Assessment of Antioxidant Property and Characterisation of Citrus Fruit Mediated Green-synthesised Hydroxyapatite Nanoparticles: An In-vitro Study

Introduction: Citrus fruits and their peels are recognised as excellent naturally available antioxidants. Antioxidants play a crucial role in preventing oxidative damage, Deoxyribonucleic Acid (DNA) damage, and protein modification. Therefore, developing compounds from these citrus fruit peels would be highly beneficial. Synthesising compounds of plant origin falls under green synthesis. The rationale behind this study is to create a novel class of biomaterials with improved biological properties, offering significant potential for therapeutic uses. Aim: To assess the antioxidant activity of green-synthesised hydroxyapatite nanoparticles using citrus fruit peel extract. Materials and Methods: This in-vitro study was conducted at the Nanomedicine Biolab, Department of Pharmacology, Saveetha Dental College, Chennai, Tamil Nadu, India, from March 2024 to June 2024. Hydroxyapatite nanoparticles were green-synthesised from Citrus reticulata (orange) and Citrus limonum (lemon). Only the peels of these fruits were included in the green synthesis, which was the primary inclusion criterion. Green-synthesised nanoparticles at different concentrations (10-50 µg/mL) were evaluated for antioxidant properties using the Hydrogen Peroxide assay, the Ferric Reducing Ability of Plasma assay, the 2,2-Diphenyl-1-Picrylhydrazyl assay, the 2,2-Azino-Bis-3-Ethylbenzothiazoline-6-Sulphonic Acid assay, and the Nitric Oxide Radical Inhibition assay. The results were tabulated and statistically analysed using independent t-tests, ANOVA analysis, and post-hoc tests. A p-value of less than 0.05 was considered statistically significant. Characterisation of the generated nanoparticle samples was performed using UV-Vis spectroscopy and Scanning Electron Microscopy (SEM). Results: The successful synthesis of C. reticulata and C. limonum-mediated hydroxyapatite nanoparticles and their comparable antioxidant activity with the standard (ascorbic acid) were observed. The absorbance spectrum ranged from 340 nm to 360 nm in UV-Vis spectroscopy, and distinct morphologies were observed in the SEM analysis. Conclusion: Green-synthesised C. reticulata and C. limonummediated hydroxyapatite nanoparticles exhibited potential antioxidant activity. These green-synthesised nanoparticles possess antioxidant properties.