构建EGCG代谢模型寻找黑茶中降脂活性成分及关键代谢菌株

The lipid-lowering activity of dark tea has been widely concerned by domestic and overseas scholars, but the material base of lipid-lowering effects have still been unknown so far. Many studies showed that the lipid-lowering effects of dark tea were enhanced after piling fermentation. The lipid-lowering compounds in dark tea were probably correlated with the biotransformation by fermentation strains, which converted the intrinsic compounds of tea leaves to be a group of metabolites with high bioligical activites. A group of catechins microbial metabolites with potent anti-oxidative and lipid-lowering activities were found in dark tea in our initial research, which pointed out that the lipid-lowering effect of dark tea was related to the metabolites of catechins. In the present project, a representative catechins compound, epigallocatechin gallate (EGCG) was chosen to be studied as projcet. Critical fermentation strains were screened by comparing the metabolic capability of fermentation strains on EGCG in deactivated fresh tea leaves. Then solid-state fermentation of EGCG by individual critical fermentation strain was carried out to study the metabolic pathway of EGCG. Consequently, the metabolites of EGCG were isolated. Metabolites of EGCG were screened by lipid-lowering activity of human hepatocellular liver carcinoma cell line (Hep G2) . Rat hyperlipidemia model was also used to verify the lipid-lowering effect of EGCG metabolites. This project will be contributed to reveal the material base of lipid-lowering efficacy of dark teas, clarify the metabolic pathway of catechins during fermentation of dark teas, and provide a foundation for the fermentation controlling theory of dark teas.

黑茶降脂功效已经受到国内外学者的广泛关注，但是其降脂活性物质基础尚未明确。研究表明渥堆发酵有助于增强黑茶的降脂功效，黑茶的降脂成分可能与发酵菌种的生物转化相关，发酵菌种极有可能将茶叶原有成分转化成为一类高活性的代谢产物。我们前期研究发现黑茶中一组儿茶素类的微生物代谢产物具有很强的抗氧化降脂活性，提示黑茶的降脂功效与儿茶素类的代谢产物有关。本项目以儿茶素类代表性成分-表没食子儿茶素没食子酸酯(EGCG)为研究对象，采用黑茶发酵菌种进行杀青茶叶的固态发酵，筛选具有EGCG代谢能力的关键菌种；利用关键菌种进行EGCG的固态发酵，研究EGCG的代谢途径，获取EGCG的代谢产物，通过人肝肿瘤细胞（Hep G2）降脂模型筛选EGCG代谢产物，采用高血脂动物模型验证EGCG代谢产物的降脂功效，揭示黑茶降脂功效的物质基础，阐明黑茶发酵过程中儿茶素类的代谢途径，为黑茶的发酵控制理论提供依据。

黑茶降脂功效已经受到国内外学者的广泛关注，但是其降脂活性物质基础尚未明确。研究表明渥堆发酵有助于增强黑茶的降脂功效，黑茶的降脂成分可能与发酵菌种的生物转化相关，发酵菌种极有可能将茶叶原有成分转化成为一类高活性的代谢产物。我们前期研究发现黑茶中一组儿茶素类的微生物代谢产物具有很强的抗氧化降脂活性，提示黑茶的降脂功效与儿茶素类的代谢产物有关。本项目1）以儿茶素类代表性成分-表没食子儿茶素没食子酸酯(EGCG)为研究对象，收集了具有典型地域特征的黑茶样品，分离筛选出四种具有EGCG代谢能力的关键菌种，分别是为黑曲霉（Aspergillus niger）、烟曲霉（Aspergillus fumigatus）、Merimbla ingelheimensis和阿姆斯特丹散囊菌（Eurotium amstelodami），2）并进行黑茶发酵菌种进行杀青茶叶的固态发酵，探索了酯型儿茶素和非酯型儿茶素的代谢规律；3）利用关键菌种进行EGCG的液态发酵，研究EGCG的代谢途径，获取EGCG的代谢产物，共分离出6种重要代谢终产物；4）利用筛选所得菌种对茶鲜叶进行固态发酵，研究黑茶特定微生物对茶叶香气的影响，验证单一微生物在黑茶发酵过程中对香气产生的贡献作用，探索了香气的形成机理；5）建立了七种儿茶素在大鼠体内代谢的LC-MS检测方法，采用高血脂动物模型验证高血脂以及高脂膳食（黄油）对茶多酚在体内吸收、分布、代谢和消除的影响；6）研究了发酵-黑茶泾渭茯茶对高血脂动物模型的降脂减肥功效。综上所述，本项目针对茶多酚在黑茶微生物作用下的代谢途径进行了研究，并且还研究了茶多酚在体内ADME, 以及高脂膳食（黄油）干预下以及高血脂症对七种儿茶素的影响。