Novel Oxidation Oligomer of Chlorogenic Acid and (−)-Epigallocatechin and Its Quantitative Analysis during the Processing of Keemun Black Tea

Abstract

Not only do flavan-3-ols participate in the formation of chromogenic oxidation products such as theaflavins, but chlorogenic acid (3-caffeoylquinic acid, CQA) is also involved in the enzymatic oxidation during black tea processing. The critical oxidation product of CQA and (−)-epigallocatechin (EGC) were identified as an adduct containing benzobicyclo[3.2.2]nonenone structure, which was named as the dichlorogeniccatechin (DCGC) oligomer. It was composed of two molecules of CQA and one molecule of EGC. The effects of the initial reactant ratio and reaction time on the generation of DCGC were also analyzed. A high proportion of CQA promoted the production of DCGC, but a high proportion of EGC inhibited the DCGC formation. In addition, the content of DCGC in Keemun black tea during processing was determined. The content of DCGC highly increased after withering but decreased after drying. This study provides a new perspective for the investigation of other oxidation oligomers in black tea.

Screening and identification of an aflatoxin B1-degrading strain from the Qinghai-Tibet Plateau and biodegradation products analysis

“…Samples were injected and eluted using a mobile solvent containing mobile phase A, which was an aqueous solution containing 0.1% formic acid and 5 mmol/L ammonium formate, and mobile phase B, a methanol solution containing 0.1% formic acid and 5 mmol/L ammonium formate. The mass spectrometry parameters were set similar to that in previous study ( Lai et al, 2023 ).…”