Green synthesis of copper nanoparticles using Justicia glauca Rottler: Insights into oxidative stress mechanisms and evaluation of antibacterial, antidiabetic and cytotoxicity activity

Copper nanoparticles (CuNPs) were synthesized via a green and environmentally friendly method using Justicia glauca Rottler leaf extract. The formation of CuNPs was confirmed by UV–vis spectroscopy (585 nm), while FTIR analysis identified the reactive groups (O–H, N–H, C–N) responsible for the stabilisation of the nanoparticles. SEM micrographs revealed mostly irregular and agglomerated particles, and EDX analysis confirmed a high copper content (100%). XRD analysis showed a crystalline structure with an average particle size of 17.42 nm. The synthesized CuNPs showed significant antibacterial activity against Escherichia coli , Staphylococcus aureus, Pseudomonas aeruginosa , and Klebsiella pneumoniae . Biotoxicity tests performed using Artemia salina showed an LC₅₀ value of 39.63 µg/mL, indicating preliminary assessment of nanoparticle toxicity. Furthermore, CuNPs exhibited potent inhibitory activities against α-amylase (70.50%) and α-glucosidase (71.04%), indicating strong anti-diabetic potential. Overall, this study highlights the dual biomedical and environmental significance of CuNPs derived from J. glauca as durable, biocompatible nanomaterials with promising antimicrobial and antidiabetic applications.