Tea Polyphenol–Zinc Nanocomplexes Alleviate Diquat-Induced Liver and Small Intestine Oxidative Stress in C57BL/6 Mice

Oxidative stress is the key contributor to the onset of numerous diseases. Herein, we develop tea polyphenol-zinc (Tp-Zn) using a metal-polyphenol coordination strategy through a simple hybrid approach. The product is characterized by methods such as dynamic light scattering (DLS), ultraviolet-visible spectroscopy (UV-vis) and transmission electron microscopy (TEM) to evaluate the particle size and potential of Tp-Zn. Oxidative stress was induced in mice by administering diquat (25 mg/kg body weight) followed by pre-treatment with 210 mg/kg body weight tea polyphenols (TPs), 280 mg/kg body weight Tp-Zn, and 70 mg/kg body weight ZnSO₄ for 7 days. Results showed that Tp-Zn treatment significantly improved intestinal barrier function by preventing the diquat-induced down-regulation of tight junction proteins Zonula Occludens protein 1 (ZO-1) and occludin. It also mitigated liver inflammation and damage, as evidenced by reduced serum levels of Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), and Alkaline phosphatase (AKP). Furthermore, Tp-Zn enhanced the antioxidant response in both the intestine and liver by up-regulating the mRNA expression of antioxidant enzymes and reducing the levels of Malondialdehyde (MDA) and reactive oxygen species (ROS) compared to the diquat group (DIQ group). Also, the detection of ROS in the small intestine confirmed Tp-Zn markedly increased intestinal Nuclear factor erythroid 2-related factor 2 (Nrf2) expression compared to the control group. This study aims to clarify that metal-polyphenol coordination with multifaceted regulation of the inflammatory microenvironment could be a novel approach for preventing or treating oxidative stress-related diseases.