Green synthesis and physicochemical characterization of copper oxide nanoparticles mediated by Mentha spicata leaf extract and their antioxidant, antidiabetic, anti-inflammatory, and cytotoxic activities

Copper oxide nanoparticles (CuO NPs) were synthesized via a green, plant-mediated approach using aqueous leaf extract of Mentha spicata as a natural reducing and stabilizing agent. The formation of CuO NPs was confirmed by UV–visible spectroscopy, exhibiting a characteristic absorption peak around 290 nm. Fourier transform infrared spectroscopy (FTIR) analysis revealed the involvement of phytochemicals such as polyphenols and flavonoids in nanoparticle reduction and stabilization. X-ray diffraction (XRD ) analysis confirmed the formation of phase-pure monoclinic CuO, while scanning electron microscope (SEM) images showed predominantly spherical nanoparticles with sizes ranging from 60 to 80 nm. Elemental composition was verified using energy-dispersive X-ray and a zeta potential of −31.5 mV indicated good colloidal stability. The synthesized CuO NPs exhibited concentration-dependent biological activities. In vitro antioxidant activity showed an IC 50 of 152.53 μg/mL, while α-amylase inhibition demonstrated antidiabetic potential with an IC 50 of 163.38 μg/mL. Anti-inflammatory activity, assessed via protein denaturation assay, yielded an IC 50 of 149.94 μg/mL. Furthermore, the nanoparticles displayed significant cytotoxicity against A375 melanoma cells with an IC 50 of 54.9 μg/mL, while showing reduced toxicity toward L929 normal cells (IC 50 = 83.6 μg/mL), indicating moderate selectivity. Overall, the findings highlight the potential of Mentha spicata -mediated CuO NPs as stable and effective multifunctional nanomaterials for biomedical applications.