[Spectroscopic and structural characteristics of the main components of Theabrownin in Pu-erh tea].
In the present study, we fractionated the main components of TB in Pu-erh tea by dialysis and investigated their compositions, structures and properties. TB in the Pu-erh tea was fractionated by dialyses using films with different pore sizes. The highest TB concentration was obtained in the fraction with molecular weight species > 25 000 Da. The carboxyl and hydroxyl concentrations also increased in fractions where the molecular weight size selection was highest (i. e. , > 25 000 Da). AFM images revealed that TB particles with different molecular weights had different morphologies and the TB particles appeared as scattered islands or aggregates. CP-MAS NMR experiments revealed that the TB fraction with molecular weight species between 3 500 and 25 000 Da in size was characterized by a polymeric material of polyphenols. This polymeric substance contained primarily multiple benzene rings, polysaccharides, protein residue groups and various other functional groups. After acidic hydrolysis, this fraction formed a black precipitate. CP-MAS NMR found that the precipitate was a polymeric material with multiple benzene rings. CP-GC/MS identified 16 candidate compounds from the pyrolysis products of the black precipitate obtained from the main fraction with molecular weight species between 3 500 and 25 000 Da.
Faculty of Food Science and Technology, Yunnan Agricultural University, Kunming 650201, China. tctj_1212@163.com
Chao
C
Tan
Chun-xiu
CX
Peng
Bin
B
Gao
Jia-shun
JS
Gong
D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D009682:Magnetic Resonance Spectroscopy; D010936:Plant Extracts; D059808:Polyphenols / Q000737:chemistry*; D013057:Spectrum Analysis; D013662:Tea / Q000737:chemistry*
D010936:Plant Extracts; D059808:Polyphenols; D013662:Tea; C569455:theabrownin; D002392:Catechin