EGCG Derivatives Alleviate Diquat-Induced Liver and Gut Damage in Mice by Activating an Antioxidant Pathway and Enhancing Barrier Function.

(-)-Epigallocatechin 3-gallate (EGCG) is a potent natural antioxidant, but its strong bitterness and poor palatability limit its application in animal production. This study aimed to evaluate the protective effects and underlying mechanisms of chemically synthesized EGCG derivatives against oxidative stress using a diquat-induced mouse model. A total of 36 male ICR mice were randomly assigned into six groups (n = 6): Control (T0), Diquat (T1), EGCG + Diquat (T2), Epigallocatechin octanoate (EGCO) + Diquat (T3), Epigallocatechin p-chloromethylbenzoate (EGCP) + Diquat (T4), and Epigallocatechin ibuprofen ester (EGCI) + Diquat (T5). Oxidative stress was induced by intraperitoneal injection of diquat at day 27 of the experiment, while EGCG or its derivatives were administered via dietary supplementation. At day 28, the mice were weighed, killed, and the tissues were sampled. Diquat challenge significantly impaired growth, increased serum injury markers (ALT, AST, DAO, and D-LA) (p < 0.05), suppressed hepatic and jejunal antioxidant enzymes (GPx, SOD, and TAOC) while elevating MDA (p < 0.05), damaged jejunal morphology (villus atrophy) (p < 0.05), and downregulated tight junction proteins (ZO-1 and Occludin) (p < 0.05). Chemically synthesized EGCG derivatives, especially EGCI, effectively alleviated diquat-induced growth impairment and hepatic and intestinal oxidative damage by improving intestinal barrier function and enhancing systemic antioxidant capacity, possibly in part through activation of the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) signaling pathway. Compared with EGCG, EGCI exhibited reduced bitterness and improved palatability, which favored normal feed intake. These findings provide strong theoretical support for the future application of EGCG derivatives, especially EGCI, as functional antioxidant additives in broiler production.