Phytosynthesized Ag/MgO nanocomposite from Salvia rosmarinus : a promising multifunctional agent for anticancer, antibacterial, and metabolic enzyme inhibition

Abstract

Plant-mediated synthesis provides a sustainable approach for producing multifunctional nanomaterials. In this study, silver nanoparticles (Ag NPs), magnesium oxide nanoparticles (MgO NPs), and an Ag/MgO nanocomposite (Ag/MgO NCs) were synthesized using Salvia rosmarinus leaf extract and comparatively evaluated. GC–MS and HPLC analyses identified terpenoids, phenolic acids, and flavonoids that may contribute to nanomaterial formation and stabilization. The synthesized materials were characterized using UV–Vis, FTIR, XRD, SEM, TEM, HR-TEM, SAED, EDX mapping, DLS, zeta-potential, TGA/DTG, and nitrogen adsorption–desorption analyses. HR-TEM showed adjacent crystalline domains with lattice spacings of approximately 0.24 and 0.23 nm, tentatively assigned to MgO(111) and Ag(111), respectively, while SAED supported the polycrystalline nature and coexistence of Ag- and MgO-containing domains. Ag/MgO NCs exhibited a TEM-derived particle size of 66.86 ± 28.72 nm, a hydrodynamic diameter of 95.32 nm, a PDI of 0.339, and a zeta potential of −36.4 mV. Ag/MgO NCs exhibited greater antibacterial activity than the individual nanoparticles against Salmonella typhi , Staphylococcus aureus , Enterococcus faecalis , and Klebsiella pneumoniae , producing inhibition-zone diameters of 15–27 mm and MIC values of 62.5–250 μg/mL. TEM observations and increased extracellular protein leakage supported bacterial membrane damage, while biofilm inhibition reached 56.46 % against S. aureus and 61.52 % against K. pneumoniae . Ag/MgO NCs exhibited IC ₅₀ values of 152.37 and 444.23 μg/mL against HeLa and non-cancerous Vero cells, respectively, corresponding to borderline-to-moderate preferential cytotoxicity toward HeLa cells (SI = 2.91). Flow cytometry demonstrated 33.5 % total apoptosis and an increase in the S-phase population from 4.3 % to 32.5 %. The nanocomposite also exhibited improved DPPH and ABTS radical-scavenging activities, with IC ₅₀ values of 140.23 and 275.90 μg/mL, respectively, and inhibited α -amylase and α -glucosidase with IC ₅₀ values of 358.5 and 102.76 μg/mL. Overall, Ag/MgO NCs displayed improved multifunctional biological performance relative to Ag NPs and MgO NPs; however, further mechanistic, biosafety, and in vivo studies are required.