Characterization by LC-MSn of four new classes of p-coumaric acid-containing diacyl chlorogenic acids in green coffee beans

LC-MS4 has been used to detect and characterize in green coffee beans 15 quantitatively minor p-coumaric acid-containing chlorogenic acids not previously reported in nature. These comprise 3,4-di- p-coumaroylquinic acid, 3,5-di-p-coumaroylquinic acid, and 4,5-di-p-coumaroylquinic acid (M-r 484); 3-p-coumaroyl-4-caffeoylquinic acid, 3-p-coumaroyl-5-caffeoylquinic acid, 4-p-coumaroyl-5-caffeoylquinic acid, 3-caffeoyl-4-p-coumaroyl-quinic acid, 3-caffeoyl-5-p-coumaroyl-quinic acid; and 4-caffeoyl-5-p-coumaroyl-quinic acid (M-r 500); 3-p-coumaroyl-4-feruloylquinic acid, 3-p-coumaroyl-5- feruloylquinic acid and 4-p-coumaroyl-5-feruloylquinic acid (M-r 514); and 4- dimethoxycinnamoyl-5-p-coumaroylquinic acid and two isomers (M-r 528) for which identities could not be assigned unequivocally. Structures have been assigned on the basis of LC-MS4 patterns of fragmentation. Forty-five chlorogenic acids have now been characterized in green Robusta coffee beans.