Profile and Characterization of the Chlorogenic Acids in Green Robusta Coffee Beans by LC-MSn: Identification of Seven New Classes of Compounds

Abstract

LC-MS(n) (n = 2-4) has been used to detect and characterize in green Robusta coffee beans 15 quantitatively minor sinapic acid and trimethoxycinnamoylquinic acid-containing chlorogenic acids, all reported for the first time from this source, with 13 of them not previously reported in nature. These comprise 3-sinapoylquinic acid, 4-sinapoylquinic acid, and 5-sinapoylquinic acid (M(r) 398); 3-sinapoyl-5-caffeoylquinic acid, 3-sinapoyl-4-caffeoylquinic acid, and 4-sinapoyl-3-caffeoylquinic acid (M(r) 560); 3-(3,5-dihydroxy-4-methoxy)cinnamoyl-4-feruloylquinic acid (M(r) 560); 3-sinapoyl-5-feruloylquinic acid, 3-feruloyl-4-sinapoylquinic acid, and 4-sinapoyl-5-feruloylquinic acid (M(r) 574); 4-trimethoxycinnamoyl-5-caffeoylquinic acid, 3-trimethoxycinnamoyl-5-caffeoylquinic acid (M(r) 574); and 5-feruloyl-3-trimethoxycinnamoylquinic acid, 3-trimethoxycinnamoyl-4-feruloylquinic acid, and 4-trimethoxycinnamoyl-5-feruloylquinic acid (M(r) 588). Furthermore, a series of structures including nine new triacyl quinic acids have been assigned on the basis of LC-MS(n) patterns of fragmentation, relative hydrophobicity, and analogy of fragmentation patterns if compared to feruloyl, caffeoyl, and dimethoxycinnamoyl quinic acids. Sixty-nine chlorogenic acids have now been characterized in green Robusta coffee beans.