Biological activities of citrus fruit-derived copper oxide nanoparticles: towards sustainable antimicrobial and antioxidant solutions.

The synthesis of CuO NPs from Citrus fruit peel waste is a noteworthy strategy for the effective repurposing utilization of waste and its application in therapeutic studies. Synthesized copper oxide nanoparticles (CuO NPs) from citrus fruit extracts displayed a dark greenish-black colour with sizes ranging from 379.41, 113.19 and 142.76 nm of lemon, orange and tangerine CuO NPs. Phytochemical screening confirmed the presence of phytochemicals in the extracts wherein lemon CuO NPs lacked flavonoids and cardiac glycosides, while orange CuO NPs lacked alkaloids and flavonoids, and tangerine CuO NPs lacked only alkaloids. The decrease in phenolic concentration in CuO NPs was attributed to complex formation with metal ions. Tangerine CuO NPs exhibited the highest antioxidant activity, while lemon CuO NPs showed the highest total antioxidant capacity. Antibacterial activity increased with CuO NP concentration, with tangerine CuO NPs displaying the highest activity against both Bacillus subtilis subtilis strain 168 and Escherichia coli strain PU-1 isolated from Ghagghar river, Haryana, India. This activity was linked to the disruption of bacterial cell membranes and oxidative stress, supported by the interaction between CuO NPs and bacterial cell components. These findings contribute to understanding of various potential applications of citrus fruit-derived CuO NPs in antimicrobial and antioxidant therapies.