Green synthesis of cerium oxide nanoparticles using Quercus infectoria: Characterization and evaluation of antibacterial and antioxidant activities

Cerium oxide nanoparticles (CNP) have gained attention for their unique physical, chemical, and biological properties. This study aims to synthesize CNPs using Quercus infectoria gall extract, and its active components mainly tannic acid (TA), and gallic acid (GA), and compare them with chemically synthesized CNPs. Green synthesis involved adding gall extract, TA, or GA solution to cerium nitrate hexahydrate, followed by reaction at 70 °C and calcination at 500 °C. Characterization employed various methods, including dynamic light scattering, scanning electron microscopy, X-ray diffraction, UV–Vis spectroscopy, and Fourier-transform infrared spectroscopy to respectively characterize hydrodynamic diameter, morphology, crystallinity and purity, and surface functional groups. Antibacterial and antioxidant properties were evaluated using the broth microdilution and DPPH radical scavenging methods, respectively. It confirmed successful synthesis of crystalline CNPs, with UV spectra exhibiting a peak at 290 nm. Antibacterial tests revealed that pre-calcined TA-synthesized NPs, at 25 mg ml −1 , exhibited inhibitory properties against Staphylococcus aureus and Pseudomonas aeruginosa . CNPs synthesized with gall extract at 100 mg ml −1 displayed antibacterial activities against Escherichia coli and S. aureus , while gall extract had highest efficacy on S. aureus with MIC of 1.875 mg ml −1 . GA, TA, and gall extract demonstrated DPPH scavenging activities of 86 %, 59 %, and 66 % at 50 µg/ml, respectively. Antioxidant potential of CNPs at 1 mg ml −1 was 19 %, 20 %, 21 %, and 17 % for GA, TA, gall extract, and chemically synthesized CNPs, respectively. In conclusion, CNPs synthesized in this study can be considered as antioxidants. Further investigation is needed to optimize synthesis methods and achieve desired antibacterial properties, given contradictory findings in prior studies.