Absorption, metabolism and health effects of dietary flavonoids in man
Absorption, metabolism and health effects of dietary flavonoids in man
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DOI：
10.1016/s0753-3322(97)88045-6
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发表时间：
1997-01-01
影响因子：
7.5
通讯作者：
Katan, MB
中科院分区：
文献类型：
--
作者：
Hollman, PCH;Katan, MB
黄酮类化合物是多酚类化合物，普遍存在于植物源性食品中。已经描述了超过4，000种不同的类黄酮，并且它们被分类为黄酮醇、黄酮、儿茶素、黄烷酮、花青素和花青素。黄酮类化合物在许多哺乳动物细胞系统中具有多种生物学效应，无论是体外还是体内。近年来，在动物研究中，它们的抗氧化特性及其在肿瘤发展的各个阶段中的抑制作用受到了广泛关注。槲皮素是黄酮醇亚类的主要代表，是一种强抗氧化剂，在体外可防止低密度脂蛋白的氧化。氧化型低密度脂蛋白是致动脉粥样硬化的，并且被认为是动脉粥样硬化斑块形成的关键中间体。这与流行病学研究中的观察结果一致，即黄酮醇和黄酮的摄入与随后的冠心病呈负相关。然而，在这些研究中没有发现黄酮醇对癌症的影响。类黄酮的吸收程度是一个重要的未解决的问题，在判断他们的许多所谓的健康影响。食物中存在的风味物质被认为是不可吸收的，因为它们与糖结合为β-糖苷。只有没有糖分子的游离类黄酮，即所谓的糖苷配基，被认为能够穿过肠壁。水解仅发生在结肠中的微生物，在同一时间降解类黄酮。我们进行了一项研究，以量化各种饮食形式的槲皮素的吸收。令我们惊讶的是，洋葱中的槲皮素糖苷比纯糖苷配基更容易被吸收。随后的药代动力学研究与饮食槲皮素糖苷显示吸收率和生物利用度显着差异。吸收的槲皮素仅缓慢地从血液中消除。黄酮类化合物的代谢经常在各种动物中进行研究，但在人类中的数据很少。类黄酮代谢的两个主要部位是肝脏和结肠植物群。有证据表明肝脏中羟基的O-甲基化、硫酸化和葡萄糖醛酸化。类黄酮的细菌环分裂发生在结肠中。随后的降解产物，酚酸，可以被吸收，并在动物的尿液中发现。关于新陈代谢的定量数据很少。
Flavonoids are polyphenolic compounds that occur ubiquitously in foods of plant origin. Over 4,000 different flavonoids have been described, and they are categorized into flavonols, flavones, catechins, flavanones, anthocyanidins and isoflavonoids. Flavonoids have a variety of biological effects in numerous mammalian cell systems, in vitro as well in vivo. Recently, much attention has been paid to their antioxidant properties and to their inhibitory role in various stages of tumour development in animal studies. Quercetin, the major representative of the flavonol subclass, is a strong antioxidant, and prevents oxidation of low density lipoproteins in vitro. Oxidized low density lipoproteins are atherogenic, and are considered to be a crucial intermediate in the formation of atherosclerotic plaques. This agrees with observations in epidemiological studies that the intake of flavonols and flavones was inversely associated with subsequent coronary heart disease. However, no effects of flavonols on cancer were found in these studies. The extent of absorption of flavonoids is an important unsolved problem in judging their many alleged health effects. Flavonoids present in foods were considered non-absorbable because they are bound to sugars as beta-glycosides. Only free flavonoids without a sugar molecule, the so-called aglycones, were thought to be able to pass through the gut wall. Hydrolysis only occurs in the colon by microorganisms, which at the same lime degrade flavonoids. We performed a study to quantify absorption of various dietary forms of quercetin. To our surprise, the quercetin glycosides from onions were absorbed far better than the pure aglycone. Subsequent pharmacokinetic studies with dietary quercetin glycosides showed marked differences in absorption rate and bioavailability. Absorbed quercetin was eliminated only slowly from the blood. The metabolism of flavonoids has been studied frequently in various animals, bur very few data in humans are available. Two major sites of flavonoid metabolism are the liver and the colonic flora. There is evidence for O-methylation, sulphation and glucuronidation of hydroxyl groups in the liver. Bacterial ring fission of flavonoids occurs in the colon. The subsequent degradation products, phenolic acids, can be absorbed and are found in urine of animals. Quantitative data on metabolism are scarce.