Carbon-13 CP-MAS nuclear magnetic resonance studies of teas.
13C CP-MAS NMR spectra of green and black tea were obtained and assigned based on the solid-state NMR spectra of tropolone, (+)-catechin hydrate, gallic acid, caffeine and flavone derivatives. The peak shape and chemical shifts observed for carbonyl carbons in CP-MAS spectra of teas indicate the existence of different chemical species, mainly free phenollic acids and ester derivatives of flavonoids. The peak patterns allow to establish differences between both teas.
Martínez-Richa
Antonio
A
Facultad de Química, Universidad de Guanajuato, Noria alta s/n, Gto 36050, Guanajuato, Mexico. richa@quijote.ugto.mx <richa@quijote.ugto.mx>
Joseph-Nathan
Pedro
P
D044946:Biflavonoids; D028241:Camellia sinensis / Q000737:chemistry* / Q000145:classification; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D002392:Catechin; D005419:Flavonoids / Q000737:chemistry; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010636:Phenols / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry* / Q000145:classification; D011108:Polymers / Q000737:chemistry; D013045:Species Specificity; D013662:Tea / Q000737:chemistry* / Q000145:classification; D014334:Tropolone / Q000737:chemistry
D044946:Biflavonoids; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D005419:Flavonoids; D010636:Phenols; D011108:Polymers; D013662:Tea; C056068:theaflavin; D014334:Tropolone; D002392:Catechin