期刊
SCIENTIFIC REPORTS
卷 5, 期 -, 页码 -出版社
NATURE RESEARCH
DOI: 10.1038/srep08742
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资金
- Natural Science Foundation of China [31170647, 31470689, 31270730, 31300577, 31200229]
- Specialized Research Fund for the Doctoral Program of Higher Education [20133418130001]
- Natural Science Foundation of Anhui Province, China [1408085QC51]
- Special Foundation for Indepenent Innovation of Anhui Province, China [13Z03012]
- Biology Key Subject Construction of Anhui
In the present study, proanthocyanidins were qualitatively and quantitatively identified using hydrolysis and thiolysis assays, NP-HPLC, HPLC-ESI-MS, MALDI-TOF-MS, H-1-NMR, and C-13-NMR techniques in different organs of tea plants. The results showed that in leaves, the tri-hydroxyl, cis-and galloylated flavan-3-ols were the main monomeric catechins units, and (epi) catechin was found to be the major unit of polymeric flavan-3-ols when the degree of polymerization was greater than five. In roots, the PAs were found to be abundant, and epicatechin formed the predominant extension unit of oligomeric and polymeric PAs. In order to understand the mechanism of proanthocyanidins polymerization, auto-condensation of the flavan-3-ols was investigated. The results showed that the same trimers (m/z 865) were detected in the extracts of tea plants and in the non-enzymatic in vitro assay, in weak acid as well as weak alkaline solutions at room temperature, when the substrates used were either procyanidin B2 and monomeric flavan-3-ols (epicatechin or catechin), or only procyanidin B2. This suggested that procyanidin B2 not only released carbocation as electrophilic upper units, but also could be used as nucleophilic lower units directly itself, to form the procyanidin trimer in vitro or in vivo.
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