Sustainable Engineering of ZnO Nanoparticles via Green Synthesis Using Rhinacanthus nasutus Leaf Extract: Structural Characterization, Antioxidant and Cytotoxicity Functional Applications
Keerthana R., Thirunavukarasu Jayaraman, Dharmalingam KirubakaranABSTRACT
The present study aimed to synthesize zinc oxide nanoparticles (ZnONPs) using the aqueous leaf extract of Rhinacanthus nasutus through an eco‐friendly green synthesis approach and to evaluate their physicochemical characteristics and biological activities. Qualitative phytochemical screening confirmed the presence of alkaloids, flavonoids, phenols, tannins, saponins, carbohydrates, and fixed oils, which facilitated nanoparticle reduction and stabilization. The formation of ZnONPs was confirmed by a characteristic UV‐visible absorption peak at 421 nm. Fourier transform infrared (FTIR) analysis identified the functional groups responsible for nanoparticle capping, while XRD analysis verified the crystalline hexagonal wurtzite structure. SEM analysis revealed predominantly spherical to irregular agglomerated nanoparticles with sizes ranging from 70 to 120 nm, and EDX confirmed the elemental composition of Zn, O, and C. The synthesized ZnONPs exhibited concentration‐dependent antioxidant activity, showing up to 80% DPPH and 85% ABTS radical scavenging at 100 µg/mL. MTT assay demonstrated significant cytotoxicity against A431 human epidermoid carcinoma cells with an IC 50 value of 42.81 µg/mL. Acridine orange staining and intracellular ROS analysis indicated apoptosis through oxidative stress‐mediated pathways. These findings suggest that R. nasutus ‐mediated ZnONPs possess promising antioxidant and anticancer potential for future biomedical applications.