Transformation of flavonoids by intestinal microorganisms
Transformation of flavonoids by intestinal microorganisms
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DOI：
10.1024/0300-9831.73.2.79
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发表时间：
2003-03-01
影响因子：
2.3
通讯作者：
Braune, A
中科院分区：
文献类型：
--
作者：
Blaut, M;Schoefer, L;Braune, A
水果、蔬菜和谷物含有丰富的次生植物代谢物，这些代谢物与促进健康有关。为了了解它们的作用机制，有必要获得更多关于它们摄入后在体内的命运的信息。摄入的一定比例的次生植物成分可能会逃避小肠的吸收，因此会被肠道微生物或肠肝循环转化。为了研究细菌对次生植物代谢物的转化，从人类粪便中分离出支枝真杆菌，并与选定的黄酮类化合物一起孵育。 E. ramulus 是一种严格厌氧细菌，被发现存在于大多数受调查个体的胃肠道中。 E. ramulus 裂解几种黄酮醇和黄酮的环系，分别产生相应的羟基苯乙酸和羟基苯丙酸，以及乙酸盐和丁酸盐。根据高效液相色谱（HPLC）和高效液相色谱联用质谱（LC-MS）检测的中间体以及催化花旗松素异构化、根皮素水解和间苯三酚还原等反应的酶的检测，提出了降解途径。脱芳构间苯三酚还原酶。可能是所有类黄酮降解途径的一部分，被纯化和表征。利用新开发的荧光测试进行活性筛选，从 E. ramulus 基因库中克隆了编码根皮素水解酶的基因。此外，通过MS和H-1和C-13 NMR分析发现并鉴定了一种新的中间体为α-α-钙宁。为了研究 E. ramulus 在体内条件下的降解潜力，将无菌大鼠与 E. ramulus 相关联。灌胃应用槲皮素-3-葡萄糖苷后。分析了限生大鼠的尿液和粪便中源自槲皮素-3-葡萄糖苷的降解产物。在与 E. ramulus 单一结合的大鼠粪便中，发现了 3,4-二羟基苯乙酸，表明该生物体能够在体内条件下裂解槲皮素。为了研究膳食类黄酮含量如何影响人类肠道中的 E. ramulus 细胞计数，十二名受试者食用不含类黄酮的饮食一周，并在此期间的某一时刻摄入大剂量的类黄酮。通过原位杂交分析了研究两个阶段的粪便样本中的细菌总数和 E. ramulus 计数。在不含类黄酮期间，总细胞计数和枝条细胞计数显着下降，而在富含类黄酮期间，枝条细胞计数增加高达10倍，表明膳食次生植物代谢物可能对肠道菌群产生影响。 E.ramulus还能够将异黄酮类染料木黄酮和黄豆苷元分别转化为产物2-(4-羟基苯基)-丙酸和O-去甲基安哥拉素。
Fruit, vegetables and cereals contain a wealth of secondary plant metabolites which have been implicated in the promotion of health. To understand the mechanism of their action it is necessary to gain more information on their fate in the body following ingestion. A certain proportion of ingested secondary plant constituents may escape absorption in the small intestine and therefore undergo transformation by intestinal microorganisms or enterohepatic circulation. To study the transformation of secondary plant metabolites by bacteria, Eubacterium ramulus was isolated from human feces and incubated with selected flavonoids. E. ramulus is a strictly anaerobic bacterium which was found to be present in the gastrointestinal tract of most individuals investigated. E. ramulus cleaves the ring system of several flavonols and flavones giving rise to the corresponding hydroxyphenylacetic and hydroxyphenylpropionic acids, respectively, as well as acetate and butyrate. Degradation pathways were proposed based on the intermediates detected by high performance liquid chromatography (HPLC) and HPLC coupled with mass spectrometry (LC-MS) and the detection of enzymes that catalyze reactions such as taxifolin isomerization, phloretin hydrolysis and phloroglucinol reduction. The dearomatizing phloroglucinol reductase. presumably part of all flavonoid degradation pathways, was purified and characterized. The gene encoding phloretin hydrolase was cloned from a E. ramulus gene library taking advantage of a newly developed fluorescence test for activity screening. Moreover, a new intermediate was discovered and identified by MS and H-1 and C-13 NMR analysis as alphitonin. To investigate the degradational potential of E. ramulus under in vivo conditions, germfree rats were associated with E. ramulus. Following the intragastric application of quercetin-3-glucoside. urine and feces of gnotobiotic rats were analyzed for degradational products originating from quercetin-3-glucoside. In feces of rats monoassociated with E. ramulus, 3,4-dihydroxyphenyl acetic acid was found, indicating that this organism is able to cleave quercetin under in vivo conditions. To investigate in which way the dietary flavonoid content affects the cell counts of E. ramulus in the human intestinal tract, twelve human subjects consumed a flavonoid-free diet for one week and at one point during this period a large dose of flavonoids. Fecal samples from both phases of the study were analyzed by in-situ hybridization for total bacterial counts and counts of E. ramulus. Total cell counts and the cell counts of E. ramulus decreased significantly during the flavonoid-free period, while there was an increase in the E. ramulus counts of up to 10-fold during the flavonoid-rich period indicating that dietary secondary plant metabolites may have an influence on the intestinal microflora. E. ramulus is also capable of converting the isoflavonoids genistein and daidzein to the products 2-(4-hydroxyphenyl)-propionic acid and O-desmethylangolensin, respectively.