Abstract: In this study, amyloid β-protein Aβ₄₂ was incubated with EGCG, TF, TF-3-G, TF-3'-G, TF-DG at the ratio of 1:1 and 1:5 under simulated physiological condition. The contents of β-sheets after incubation were tested by thioflavin T fluorometric assay. It was found that EGCG and theaflavins could suppress the formation of β-sheet structure, thereby inhibiting aggregations of Aβ₄₂. In addition, an SH-SY5Y cell damage model was established and MTT assay was used to examine cell viabilities when 20 μmol·L^-1 Aβ₄₂ was incubated with different concentrations of EGCG and theaflavins (10, 50, 100 μmol·L^-1). Intracellular reactive oxygen species (ROS) levels, antioxidant enzyme activities (GSH-Px) and MDA levels were also measured. The results showed EGCG and theaflavins treatments could alleviate the Aβ₄₂ induced oxidative damage to neural cells by reducing ROS and increasing the activity of GSH-Px. To study the in vivo protective effects of EGCG and theaflavins, SAMP8 mice were treated with 10 mg·kg-1·d^-1 EGCG or theaflavins respectively by gavage for 10 weeks, and the contents of Aβ₄₂ and AGEs in mouse serum were determined. The results showed that EGCG and theaflavins significantly decreased the contents of Aβ₄₂ and AGEs in SAMP8 serum. In summary, EGCG and theaflavins could inhibit the aggregations of Aβ₄₂ and reduce oxidative injury induced by Aβ₄₂ in neural cells, thereby exerting protective effects on AD.

Key words: EGCG, theaflavins, amyloid-β1-42, advanced glycation end products, SH-SY5Y cells, SAMP8 mice