Biosynthesis of silver oxide Nanocubes Ag2O-NPs via achlorophyllous plant: Cistanche tubulosa, chemical profiling, characterization and antibacterial activity

This study presents the biosynthesis of silver oxide nanoparticles (Ag₂O-NPs) mediated by the hexane extract of Cistanche tubulosa , an achlorophyllous holoparasitic plant, and assesses their antibacterial and antibiofilm properties against some pathogenic bacteria strains. GC–MS analysis of the hexane extract revealed 22 compounds dominated by lipophilic metabolites, such as fatty acids, fatty acid esters, hydrocarbons and oxygenated derivatives. These constituents may contribute to a phytochemical environment that supports NPs formation, surface association, and colloidal stabilization. The resulting Ag₂O-NPs were characterized using UV–Vis spectroscopy, XRD, XPS, FTIR, FESEM, DLS, and zeta potential analysis. The characterization results confirmed the formation of crystalline cubic Ag₂O-NPs with an average crystallite size of 22.1 ± 1.9 nm, cubic-like morphology, hydrodynamic diameter of 56.8 ± 3.4 nm, and negative zeta potential of −27.6 ± 1.1 mV, indicating stable colloidal behavior. The Ag₂O-NPs showed species-dependent antibacterial activity, with MIC values of 16, 32, 64, and 64 μg/mL against Escherichia coli , Streptococcus mutans , klebsiella pneumoniae , and Pseudomonas aeruginosa , respectively. Growth inhibition analysis further showed IC₅₀ values of 16 μg/mL for E. coli , 34 μg/mL for S. mutans , 36 μg/mL for K. pneumoniae , and > 50 μg/mL for P. aeruginosa . The Ag₂O-NPs also exhibited concentration-dependent antibiofilm properties. At 160 μg/mL, biofilm inhibition reached 90.00 ± 2.00% against E. coli , 84.00 ± 2.00% against S. mutans , 80.00 ± 2.00% against K. pneumoniae , and 78.67 ± 1.15% against P. aeruginosa . Overall, the results demonstrate that C. tubulosa hexane extract can serve as a lipophilic phytochemical source for producing stable Ag₂O-NPs with antibacterial and antibiofilm activity against the selected pathogenic bacterial strains.