Phytogenic Synthesis of CuO–ZnO Bimetallic Nanoparticles Using Cheilocostus speciosus and Gardenia gummifera Leaf Extracts: Design, Structural Analysis and Multifunctional Antioxidant, Antimicrobial, and Anticancer Activities

In this study, the anticancer, antioxidant, and antimicrobial properties of sustainable CuO–ZnO bimetallic nanoparticles synthesized using aqueous leaf extracts of Cheilocostus speciosus (CS) and Gardenia gummifera (GG) were explored. The extracts acted as natural reducing, stabilizing, and capping agents. The average crystallite sizes of CZCS and CZGG nanoparticles were approximately 30 and 35 nm, respectively, determined by Debye–Scherrer’s equation. UV-Vis and FT-IR spectra confirmed nanoparticle formation, while EDS analysis indicated the proportional presence of CuO and ZnO in both samples. XRD patterns revealed monoclinic CuO and hexagonal ZnO phases, consistent with high crystallinity. XPS confirmed the elemental composition and oxidation states. SEM and TEM analyses showed rod-shaped (CZCS) and spherical (CZGG) nanoparticles, with sizes ranging from 31–90 nm and 38–83 nm, respectively. Both samples, CZCS and CZGG NPs demonstrated potent antibacterial activity against Escherichia coli having ZOI of 23, 25 mm and against Staphylococcus aureus of 14, 20 mm at 100 μL respectively. The antifungal efficacy of CZCS and CZGG NPs against Aspergillus niger having ZOI of 14 and 23 mm at 100 μL respectively. The DPPH assay revealed vigorous antioxidant activity with 96.3% (CZCS), 94.4% (CZGG), and 98.6% (ascorbic acid) inhibition. Moreover, MTT cytotoxicity assays on A549 cancer cells showed significant anticancer effects, with 71.49±0.79% (CZCS) and 67.9±6.39% (CZGG) inhibition at 100 μg/mL. • Green synthesis of copper oxide–zinc oxide nanoparticles using leaf extract of Cheilocostus speciosus and Gardenia gummifera . • Formation of rod-shaped and spherical-shaped nanoparticles showing high crystallinity and stability. • Strong antibacterial, antifungal, and antioxidant activities comparable to ascorbic acid. • Significant anticancer efficacy against A549 cells via mitochondrial impairment. • Eco-friendly bimetallic nanoparticles with potential for biomedical and industrial applications.