In this paper we report the Laurus nobilis L. (Laurel) leaf aqueous extract mediated synthesis of gold nanoparticles (AuNPs) at room temperature and its antimicrobial activity against drugresistant microbial isolates is evaluated. The prepared AuNPs were characterized using Uv–visible spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), Fouriertransform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). The impact of extract concentration, extract pH, and contact time on the size and shape of synthesized AuNPs is studied. Only 45 min were required for the complete reduction and capping of Au3+ into gold nanoparticles (Au0) at room temperature. TEM analysis along with DLS measurements of the gold nanoparticles revealed a size ranging from 14 to 39 nm with average size of 21.9 nm. X-ray diffraction (XRD) study confirmed crystalline nature of the synthesized particles. FTIR of the purified and lyophilized gold nanoparticles revealed the surface adsorption of biomolecules during synthesis of AuNPs confirming the role of Laurel extract in capping and stabilization of AuNPs.The antimicrobial potential of the synthesized AuNPs were compared with that of aqueous laurel leaf extract by standard well diffusion method. The AuNPs significantly inhibited bacterial growth against multidrug resistant Gram Positive bacteria (Bacillus subtillus ATCC 6633, Staphylococcus aureus ATCC 25923), Gram negative bacteria (E. Coli ATCC 25922, Salmonella typhimurium ATCC 14028 and Pseudomonas Aeruginosa ATCC 27858) and Fungi (Candida albicans ATCC 10231). The study revealed that the aqueous laurel leaf extract has no effect at the concentrations used for preparation of the AuNPs. ThusAuNPs showed broad spectrum antibacterial activity that may be agood alternative therapeutic approach in future.
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Author Name: Mostafa M.H. Khalil, Ibrahim I. Mahmoud and Mariam O.A Hamed
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Keywords: Nanogold, Laurel leaf extract, Laurus nobilis L., antimicrobial activity, green synthesis.