Green Synthesis of Selenium, Zinc Oxide, and Strontium Nanoparticles and Their Antioxidant Activity - A Comparative In Vitro Study

Background Antioxidants are vital in reducing oxidative stress, a key factor in the pathogenesis of many chronic diseases, including cancer, cardiovascular disease, and neurodegenerative disorders. The aim of our study is to analyze and compare the oxidative potential of biosynthesized selenium, strontium, and zinc oxide nanoparticles (NPs). Materials and methods Selenium nanoparticles (SeNPs) were synthesized using 20 mM of sodium selenite as the precursor and 1 g each of Cymbopogon citratus and Syzygium aromaticum as reducing and stabilizing agents. Strontium nanoparticles (SrNPs) were synthesized with 30 mM of strontium chloride as the precursor and 1 g of Acacia nilotica as a reducing and stabilizing agent. Zinc oxide nanoparticles (ZnONPs) were synthesized using 30 mM of zinc nitrate as the precursor and 1 g each of Cuminum cyminum and Syzygium aromaticum as reducing and stabilizing agents. Selenium, strontium, and zinc oxide nanoparticles were characterized using Fourier-transform infrared spectroscopy (FT-IR) analysis. The antioxidant activity of biogenically synthesized strontium, selenium and zinc oxide nanoparticles was examined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay (DPPH assay) and hydroxyl radical scavenging assay (H₂O₂ assay). Results The FT-IR spectra of selenium nanoparticles revealed a peak at 3327.990 cm^-1, strontium nanoparticles at 3332.331 cm^-1, and zinc oxide nanoparticles at 3216.346 cm^-1. The significant results for the green-synthesized selenium, strontium, and zinc oxide nanoparticles were observed in antioxidant assays. The results from the DPPH assay show that at the highest concentration of 50 µL, SrNPs exhibited 90.12 % inhibition, SeNPs displayed 90.12% inhibition, and ZnONPs showed 89.55% inhibition. In the H₂O₂ assay, at the highest concentration of 50 µL, SrNPs showed 87.43% inhibition, SeNPs displayed 85.11% inhibition, and ZnONPs exhibited 84.66% inhibition. SrNPs demonstrated a higher percentage of inhibition in both the DPPH and H₂O₂ assays. Maximum inhibitory activity was observed at the highest concentration. However, the prepared nanoparticles showed a slightly lower percentage of inhibition when compared to the standard. Conclusion Strontium nanoparticles synthesized based on Acacia nilotica demonstrated excellent antioxidant activity compared to the synthesized selenium and zinc oxide nanoparticles. Therefore, the study suggests that the produced strontium nanoparticles can serve as an antioxidant agent, owing to their remarkable free radical scavenging activity.