Biosynthesis of Gold Nanoparticles by Essential oil of Diplotaxis acris, Characterization and Antimicrobial activities MOHAMEd HABIB OUESLATI1,2* LOTFI BEN TAHAR1,2,3, A. KHUzAIM ALzAHRANI4, JAMITH BASHA4 and OMAR H. ABd ELKAdER5

The present work reports a green biosynthesis of gold nanoparticles (EO-AuNPs) using an Essential oil (EO) as a reducing agent of the Au(III) in HAuCl4. The EO was extracted by hydro-distillation from Diplotaxis acris flowers. A total of 16 compounds were detected from the EO oil by using GC–MS and 5-methylsulfanylpentanenitrile was identified as the major component (73.60 %). The biosynthesized EO-AuNPs were characterized performing UV–Vis, IR, XRD and TEM analyses. The UV-Vis revealed the typical features of surface plasmon resonance (SPR) of AuNPs at ~526 nm. The FT-IR spectrum of the biosynthesized nanoparticles exhibited the features of the nitrile (-C≡N) functional group indicating that the -C≡N-bearing EO components are likely acting as reducing and stabilizing agents for the formation of EO-AuNPs. The plausible scheme of EO-AuNPs formation was proposed. The TEM analysis showed that the EOAuNPs were almost spherical in shape with an average particle size of 12.7 nm. In addition, the antimicrobial activity was carried out by diffusion of agar wells method. The results proved that the EO-AuNPs displayed a potential antimicrobial against Gram-negative strains, with a maximum zone of inhibition of 16 mm for E. coli at a concentration of 100 μg/mL.