Hierarchical scheme for LC-MSn identification of chlorogenic acids
Hierarchical scheme for LC-MSn identification of chlorogenic acids
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DOI：
10.1021/jf026187q
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发表时间：
2003-05-07
影响因子：
6.1
通讯作者：
Kuhnert, N
中科院分区：
文献类型：
--
作者：
Clifford, MN;Johnston, KL;Kuhnert, N
使用LC-MS 4应用于甲醇咖啡豆提取物和商业苹果酒（硬苹果酒）的18个绿原酸，在位置1处未被取代的裂解行为进行了研究。使用LC-MS 3，可以区分对香豆酰奎尼酸、咖啡酰奎尼酸、阿魏酰奎尼酸和二咖啡酰奎尼酸的三种异构体中的每一种，并且当标准品不可用时，已经制备了分级键以促进该过程。MS 4片段化进一步支持这些分配，但不是达到它们所必需的。与5-酰基绿原酸相比，4-酰基和3-酰基绿原酸的独特行为是允许这些分配的关键因素。断裂模式取决于奎尼酸部分上的各个取代基之间的特定立体化学关系。碎片是促进1，2-酰基参与和收益通过奎尼酸构象，其中相关的取代基瞬时通过1，3-顺-双轴关系。在m/z 529处的选择离子监测清楚地表明咖啡中存在六种咖啡酰阿魏酰奎宁酸异构体，而以前只有两种或三种被证明。分级索引允许将特定结构分配给六种异构体中的每一种。这些分配是内部一致的，并与以前可用的有限数据相一致。
The fragmentation behavior of 18 chlorogenic acids that are not substituted at position 1 has been investigated using LC-MS4 applied to a methanolic coffee bean extract and commercial cider (hard cider). Using LC-MS3, it is possible to discriminate between each of the three isomers of p-coumaroylquinic acid, caffeoylquinic acid, feruloylquinic acid, and dicaffeoylquinic acid, and a hierarchical key has been prepared to facilitate this process when standards are not available. MS4 fragmentations further support these assignments, but were not essential in reaching them. The distinctive behavior of 4-acyl and 3-acyl chlorogenic acids compared with the 5-acyl chlorogenic acids is a key factor permitting these assignments. The fragmentation patterns are dependent upon the particular stereochemical relationships between the individual substituents on the quinic acid moiety. Fragmentation is facilitated by 1,2-acyl participation and proceeds through quinic acid conformers in which the relevant substituents transiently adopt a 1,3-syn-diaxial relationship. Selected ion monitoring at m/z 529 clearly indicated the presence in coffee of six caffeoylferuloylquinic acid isomers, whereas previously only two or three had been demonstrated. The hierarchical key permitted specific structures to be assigned to each of the six isomers. These assignments are internally consistent and consistent with the limited data previously available.