Functional Materials and Nanomolecular Science Research Centre, Jacobs University Bremen, 28759 Bremen, Germany.
Food Funct. 2010 Nov;1(2):180-99. doi: 10.1039/c0fo00066c. Epub 2010 Oct 14.
LC-MS(n) and direct infusion-MS(n) have been applied for the first time to the characterisation of crude thearubigins isolated from black tea. The data generated have been used to test two hypotheses of thearubigin structure: (i) that a significant fraction of the thearubigins consist of polyhydroxylated derivatives of the better-known catechin dimers (theaflavins, theaflavin mono- and di-gallates, theacitrins) in redox equilibrium with their associated quinones; and (ii) that a significant fraction of the thearubigins consist of dicarboxylic acids generated by oxidative cleavage of aromatic diols. The data were consistent with the polyhydroxylation hypothesis and did not support the dicarboxylic acid hypothesis. Evidence is presented for the presence in crude thearubigins of at least 29 hydroxylated theaflavins (with between one and six oxygen insertions), at least 12 theaflavin mono-gallates (with between one and six oxygen insertions), at least nine theaflavin di-gallates (with between one and four oxygen insertions), and at least ten theacitrin mono-gallates (with between one and four oxygen insertions). Evidence is also presented for at least ten mono- or di-quinone forms of the parent compounds and hydroxylated derivatives in each of these homologous series. A general method for the analysis of complex mixtures by tandem LC-MS is furthermore introduced and established.
LC-MS(n) 和直接进样-MS(n) 首次被应用于红茶中原儿茶素的结构鉴定。所得数据用于检验儿茶素结构的两个假说：（i）儿茶素的相当一部分是由众所周知的儿茶素二聚体（茶黄素、茶黄素单和双没食子酸酯、茶红素）的多羟基衍生物组成，处于与其相关醌的氧化还原平衡中；（ii）儿茶素的相当一部分是由芳香二醇氧化裂解生成的二羧酸组成。数据与多羟基假说一致，不支持二羧酸假说。研究结果表明，粗儿茶素中至少存在 29 种羟化茶黄素（具有 1 到 6 个氧插入）、至少 12 种茶黄素单没食子酸酯（具有 1 到 6 个氧插入）、至少 9 种茶黄素双没食子酸酯（具有 1 到 4 个氧插入）、至少 10 种茶红素单没食子酸酯（具有 1 到 4 个氧插入）。此外，在这些同源系列中，每种化合物的母体化合物及其羟基化衍生物都至少存在 10 种单或双醌形式。此外，还介绍并建立了一种用于分析复杂混合物的串联 LC-MS 通用方法。
