Linus Pauling Institute, Oregon State University, Corvallis, OR 97331, USA.
Free Radic Biol Med. 2011 Jul 15;51(2):454-63. doi: 10.1016/j.freeradbiomed.2011.04.032. Epub 2011 Apr 22.
The notion that dietary flavonoids exert beneficial health effects in humans is often based on in vitro studies using the glycoside or aglycone forms of these flavonoids. However, flavonoids are extensively metabolized in humans, resulting in the formation of glucuronide, methyl, and sulfate derivatives, which may have different properties than their parent compounds. The goal of this study was to investigate whether different chemical modifications of the same flavonoid molecule affect its biological and antioxidant activities. Hence, we studied the anti-inflammatory effects of several major human metabolites of quercetin and (-)-epigallocatechin-3-O-gallate (EGCG) by assessing their inhibitory effects on tumor necrosis factor α (TNFα)-induced protein expression of cellular adhesion molecules in human aortic endothelial cells (HAEC). HAEC were incubated with 1-30 μM quercetin, 3'- or 4'-O-methyl-quercetin, quercetin-3-O-glucuronide, and quercetin-3'-O-sulfate or 20-100 μM EGCG, 4''-O-methyl-EGCG, and 4',4''-di-O-methyl-EGCG, prior to coincubation with 100 U/ml of TNFα. 3'-O-Methyl-quercetin, 4'-O-methyl-quercetin, and their parent aglycone compound, quercetin, all effectively inhibited expression of intercellular adhesion molecule-1 (ICAM-1) with IC(50) values (concentration required for 50% inhibition) of 8.0, 5.0, and 4.4 μM, respectively; E-selectin expression was suppressed to a somewhat lesser but still significant degree by all three compounds, whereas vascular cell adhesion molecule-1 (VCAM-1) was not affected. In contrast, quercetin-3-O-glucuronide (20-100 μM), quercetin-3'-O-sulfate (10-30 μM), and phenolic acid metabolites of quercetin (20-100 μM) did not inhibit adhesion molecule expression. 4',4''-Di-O-methyl-EGCG selectively inhibited ICAM-1 expression with an IC(50) value of 94 μM, whereas EGCG (20-60 μM) and 4''-O-methyl-EGCG (20-100 μM) had no effect. The inhibitory effects of 3'-O-methyl-quercetin and 4',4''-di-O-methyl-EGCG on adhesion molecule expression were not related either to inhibition of NF-κB activation or to their antioxidant reducing capacity. Our data indicate that flavonoid metabolites have different biological and antioxidant properties than their parent compounds, and suggest that data from in vitro studies using nonmetabolites of flavonoids are of limited relevance in vivo.
认为膳食类黄酮在人类中发挥有益健康的作用，这通常基于使用这些类黄酮的糖苷或苷元形式的体外研究。然而，类黄酮在人体内广泛代谢，形成葡萄糖醛酸、甲基和硫酸盐衍生物，它们的性质可能与母体化合物不同。本研究的目的是探讨同一类黄酮分子的不同化学修饰是否会影响其生物学和抗氧化活性。因此，我们通过评估它们对人主动脉内皮细胞（HAEC）中肿瘤坏死因子 α（TNFα）诱导的细胞间黏附分子蛋白表达的抑制作用，研究了槲皮素和（-）-表没食子儿茶素-3-O-没食子酸酯（EGCG）的几种主要人体代谢物的抗炎作用。HAEC 在用 1-30 μM 槲皮素、3'-或 4'-O-甲基槲皮素、槲皮素-3-O-葡萄糖醛酸苷和槲皮素-3'-O-硫酸盐或 20-100 μM EGCG、4''-O-甲基-EGCG 和 4'，4''-二-O-甲基-EGCG 孵育后，与 100 U/ml TNFα 共孵育。3'-O-甲基槲皮素、4'-O-甲基槲皮素及其母体苷元化合物槲皮素均有效抑制细胞间黏附分子-1（ICAM-1）的表达，IC50 值（抑制 50%所需的浓度）分别为 8.0、5.0 和 4.4 μM；所有三种化合物均能抑制选择素的表达，但程度较低，但仍具有显著意义，而血管细胞黏附分子-1（VCAM-1）不受影响。相比之下，槲皮素-3-O-葡萄糖醛酸苷（20-100 μM）、槲皮素-3'-O-硫酸盐（10-30 μM）和槲皮素的酚酸代谢物（20-100 μM）均不能抑制黏附分子的表达。4'，4''-二-O-甲基-EGCG 对 ICAM-1 表达的抑制作用具有选择性，IC50 值为 94 μM，而 EGCG（20-60 μM）和 4''-O-甲基-EGCG（20-100 μM）则没有影响。3'-O-甲基槲皮素和 4'，4''-二-O-甲基-EGCG 对黏附分子表达的抑制作用与 NF-κB 激活的抑制或其抗氧化还原能力无关。我们的数据表明，类黄酮代谢物具有与母体化合物不同的生物学和抗氧化特性，并表明使用类黄酮非代谢物进行体外研究的数据在体内相关性有限。
