The cinnamoyl–amino acid conjugates of green robusta coffee beans

Methanolic extracts of green robusta coffee beans have been analysed for cinnamoyl amides by electrospray LC–MSn. Evidence is presented for the presence of p-coumaroyl-N-tyrosine, feruloyl-N-tyrosine, feruloyl-N-tryptophan and caffeoyl-N-phenylalanine, in addition to the previously reported p-coumaroyl-N-tryptophan, caffeoyl-N-tryptophan and caffeoyl-N-tyrosine. These compounds are found at higher levels in Angolan coffees compared with coffees of other origins. Caffeoyl-N-phenylalanine has previously been reported in Lady Fern (Athyrium filix-femina) but p-coumaroyl-N-tyrosine, feruloyl-N-tyrosine and feruloyl-N-tryptophan seem not to have been reported elsewhere. A combination of negative ion and positive ion LC–MS2 is a convenient procedure for characterising cinnamoyl amides as the former gives an MS2 base peak defining the amino acid and the latter an MS2 base peak defining the cinnamic acid in the conjugate.