Halpeh Extract-Derived Gold Nanoparticles: A Dual Force Against Microbes and for Phytochemical Enhancement

The increasing resistance of pathogenic microorganisms to conventional antibiotics has led to a growing interest in alternative antimicrobial agents. In this study, the antimicrobial activity (antibacterial and antifungal) of aqueous and methanolic extracts of Halpeh plant and gold nanoparticles synthesized using the extract of this plant was investigated. Additionally, the effect of different concentrations of synthesized gold nanoparticles on the phytochemical properties (antioxidant and reducing ability) of Halpeh plant extract was examined. The results of UV-Vis (Ultraviolet-Visible Spectroscopy), XRD (X-Ray Diffraction Analysis), TEM (Transmission Electron Microscopy), SEM (Scanning Electron Microscopy), and FTIR (Fourier Transform Infrared Spectroscopy) tests on gold nanoparticles confirmed their synthesis. SEM and TEM images showed that the gold nanoparticles were spherical in shape with an average size of 22.89 nm. According to the results, the methanolic extract exhibited significantly higher antibacterial and antifungal activity compared to the aqueous extract, with the maximum inhibition zone diameters observed for Escherichia coli (14 mm) and Aspergillus niger (15 mm). Moreover, the antimicrobial activity of gold nanoparticles showed that these nanoparticles have relatively good ability to inhibit gram-negative bacteria, with the largest inhibition zone diameters observed for Escherichia coli (18 mm) and Aspergillus niger (20 mm). The antioxidant and reducing power activity (phenolic flavonoids content) of Halpeh plant extract treated with different concentrations of synthesized gold nanoparticles increased with increasing nanoparticle concentrations up to 60 ppm (IC50 = 9.94 µg/ml and reducing power = 16.85 mMFe2+/mg sample), and decreased at higher concentrations.