Synergistic Dual-Extract Green Synthesis of Zinc Oxide Nanoparticles Using Coriander Stems and Orange Pith: Structural Characterization and In Vitro Biomedical Relevance

A sustainable dual-extract green synthesis of zinc oxide nanoparticles (ZnO NPs) is reported using Coriandrum sativum stem extract and Citrus sinensis pith extract—two underutilized kitchen by-products. Unlike conventional chemical routes and single-extract green syntheses, this synergistic dual-extract approach exploits complementary phytochemicals to achieve enhanced control over nucleation, growth, and stabilization of ZnO nanoparticles. Zinc acetate was employed as the precursor under alkaline conditions, followed by controlled calcination to obtain highly crystalline ZnO NPs. Phenolics and terpenoids from coriander stems facilitated Zn²⁺ reduction, while pectin and flavonoids from orange pith acted as efficient capping and stabilizing agents. Comprehensive characterization confirmed the formation of spherical, monodisperse ZnO NPs with an average size of 24 nm (XRD, TEM) and a sharp UV–Vis absorption peak at 373 nm, corresponding to the wurtzite ZnO phase. FTIR analysis revealed persistent phytochemical functional groups (O–H, C = O, C–O–C), confirming effective surface passivation, while zeta potential measurements (− 28.6 mV) demonstrated excellent colloidal stability. Comparative evaluation with reported green syntheses shows that the present dual-extract system yields smaller and more stable ZnO NPs than single-extract methods. The resulting physicochemical features—uniform size, high surface area, and biocompatible surface chemistry—render these ZnO NPs promising for biomedical applications, particularly anticancer and antidiabetic platforms. This work establishes a reproducible, scalable, and eco-friendly route for high-quality ZnO nanoparticle synthesis with translational potential.