Laboratory of Tea Function R&D Food Research Laboratories, Mitsui Norin Co, Ltd, Fujieda-shi, Shizuoka 426-0133, Japan.
J Agric Food Chem. 2010 Jan 27;58(2):1313-21. doi: 10.1021/jf903375s.
Anaerobic metabolism of (-)-epigallocatechin gallate (EGCg) by rat intestinal bacteria was investigated in vitro. First, intestinal bacteria which are capable of hydrolyzing EGCg to (-)-epigallocatechin (EGC) and gallic acid (2) were screened with 169 strains of enteric bacteria. As a result, Enterobacter aerogenes, Raoultella planticola, Klebsiella pneumoniae susp. pneumoniae, and Bifidobacterium longum subsp. infantis were found to hydrolyze EGCg. Subsequent steps of EGCg metabolism are degradation of EGC (1) by intestinal bacteria. Then, EGC was incubated with rat intestinal bacteria in 0.1 M phosphate buffer (pH 7.1) and the degradation products were analyzed with time by HPLC or LC-MS. Further, the products formed from EGC were isolated and identified by LC-MS and NMR analyses. The results revealed that EGC was converted first to 1-(3',4',5'-trihydroxyphenyl)-3-(2'',4'',6''-trihydroxyphenyl)propan-2-ol (3) by reductive cleavage between 1 and 2 positions of EGC, and subsequently metabolite 3 was converted to 1-(3',5'-dihydroxyphenyl)-3-(2'',4'',6''-trihydroxyphenyl)propan-2-ol (4) followed by the conversion to 5-(3,5-dihydroxyphenyl)-4-hydroxyvaleric acid (5) by decomposition of the phloroglucinol ring in metabolite 4. This degradation pathway was considered to be the major route of EGCg metabolism in the in vitro study, but two minor routes were also found. In addition to the in vitro experiments, metabolites 3, 4, 5, and 6 were detected as the metabolites after direct injection of EGC into rat cecum. When EGCg was administered orally to the rats, metabolites 4, 5, 6, 11, and 12 were found in the feces. Among the metabolites detected, metabolite 5 was dominant both in the cecal contents and feces. These findings suggested that the metabolic pathway of EGCg found in the in vitro study may be regarded as reflecting its metabolism in vivo.
本研究采用体外实验的方法，研究了大鼠肠道细菌对（-）-表没食子儿茶素没食子酸酯（EGCg）的厌氧代谢。首先，我们筛选了 169 株肠道细菌，以寻找能够将 EGCg 水解为（-）-表儿茶素（EGC）和没食子酸（2）的细菌。结果发现，产气肠杆菌、植生赖特氏菌、肺炎克雷伯菌悬液和婴儿双歧杆菌能够水解 EGCg。EGCg 代谢的后续步骤是肠道细菌对 EGC（1）的降解。然后，我们将 EGC 与大鼠肠道细菌一起在 0.1 M 磷酸盐缓冲液（pH 7.1）中孵育，并通过 HPLC 或 LC-MS 随时间分析降解产物。此外，我们还通过 LC-MS 和 NMR 分析分离和鉴定了 EGC 的产物。结果表明，EGC 首先通过 EGC 1 位和 2 位之间的还原裂解转化为 1-（3'，4'，5'-三羟基苯基）-3-（2'，4'，6'-三羟基苯基）-2-丙醇（3），然后代谢产物 3 转化为 1-（3'，5'-二羟基苯基）-3-（2'，4'，6'-三羟基苯基）-2-丙醇（4），随后通过代谢产物 4 中环庚三醇环的分解转化为 5-（3，5-二羟基苯基）-4-羟基戊酸（5）。该降解途径被认为是 EGCg 在体外研究中的主要代谢途径，但也发现了两条次要途径。除了体外实验外，我们还在直接将 EGC 注入大鼠盲肠后检测到代谢产物 3、4、5 和 6。当 EGCg 口服给予大鼠时，在粪便中发现了代谢产物 4、5、6、11 和 12。在所检测到的代谢产物中，代谢产物 5 在盲肠内容物和粪便中均占优势。这些发现表明，我们在体外研究中发现的 EGCg 代谢途径可能反映了其在体内的代谢。
