Abstract: Currently, few studies have reported on the direct use of tea extracts as raw materials for creating novel functional composites. This study successfully synthesized Guangyuan Yellow Tea-Zinc Nanocomposites (Y-Zn) using Guangyuan Yellow Tea infusion and zinc sulfate as raw materials through a green, simple one-step self-assembly method. Characterization via UV-vis spectrophotometry, transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) reveals that the synthesized nanocomposite exhibits uniform particle size and excellent dispersion. Antibacterial experiments demonstrated that Y-Zn exhibits dose-dependent antibacterial effects against multiple Gram-positive bacteria, including drug-resistant strains, and effectively inhibits bacterial biofilm formation. Antioxidant experiments revealed its excellent free radical scavenging ability, achieving over 80% scavenging efficiency at a concentration of 20 μg·mL^-1. Cellular experiments confirmed that Y-Zn suppresses lipopolysaccharide (LPS)-induced macrophage inflammatory responses by downregulating inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression. Furthermore, zebrafish models demonstrated its favorable biosafety profile. In summary, this study directly utilized tea infusion as the subject to develop a self-assembled composite that possesses multiple biological activities and safety, providing insights into the application of China's abundant tea resources in the field of life sciences and health.

Key words: tea infusion, self-assembly, nanocomposite, antibacterial activity, anti-inflammatory activity