Natural Flavonoid Glycoside-Based Zinc Oxide Nanoparticles: Compound Isolation, Nanoparticle Green Synthesis, Characterization, and in vitro Antioxidant, Anti-hyperglycaemic and Anti-inflammatory Effects

Introduction: Recent advances in effective and efficient drug delivery have favoured the biological applications of phytochemical-based metal oxide nanoparticles (NPs). Objective: This study, therefore, utilized a flavonoid glycoside, Myricitrin (MY), isolated from Eugenia uniflora as a biogenic substance for the synthesis of zinc oxide nanoparticles (ZnONPs) and evaluated the antioxidant, anti-hyperglycaemic, and anti-inflammatory potentials. Materials and Methods: Flavonoid glycoside was isolated from the leaf of E. uniflora following standard phytochemical techniques for extraction, solvent-partitioning, column chromatography, and thin-layer chromatography. The phytocompound was characterized by NMR and HRESI-MS methods. Zinc oxide NPs were green synthesized using the isolated flavonoid glycoside. The biogenic ZnONPs were characterized using UV-Vis, FESEM, EDX, and XRD techniques. The biological potential of the MY-ZnONPs was based on in vitro analysis. Nitric oxide (NO), H2O2, OH, and O2 - antioxidant methods were used. The anti-hyperglycaemic effect was based on α-amylase and α-glucosidase enzyme inhibition, while the egg albumin denaturation (EAD) method was used to determine the antiinflammatory effect. Results: Flavonoid glycoside was isolated and characterized as myricitrin from E. uniflora. The MY-ZnONPs were green synthesized as a greyish powder. The UV-Vis absorption peaks at 387 and 415 nm match the characteristic peaks for ZnONPs. The FESEM revealed petal-, irregular-, and spindle-shaped NPs of 30-80 nm size, which tend to agglomerate in clusters and bundles. The EDX analysis showed the elemental weight percentage of Zn and O to be 79.83% and 18.51%, respectively, indicating the successful formation of ZnO nanoparticles. The X-ray diffractogram showed the crystallinity of the NPs at 29.23⁰, 36.25⁰, 51.50⁰, 63.67⁰, 72.06⁰, and 78.90⁰. At 100 μg/mL, the NPs demonstrated a comparable 68% inhibition of O₂ - to Quercetin, the standard antioxidant. They inhibited EAD in a dose-de pendent manner, having ≥75% inhibition at 200 μg/mL. Finally, they exhibited notable anti-hyperglycaemic properties against α-amylase and α-glucosidase with IC₅₀ of 89.24±0.63 and 105.95±0.05 μg/mL, respectively. Conclusion: This study has shown MY-ZnONPs as a flavonoid glycoside-based metal oxide nanoparticle with notable antioxidant, anti-diabetic, and anti-inflammatory activities.