After the formation of copper hydroxide, it is converted into copper oxide through calcination or heat treatment . This process involves dehydrating the hydroxide, resulting in the formation of the corresponding metal oxide . However, sodium hydroxide is a corrosive reagent that requires proper handling and disposal. In this study, a green approach was used to synthesize copper oxide, using only yerba mate extract and the metal precursor salt, to reduce environmental impact and ensure a safe route. In this methodology, the reaction between the copper nitrate and the bioactive compounds presents in the yerba mate extract results in an acidic solution (pH=4).