In this study, liquid chromatography-tandem mass spectrometry (LC-MS(n); n = 2-3) has been used to characterize and distinguish chlorogenic acid lactones from cinnamoylshikimate esters. This is the first time when an LC-MS(n) method has been developed to distinguish between these two isomeric classes of compounds formed in particular in food processing from chlorogenic acids at elevated temperature through loss of water. The structures of regioisomeric chlorogenic acid lactones and shikimate esters have been assigned on the basis of LC-MS(n) patterns of fragmentation, relative hydrophobicity, and fragmentation analogy with the synthetic standards of dimethoxycinnamic, ferulic, and caffeic acid containing monoacyl chlorogenic acid lactones and shikimate esters.
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