Green Biosynthesis of Silver Nanoparticles Using Glycyrrhiza glabra L. Extract and Evaluation of their Selective Antimicrobial Activity

The aim of present study is to determine the content of some phytochemicals in stem and leaf extracts of the medicinal plant of Glycyrrhiza glabra and design a green method for biosynthesis of silver nanoparticles by these extracts as stabilizers and bioreducers. The properties of the synthesized silver nanoparticles (AgNPs) were monitored by using Ultraviolet-Visible absorption spectroscopy (UV-Vis) and fully characterized by scaning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The effect of different parameters including concentration of the extracts and silver nitrate salt, reaction time, temperature and thier intraction on bio-reduction process were also disscused. In addition, antibacterial and antifungul activities of the extracts and the synthesized AgNPs were assessed against 4 positive and negative bacteria by disc diffusion method and also the fungus Fusarium oxysporum. Results indicated that the bio-reduction process was relatively fast and the resulting nanoparticles were nearly spherical in their shapes with the size range of 5-45 nm. The best conditions for biosynthesis were achieved in 1-3 mmol AgNO3, 60 °C temperature and 4 h reaction time. All the extracts and their corresponding nanoparticles had good inhibition activities against bacteria tested. However, the extracts showed more inhibition activity against Gram positive bacteria, while the synthesized AgNPs were more active against Gram negative bacteria. This is the first report on the green synthesis of AgNPs using G. glabra extract followed by an estimation of their biological activities may open new insight in the applications of these nanoparticles for various purposes.