Identification of proline-based diketopiperazines in roasted coffee

Area of Science:

• Food Chemistry
• Analytical Chemistry
• Organic Chemistry

Background:

• Diketopiperazines (DKPs) are cyclic dipeptides with potential biological activities.
• Roasted coffee is a complex matrix containing numerous flavor and aroma compounds.
• Understanding the chemical composition of coffee is crucial for quality assessment and product development.

Purpose of the Study:

• To identify and characterize proline-based diketopiperazines in roasted coffee.
• To confirm the presence of these compounds in both roasted coffee and its water extracts.

Main Methods:

• Isolation techniques including gel chromatography and solvent extraction (CHCl(3)).
• Polyamide column chromatography for roasted coffee brews.
• Identification using Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (LC-ESI-MS) and MS/MS.
• Confirmation using Gas Chromatography-Electron Ionization-Mass Spectrometry (GC-EI-MS).

Main Results:

• Five specific proline-based diketopiperazines were identified: cyclo(pro-ile), cyclo(pro-leu), cyclo(pro-phe), cyclo(pro-pro), and cyclo(pro-val).
• The presence of these diketopiperazines was unambiguously verified in roasted coffee extracts and brews.
• LC-ESI-MS/MS and GC-EI-MS provided consistent identification based on retention times and fragmentation patterns.

Conclusions:

• Proline-based diketopiperazines are naturally occurring compounds in roasted coffee.
• The applied analytical methods (LC-ESI-MS/MS and GC-EI-MS) are suitable for the unambiguous identification of these compounds.
• This finding contributes to the understanding of the chemical profile of roasted coffee.