Quantitative analysis of N-phenylpropenoyl-L-amino acids in roasted coffee and cocoa powder by means of a stable isotope dilution assay

Timo Stark, Helene Justus, Thomas Hofmann

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

Since recent reports on the role of N-phenylpropenoyl-L-amino acids as powerful antioxidants and key contributors to the astringent taste of cocoa nibs, there is an increasing interest in the concentrations of these phytochemicals in plant-derived foods. A versatile analytical method for the accurate quantitative analysis of N-phenylpropenoyl-L-amino acids in plant-derived foods by means of HPLC-MS/MS and synthetic stable isotope labeled N-phenylpropenoyl-L-amino acids as internal standards was developed. By means of the developed stable isotope dilution assay (SIDA), showing recovery rates of 95-102%, 14 N-phenylpropenoyl-L-amino acids were quantified for the first time in cocoa and coffee samples. On the basis of the results of LC-MS/MS experiments as well as cochromatography with the synthetic reference compounds N-[3′,4′-dihydroxy-(E)-cinnamoyl]-L-tryptophan, N-[4′-hydroxy- (E)-cinnamoyl]-L-tryptophan, and N-[4′-hydroxy-3′-methoxy-(E)- cinnamoyl]-L-tyrosine, respectively, were detected for the first time in cocoa powder, and (-)-N-[4′-hydroxy-(E)-cinnamoyl]-L-tyrosine, (-)-N-[3′,4′-dihydroxy-(E)-cinnamoyl]-L-tyrosine, N-[4′-hydroxy-3′-methoxy-(E)-cinnamoyl]-L-tyrosine, (+)-N-[3′,4′-dihydroxy-(E)-cinnamoyl]-L-aspartic acid, (+)-N-[4′-hydroxy-(E)-cinnamoyl]-L-aspartic acid, N-[3′,4′- dihydroxy-(E)-cinnamoyl]-L-tryptophan, N-[4′-hydroxy-(E)-cinnamoyl]-L- tryptophan, and N-[4′-hydroxy-3′-methoxy-(E)-cinnamoyl]-L- tryptophan, respectively, were detected for the first time in coffee beverages.

Original languageEnglish
Pages (from-to)2859-2867
Number of pages9
JournalJournal of agricultural and food chemistry
Volume54
Issue number8
DOIs
StatePublished - 19 Apr 2006
Externally publishedYes

Keywords

  • Cocoa
  • Coffee
  • N-[3′,4′-dihydroxy-(E)-cinnamoyl]-L-aspartic acid
  • N-phenylpropenoyl-L-amino acids
  • SIDA
  • Stable isotope dilution assay
  • Taste

Fingerprint

Dive into the research topics of 'Quantitative analysis of N-phenylpropenoyl-L-amino acids in roasted coffee and cocoa powder by means of a stable isotope dilution assay'. Together they form a unique fingerprint.

Cite this