Osman A M, Wong K K Y, Fernyhough A
Scion, Private Bag 3020, Rotorua, New Zealand.
Biochem Biophys Res Commun. 2006 Jul 21;346(1):321-9. doi: 10.1016/j.bbrc.2006.05.118. Epub 2006 May 30.
The formation of covalent adducts obtained from the reaction of the polyphenols, trans-3,3',4',5,7-pentahydroxyflavan (catechin) and 1,3,5-trihydroxybenzene (phloroglucinol), with ABTS radicals is reported. Two adducts derived from (+)-catechin and three adducts from phloroglucinol were isolated and identified using reversed-phase high performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS). The molecular masses of the (+)-catechin-derived adducts (I(c) and II(c)) were found to be 802 and 559 Da, respectively, whereas the masses of phloroglucinol-derived adducts (I(p), II(p), and III(p)) were 638, 395, and 381 Da, respectively. The initially formed adducts (I(c), I(p)) were unstable and degraded to secondary adducts (II(c), II(p), and III(p)) releasing part of the ABTS molecule. The structures of these adducts were elucidated by interpreting the results of MS/MS analysis of prominent ions generated by both positive and negative ion ESI-MS. The adducts were found to scavenge ABTS radicals, an observation that could explain the complex kinetic behaviour manifested by the reactions of ABTS radicals with polyphenols. A mechanism, which accounts for both the formation of the adducts and the degradation products of ABTS radicals, is proposed.
本文报道了多酚类物质反式 - 3,3',4',5,7 - 五羟基黄烷（儿茶素）和1,3,5 - 三羟基苯（间苯三酚）与ABTS自由基反应生成的共价加合物。使用反相高效液相色谱（HPLC）和电喷雾电离质谱（ESI - MS）分离并鉴定了两种源自（+） - 儿茶素的加合物和三种源自间苯三酚的加合物。发现源自（+） - 儿茶素的加合物（I(c)和II(c)）的分子量分别为802和559 Da，而源自间苯三酚的加合物（I(p)、II(p)和III(p)）的分子量分别为638、395和381 Da。最初形成的加合物（I(c)、I(p)）不稳定，会降解为二级加合物（II(c)、II(p)和III(p)），同时释放出部分ABTS分子。通过解释正负离子ESI - MS产生的主要离子的MS/MS分析结果，阐明了这些加合物的结构。发现这些加合物能够清除ABTS自由基，这一观察结果可以解释ABTS自由基与多酚反应所表现出的复杂动力学行为。本文提出了一种机制，该机制解释了加合物的形成以及ABTS自由基的降解产物。
