Citrus Extract-Mediated Zinc Oxide Nanoparticles and Their Capacity to Attenuate Free Radicals and Inflammation

Introduction: The exploitation of plant materials for the green synthesis of nanoparticles (NPs) for biological applications, is considered an eco-friendly technology because it does not involve the use of toxic chemicals. Objective: The study was carried out to synthesize citrus extract-mediated ZnO NPs and evaluate their free radical scavenging and anti-inflammatory capacity. Materials and Methods: ZnO NPs were green synthesized, using the peel and leaf aqueous extracts of three citrus plants: Nova mandarin, Satsuma mandarin and Eureka lemon. The citrus extract based ZnO NPs were characterized by UV-Vis and FTIR spectroscopy, microscopy (SEM and TEM), EDX and XRD analyses. They were screened against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) free radicals. Finally, their inhibitory effects against egg albumin denaturation (EAD) were determined spectrophotometrically. Results: The six afforded biogenic NPs consistently exhibited FTIR vibrational band around 500 cm-1, which is characteristics of a metal oxide (Zn-O) band. They also showed UV-Vis absorption peaks at 387 and 415 nm, suggesting the formation of ZnO NPs. Nova mandarin peel (NMP) ZnO NPs exhibited the best DPPH and NO radical scavenging activities, with 50% inhibitory concentration (IC50) of 7.61±0.69 and 19.93±0.40 μg/mL, respectively. It also gave the best inhibition against EAD, with an IC50 of 14.80±1.29 μg/mL. Morphological assessment of NMP extract-based ZnO NPs revealed rod-shaped particles at 35-50 nm range. Conclusion: It has been shown through this study that citrus extract based ZnO NPs, especially those prepared with NMP, may have the capacity to attenuate free radical release and inflammation in biological systems.