Nano-Elicitation of Secondary Metabolism and Antioxidant Potential in Iraqi Centaurea hyalolepis using Silver Nanoparticles

The genus Centaurea contains many medicinal species such as Centaurea hyalolepis Iraqi with abundant potential secondary metabolites with antioxidant activities. The aim of this study was to assess the stimulation of secondary metabolism and increased the antioxidant capacity of Centaurea hyalolepis Iraqi under controlled environment at the presence of AgNPs. The methodology synthetizing silver nanoparticles (AgNPs) using C. hyalolepis extract is detailed the experimental section and the synthesized AgNPs were characterized using ultraviolet-visible spectroscopy, scanning electron microscope (SEM), dynamic light scattering (DLS), and X-Ray diffraction (XRD). Foliar spraying was performed with the different concentrations of nano-silver (10, 25, 50 and 100 mg/L) for two weeks. The total phenolic content (TPC) and free radical scavenging activity (DPPH) were then determined. The results showed that the prepared silver nanoparticles were spherical in shape with average diameter of 34.5±10.2 nm, characterized by a stable negative zeta charge. The total phenolic content (TPC) showed a significant increase with the concentration of AgNPs, resulting in an 89.1% increase in plants treated with 100 mg/L of AgNPs than untreated plants. The IC₅₀ value (concentration at which 50% of the free radicals are scavenged) for antioxidant activity was also significantly lower at a concentration of 100 mg/L, demonstrating a noteworthy effectiveness of antioxidant property. This study concludes that nano-elicitation with 100 mg/L silver nanoparticles is optimal for enhancing the production of phenolic compounds and the antioxidant activity of Centaurea hyalolepis.