Chlorogenic acid-arabinose hybrid domains in coffee melanoidins: Evidences from a model system

Abstract

Arabinose from arabinogalactan side chains was hypothesized as a possible binding site for chlorogenic acids in coffee melanoidins. To investigate this hypothesis, a mixture of 5 O caffeoylquinic acid (5 CQA), the most abundant chlorogenic acid in green coffee beans, and (a1?5) L arabinotriose, structurally related to arabinogalactan side chains, was submitted to dry thermal treatments. The compounds formed during thermal processing were identified by electrospray ionization mass spectrometry (ESI MS) and characterized by tandem MS (ESI MSn). Compounds composed by one or two CQAs covalently linked with pentose (Pent) residues (1 12) were identified, along with compounds bearing a sugar moiety but composed exclusively by the quinic or caffeic acid moiety of CQAs. The presence of isomers was demonstrated by liquid chromatography online coupled to ESI MS and ESI MSn. Pent1 2CQA were identified in coffee samples. These results give evidence for a diversity of chlorogenic acid arabinose hybrids formed during roasting, opening new perspectives for their identification in melanoidin structures.