Green development, comparative characterization and antioxidant application of biogenic zinc oxide nanoparticles synthesized from Thai medicinal plants

Biogenic zinc oxide nanoparticles (ZnO NPs) were produced via green synthesis of three Thai medicinal plants: neem (Azadirachta indica), garlic (Allium sativum), and galangal (Alpinia galanga). This eco-conscious route offers a safer substitute for conventional chemical methods that rely on toxic reagents. To render the ZnO NPs fit for downstream applications, stringent control over particle size in the nanoscale domain, sustained colloidal stability, and retention of robust antioxidant activity are imperative. Accordingly, the resultant nanoparticles must be subjected to exhaustive physicochemical characterization complemented by quantitative evaluation of their antioxidant. The ZnO NPs characterization was completed by means of zeta potential, energy-dispersive X-ray (EDX), scanning electron microscope (SEM), ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared (FTIR), and dynamic light scattering (DLS). As a result of that, the stable zeta potential was between +35.2 and +36.6 mV, and the nanoparticle sizes were from 47.2 to 49.1 nm. Neem extract-mediated ZnO nanorod NPs exhibited the maximum antioxidant potential, with IC50 = 52.26 μg/ml and scavenging of 74% with DPPH. Results have indicated that the diverse phytochemical profiles of the plant extracts, particularly the neem extract in which the highest increases were observed, and the nature of the phytochemical mixtures that can influence the behavior of the NPs and their antioxidant performance played the main role of controlling the behavior of NPs and their antioxidant activity. Furthermore, the study highlights biogenically synthesized ZnO-NPs as environmentally friendly and safe candidates for both biomedical and agricultural applications