Green synthesis, characterization, and biological activities of copper oxide nanoparticles using Origanum vulgare extract.

The growing demand for eco-friendly nanomaterials has accelerated interest in green synthesis strategies using medicinal plants. In this study, copper oxide nanoparticles (CuO NPs) were synthesized with an aqueous extract of Origanum vulgare as a natural reducing and stabilizing agent in a simple, low-cost, and sustainable bioprocess. The nanoparticles were characterized by FTIR, XRD, SEM-EDS, and TGA-TDA, confirming their nanocrystalline structure, monoclinic phase, and thermal stability. Surface functionalization with phytochemicals was evidenced by FTIR and elemental analyses, indicating strong Cu - biomolecule interactions. Phytochemical assays confirmed retention of phenolics, flavonoids, and tannins, while mineral profiling (ICP-AES, WD-XRF) revealed Ca, Mg, Fe, and Cu contributing to nucleation. HPLC-UV-MS identified bioactive compounds such as rosmarinic acid and rutin. Functionally, the CuO NPs exhibited strong antioxidant activity (DPPH, ABTS, FRAP) and broad-spectrum antimicrobial efficacy against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and fungi (Aspergillus flavus, Botrytis cinerea), surpassing the aqueous extract. These activities, attributed to reactive oxygen species (ROS) generation and Cu2+-biomolecule interactions, highlight the biocatalytic role of plant metabolites in nanoparticle functionality.