HPLC analysis of chlorogenic acid lactones in roasted coffee

The identification of 3- (3-CQL) and 4-caffeoylquinic acid-γ-lactone (4-CQL) in roasted coffee is described. The lactones were separated from chlorogenic acids (CQA) by an isocratic reversed-phase (RP)-HPLC system and identified as caffeic acid derivatives using their ultraviolet spectra obtained on the fly with an diode array detector. Thermospray liquid-chromatography mass-spectrometry spectra (discharge ionisation, buffer ionisation) showed the quasi molecule ion and characteristic fragments (e.g. caffeic acid, quinide). The lactones were isolated from coffee by polyamide column chromatography followed by RP-HPLC on a semipreparative scale, and structures assigned using Fourier-transform infrared spectroscopy and various nuclear magnetic resonance techniques. There seems to be an equilibrium between the two lactones: isolation of 3-CQL and 4-CQL under the experimental conditions used yielded both lactones in the final product. The content of the caffeoylquinides in commercial coffee samples ranged from 1.5 to 3.5 g/kg dry matter.