparticles. The aqueous gold ions when exposed to Salix alba L. leaves extract were bioreduced and resulted in the biosynthesis of gold nanoparticles (Au-WAs). The nanoparticles were characterized by UV–Visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Their stability was evaluated against varying volumes of pH and sodium chloride as well as at elevated temperature along with enzymes inhibition, antibacterial, antifungal, anti-nociceptive, muscle relaxant and sedative activities. The UV–Vis spectra of the gold nanoparticles gave surface plasmon resonance at 540nm while the AFM and SEM nanoparticles analyses revealed the particle size of 63nm and 50–80nm respectively. FTIR spectra confirmed the involvement of amines, amide and aromatic groups in capping and reduction of the gold nanoparticles. Au-WAs showed remarkable stability in different volumes of salt and various pH solutions however, Au-WAs were relatively unstable at elevated temperature. Au-WAs possessed good antifungal activity and showed significant antinociceptive and muscle relaxant properties. These results revealed that the leaves extract of S. alba is a very good bio-reductant for the synthesis of gold nanoparticles that have potential for various biomedical and pharmaceutical applications.