Stability and degradation mechanism of (−)-epicatechin in thermal processing

(-)-Epicatechin (EC) is a commonly dietary phytochemical that presents multi-physiological activities on human health. Thermal processing is a common method to extract EC, albeit likely to degrade EC considering its thermal instability. In this study, an 85-min non-durable bathing incubation assay was designed to simulate the state of EC in boiling water while cooking. Monitoring of degradation products was performed using ultra-performance liquid chromatography combined with electrospray ionization quadrupole tandem mass spectrometric detection (UPLC-ESI-TSQ-MS/MS). The results revealed that ca. 65.2 % loss of EC was detected in the first 10 min, and over 99.5 % of EC was degraded within 30 min. A total of 22 degradation products were identified based on retention time, full and tandem MS data were the first to be comprehensively reported. Isomerization, oxidation, hydroxylation, dimerization, and ring cleavage were the main chemical reactions that occurred for EC in boiling aqueous solution.