Green Synthesis of Silver and Zinc Oxide Nanoparticles from Black Rice Extract with Antioxidant, Cytotoxic, and Anticancer Activities Against MCF-7 and THP-1 Cell Lines

The synthesis of metal oxide nanoparticles using extracts from therapeutic plants is a promising substitute for conventional chemical processes. This study explored various secondary metabolites in Black rice (Oryza sativa L.), including flavonoids, tannins, and alkaloids, which aid in the eco-friendly production of silver and zinc oxide nanoparticles. The formation of these nanoparticles is confirmed by UV–vis spectral analysis, which showed peaks at 411.9 nm for silver and 368 nm for zinc oxide. FTIR spectra indicated the role of plant metabolites in nanoparticle synthesis. SEM and XRD analyses revealed that silver nanoparticles are spherical (average size 45.46 ± 7.56 nm) with a face-centered cubic structure, while zinc oxide nanoparticles are spherical (average size 33.67 ± 12.86 nm) with a hexagonal wurtzite structure. The elemental composition of the samples is assessed using EDX analysis. The silver nanoparticles in the DPPH assay are 32.90 ± 1.51 µg mL⁻¹, outperforming zinc oxide nanoparticles (91.48 ± 1.96 µg mL⁻¹) and the plant extract (67.45 ± 1.82 µg mL⁻¹). Silver nanoparticles also showed significant cytotoxicity with an IC50 of 101.8 ± 0.1834 µg mL⁻¹ against MCF-7 cells, compared to 623.6 ± 0.08807 µg mL⁻¹ for zinc oxide. For THP-1 cell lines, the IC50 values are 19.19 ± 0.2109 for silver and 57.39 ± 0.108 µg mL⁻¹ for zinc oxide. Silver and zinc oxide nanoparticles from black rice extract exhibited strong antioxidant and anticancer properties.