Does thermal processing improve intestinal antioxidant function of key tea components? A comparative study on...

Tea polyphenols and theabrownin possess antioxidant properties, but thermal processing effects on their composition and intestinal protection are unclear. This study used oxidized fish oil (peroxide value: 28.87 mmol/kg) to simulate dietary exposure to oxidized lipids, inducing oxidative stress and intestinal barrier impairment in rats. Heating reduced tea polyphenols (10.3 %), diminishing their protective effect, as evidenced by a 4.6-fold rise in ROS-positive cells (2.6 % to 12.1 %) and decreased activation of NRF2 signaling pathway. Conversely, thermal processing increased the levels of low-molecular-weight compounds in theabrownin (e.g., Teadenol A), and theabrownin maintained antioxidant bioactivity after heating, as indicated by a 25.6 % increase in BCL2/BAX ratio and cytoprotective effects. These findings indicate that theabrownin exhibits thermal stability with maintained antioxidant functionality, while tea polyphenols undergo significant alterations. This supports the potential application of thermostable theabrownin as a functional food ingredient targeting oxidative stress-related intestinal damage.