Characterization of caffeoylquinic acids from Hedyotis diffusa by liquid chromatography/ tandem mass spectrometry

A high-performance liquid chromatography-UV/DAD combined with electrospray ionization tandem mass spectrometry method (HPLC-UV/DAD-ESI-MS/MS) was described for the characterization of caffeoylquinic acids from Hedyotis diffusa. The optimized separation and ionization efficiency for the compounds studied was obtained when using CH3OH/H2O eluent system with 0.1% formic acid as the additive. In this work, three isomers of caffeoylquinic acids, to our knowledge, were observed from Hedyotis diffusa for the first time. Based on the UV spectra and fragmentation of the three isomers in positive and negative ion modes and compared with literatures, they were tentatively identified as 3-O-caffeoylquinic acid, 5-O-caffeoylquinic acid and 4-O-caffeoylquinic acid, respectively.