Hierarchical scheme for liquid chromatography/multi‐stage spectrometric identification of 3,4,5‐triacyl chlorogenic acids in green Robusta coffee beans

Abstract

Liquid chromatography/multi-stage spectrometry (LC/MS(n)) (n = 2-4) has been used to detect and characterize in green Robusta coffee beans eight quantitatively minor triacyl chlorogenic acids with seven of them not previously reported in nature. These comprise 3,4,5-tricaffeoylquinic acid (Mr 678); 3,5-dicaffeoyl-4-feruloylquinic acid, 3-feruloyl-4,5-dicaffeoylquinic acid and 3,4-dicaffeoyl-5-feruloylquinic acid (Mr 692); 3-caffeoyl-4,5-diferuloylquinic acid and 3,4-diferuloyl-5-caffeoylquinic acid (Mr 706); and 3,4-dicaffeoyl-5-sinapoylquinic acid and 3-sinapoyl-4,5-dicaffeoylquinic acid (Mr 722). Structures have been assigned on the basis of LC/MS(n) patterns of fragmentation. A new hierarchical key for the identification of triacyl quinic acids is presented, based on previously established rules of fragmentation. Fifty-two chlorogenic acids have now been characterized in green Robusta coffee beans. In this study five samples of green Robusta coffee beans and fifteen samples of Arabica coffee beans were analyzed with triacyl chlorogenic acids only found in Robusta coffee bean extracts. These triacyl chlorogenic acids could be considered as useful phytochemical markers for the identification of Robusta coffee beans.