Food Chemistry, University of Wuerzburg, Am Hubland, 97074, Wuerzburg, Germany.
Eur J Nutr. 2011 Oct;50(7):507-22. doi: 10.1007/s00394-010-0157-0. Epub 2010 Dec 24.
Apples are the most widely consumed fruits in Germany and various other countries. Positive health effects of apple-derived polyphenols in vivo depend on their absorption, metabolism, distribution, and elimination from the body after consumption. Data on the metabolism of these polyphenols in humans are scarce. In order to study the intestinal transit and metabolism of apple polyphenols in humans, a variety of experiments were carried out.
Polyphenols were incubated with saliva (for 5 min), simulated gastric or duodenal juice (4 or 10 h, respectively), or rat hepatocytes (4 h) under aerobic conditions, and with ileostomy fluid under aerobic conditions for 10 h. The polyphenol profile in human serum (8 h later) and renal elimination in urine (24 h later) were also investigated after consumption of 1 L apple juice. Polyphenols and their metabolites were identified and quantified by high-performance liquid chromatography with diode array detection (HPLC-DAD), HPLC-electrospray ionization-tandem mass spectrometry (ESI-MS/MS), and gas chromatography (GC)-MS.
In the presence of native saliva or ileostomy fluid, β-glycosides of phloretin and quercetin were hydrolyzed, to varying degrees depending on the sugar moiety, and to much lesser degrees in the presence of antibiotics. In the gastric milieu, almost complete degradation of procyanidin B(2) to (-)-epicatechin was observed. In the presence of artificial duodenal juice flavan-3-ol epimerization occurred. Quercetin was completely converted to phloroglucinol, 3,4-dihydroxybenzoic acid, and 2,4,6-trihydroxybenzoic acid. Formation of isomeric products of hydroxycinnamic acid esters and their corresponding methyl esters was also observed, and similar results were obtained after incubation with rat hepatocytes. Products of phase II metabolism, two phloretin O-glucuronides and eight (methyl) quercetin O-glucuronides, were identified in the hepatocyte samples. Following enzymatic hydrolysis, 5-caffeoylquinic acid, 4-p-coumaroylquinic acid, caffeic acid, (-)-epicatechin, phloretin, and quercetin were recovered in both serum and urine (5.3% and 3.5% of the amounts consumed, respectively). In addition, 19.5% of the polyphenols consumed were identified in the urine in the form of hydroxylated phenolic and hippuric acids.
The findings relating to the absorption, metabolism, and systemic availability of polyphenols in vivo should contribute to our understanding of their biological effects, and the characterization of newly formed metabolites should facilitate further studies.
苹果是德国和其他许多国家最常食用的水果。苹果中多酚类化合物对人体的积极健康影响取决于它们在摄入后的吸收、代谢、分布和消除。关于这些多酚类化合物在人体中的代谢的数据很少。为了研究苹果多酚在人体中的肠道转运和代谢，进行了各种实验。
多酚类化合物在有氧条件下与唾液（5 分钟）、模拟胃液或十二指肠液（分别为 4 小时或 10 小时）或大鼠肝细胞（4 小时）孵育，在有氧条件下与回肠液孵育 10 小时。在饮用 1 升苹果汁 8 小时后，还研究了多酚类化合物在人血清中的分布和 24 小时后在尿液中的肾消除情况。通过高效液相色谱-二极管阵列检测（HPLC-DAD）、高效液相色谱-电喷雾串联质谱（ESI-MS/MS）和气相色谱（GC）-MS 鉴定和定量多酚类化合物及其代谢物。
在天然唾液或回肠液存在的情况下，根皮苷和槲皮素的β-糖苷，根据糖部分的不同，不同程度地水解，而在存在抗生素的情况下则较少程度地水解。在胃环境中，观察到原花青素 B(2)几乎完全降解为 (-)-表儿茶素。在人工十二指肠液存在的情况下，黄烷-3-醇发生差向异构化。槲皮素完全转化为根皮酚、3,4-二羟基苯甲酸和 2,4,6-三羟基苯甲酸。还观察到羟基肉桂酸酯及其相应的甲酯的同型产物的形成，并且在用大鼠肝细胞孵育时也获得了类似的结果。在肝细胞样品中鉴定出两种根皮素 O-葡萄糖醛酸苷和八种（甲基）槲皮素 O-葡萄糖醛酸苷的Ⅱ相代谢产物。经酶水解后，在血清和尿液中均回收了 5-咖啡酰奎宁酸、4-对香豆酰奎宁酸、咖啡酸、(-)-表儿茶素、根皮苷和槲皮素（分别为消耗量的 5.3%和 3.5%）。此外，在尿液中以羟基化酚和马尿酸的形式鉴定出消耗的多酚类化合物的 19.5%。
这些关于体内多酚类化合物吸收、代谢和全身可用性的发现，有助于我们理解它们的生物学效应，而新形成的代谢物的特征描述应有助于进一步的研究。
