School of Food Science and Nutrition, University of Leeds, LS29JT Leeds, UK.
J Nutr Biochem. 2010 Nov;21(11):1060-8. doi: 10.1016/j.jnutbio.2009.09.001. Epub 2009 Dec 1.
Hydroxycinnamic acids are a class of phenolic antioxidants found widely in dietary plants. Their biotransformation in the human organism primarily involves Phase II conjugation reactions. In this study, activities of UDP-glucuronosyltransferases (UGTs) and sulfotransferases (SULTs) towards major dietary hydroxycinnamic acids (caffeic, dihydrocaffeic, dihydroferulic, ferulic and isoferulic acids) were investigated. Conjugate formation was evaluated using human liver and intestinal S9 homogenates, and in vitro characterization was carried out using recombinant human UGTs and SULTs. Analysis of the kinetics of hydroxycinnamic acid conjugation in human S9 homogenates revealed that intrinsic clearance (V(max)/K(m)) is much greater for sulfation than for glucuronidation. Assessment of activity using a panel of recombinant human SULTs showed that SULT1A1 is most active in the sulfation of caffeic, dihydrocaffeic and isoferulic acids, while SULT1E1 is most active in the sulfation of ferulic and dihydroferulic acids. Only isoferulic acid was significantly glucuronidated by human liver S9 homogenates, explained by the high activity of liver-specific UGT1A9. Studies on the kinetics of active SULTs and UGTs demonstrated a markedly lower K(m) for SULTs. To further corroborate our findings, we carried out an intervention study in healthy humans to determine the hydroxycinnamic acid conjugates in urine after consumption of hydroxycinnamate-rich coffee (200 ml). Analysis showed that sulfates are the main conjugates in urine, with the exception of isoferulic acid, which is mainly glucuronidated. These data suggest that sulfates are the predominant hydroxycinnamic acid conjugates in humans, and that SULT mediated sulfation is a major factor determining the bioavailability of hydroxycinnamic acids in vivo.
羟基肉桂酸是一类广泛存在于膳食植物中的酚类抗氧化剂。它们在人体中的生物转化主要涉及Ⅱ相共轭反应。在这项研究中，研究了 UDP-葡糖醛酸基转移酶（UGTs）和磺基转移酶（SULTs）对主要膳食羟基肉桂酸（咖啡酸、二氢咖啡酸、二氢阿魏酸、阿魏酸和异阿魏酸）的活性。通过人肝和肠 S9 匀浆评估了结合物的形成，并使用重组人 UGTs 和 SULTs 进行了体外特性分析。在人 S9 匀浆中对羟基肉桂酸结合的动力学分析表明，磺化的内在清除率（V(max)/K(m)）远大于葡糖醛酸化。使用一组重组人 SULTs 评估活性表明，SULT1A1 在咖啡酸、二氢咖啡酸和异阿魏酸的磺化中最活跃，而 SULT1E1 在阿魏酸和二氢阿魏酸的磺化中最活跃。只有异阿魏酸被人肝 S9 匀浆显著葡糖醛酸化，这可以用肝特异性 UGT1A9 的高活性来解释。对活性 SULT 和 UGT 的动力学研究表明，SULT 的 K(m)明显较低。为了进一步证实我们的发现，我们在健康人中进行了一项干预研究，以确定摄入富含羟基肉桂酸的咖啡（200 毫升）后尿液中的羟基肉桂酸结合物。分析表明，除了主要葡糖醛酸化的异阿魏酸外，硫酸盐是尿液中的主要结合物。这些数据表明，硫酸盐是人体中主要的羟基肉桂酸结合物，而 SULT 介导的磺化是决定体内羟基肉桂酸生物利用度的主要因素。
