Thirty-three phenolic compounds were identified from the extract of fermented tea (Camellia sinensis L.), including three undescribed flavonoids, namely quamoreokchaside I-II and kamoreokchaside I, along with thirty known compounds. All isolates were tested to evaluate their inhibitory effects against amyloid-beta (Aβ) aggregation through thioflavin-T (ThT) fluorescence-based assay and transmission electron microscopy (TEM). Among the isolates, three tea polyphenols, including (-)-catechin gallate (CG), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin gallate (EGCG), significantly decreased Aβ aggregation at a concentration of 10 μg ml-1, compared to the positive control, Aβ alone. The anti-Aβ aggregation effects of CG, ECG, and EGCG were confirmed again via TEM, which were consistent with the ThT fluorescence-based assay. Moreover, CG and ECG provided stronger protection on SH-SY5Y cells against Aβ-induced cytotoxicity than EGCG. Remarkably, CG showed more potent inhibitory activity than EGCG, the best-known anti-Aβ aggregation agent from tea products.

中文翻译：

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发酵茶（Camellia sinensis）多酚的鉴定及其对淀粉样蛋白-β聚集的抑制活性

从发酵茶 (Camellia sinensis L.) 的提取物中鉴定出 33 种酚类化合物，包括三种未描述的黄酮类化合物，即 quamoreokchaside I-II 和 kamoreokchaside I，以及 30 种已知化合物。通过硫代黄素-T (ThT) 荧光检测和透射电子显微镜 (TEM) 测试所有分离株以评估它们对淀粉样蛋白-β (Aβ) 聚集的抑制作用。在分离株中，三种茶多酚，包括 (-)-儿茶素没食子酸酯 (CG)、(-)-表儿茶素没食子酸酯 (ECG) 和 (-)-表没食子儿茶素没食子酸酯 (EGCG)，在 10 μg 的浓度下显着降低了 Aβ 聚集ml-1，与阳性对照相比，单独的 Aβ。通过 TEM 再次证实了 CG、ECG 和 EGCG 的抗 Aβ 聚集作用，这与基于 ThT 荧光的测定一致。而且，与 EGCG 相比，CG 和 ECG 对 SH-SY5Y 细胞提供更强的保护，以抵抗 Aβ 诱导的细胞毒性。值得注意的是，CG 显示出比 EGCG 更有效的抑制活性，EGCG 是茶产品中最著名的抗 Aβ 聚集剂。