The copper oxide nanoparticles synthesized using Rhatany root extract involves preparing the Rhatany root extract by adding powdered Rhatany roots to boiling water, allowing the mixture to soak overnight, and removing any solid residue by filtering to obtain the aqueous extract. The copper oxide nanoparticles are prepared by mixing equal volumes of the aqueous Rhatany root extract and 0.1 M aqueous copper sulfate, heating the mixture at 80° C. for 40 minutes, and adding 1 M sodium hydroxide dropwise to the mixture to precipitate CuO. The precipitate is removed by centrifuge, washed with ethanol, dried, and calcined at 400° C. for 4 hours to obtain the copper oxide nanoparticles. The resulting nanoparticles proved effective in degrading wastewater dyes, showed anticancer activity against human cervical cancer by cell viability assay, and showed antibacterial activity against various strains of bacteria by agar diffusion.