Plants are rich in phytoconstituent biomolecules that served as a good source of medicine. More recently, they have been employed in synthesizing metal/metal oxide nanoparticles (NPs) due to their capping and reducing properties. This green synthesis approach is environmentally friendly and allows the production of the desired NPs in different sizes and shapes by manipulating parameters during the synthesis process. The most commonly used metals and oxides are gold (Au), silver (Ag), and copper (Cu). Among these, Cu is a relatively low-cost metal that is more cost-effective than Au and Ag. In this review, we present an overview and current update of plant-mediated Cu/copper oxide (CuO) NPs, including their synthesis, medicinal applications, and mechanisms. Furthermore, the toxic effects of these NPs and their efficacy compared to commercial NPs are reviewed. This review provides an insight into the potential of developing plant-based Cu/CuO NPs as a therapeutic agent for various diseases in the future.

The increasing prevalence of cancer necessitates the development of novel and effective therapeutic agents. This study evaluates the anticancer potential of biosynthesized copper oxide nanoparticles (CuO NPs) using Camellia sinensis extract against human colon and breast cancer cells. The CuO NPs were characterized using various techniques to confirm their structure, size, morphology, and functional groups. The average size of CuO NPs synthesized was 20–60 nm, with spherical shape. The cytotoxic effects of these CuO NPs reveal a dose-dependent reduction in cell viability with 50% inhibitory concentration (IC₅₀) at 58.53 ± 0.13 and 53.95 ± 1.1 μg/mL, respectively. Further investigation into the mechanism of action was conducted using flow cytometry and apoptosis assays, which indicated that CuO NPs induced cell cycle arrest and apoptosis in cancer cells. Reactive oxygen species (ROS) generation, caspase activity assay, and comet assay were also performed to elucidate the underlying pathways, suggesting that oxidative stress and DNA damage play pivotal roles in the cytotoxicity observed. Overall, our findings demonstrate that biosynthesized CuO NPs exhibit notable anticancer activity against colon and breast cancer cells, with moderate selectivity over normal cells, highlighting their potential as a therapeutic agent due to their biocompatibility. However, further studies are required to validate their selectivity and safety profile.