Catechin degradation and concurrent formation of homo‐ and hetero‐ catechin dimers during simulated digestion

Several in vitro experiments have shown catechins to be instable in solutions of near‐neutral pH. Reported epigallocatechin gallate (EGCG) degradation products are homodimers, including C6′‐C6′ dimers (theasinensins) and B‐ring condensation dimers. However, limited data exists on catechin degradation products under digestive conditions. The objective of this study was to characterize digestive stability and degradation products of EGCG, epigallocatechin (EGC), epicatechin gallate (ECG), epicatechin (EC), and catechin (C), individually and in combination, by simulated gastric and small intestinal digestion. HPLC analysis of individual catechin digesta indicated digestive losses of 91, 72, 60, 11, and 7% (EGCG, EGC, ECG, EC, and C, respectively). Catechin degradation products were characterized by LC‐MS/MS. EGCG digesta contained two previously reported homodimers, theasinensin (m/z 913) and a condensation dimer (m/z 883); EGC digesta contained two homodimers (m/z 579, 609) from analogous reactions. EGCG/EGC combined digesta contained the four EGCG and EGC homodimers as well as EGCG/EGC C6′‐C6′ (m/z 761) and B‐ring condensation (m/z 731) heterodimers. Multiple dimers of identical MS/MS spectra were observed in EGC digesta, suggesting potential epimerization to gallocatechin (GC), yielding various stereoisomeric forms of each EGC homodimer. Observation of these previously unreported dimers in vitro suggests potential formation in vivo. (Supported by NIH grant CA119210‐01A1).