Characterization of the chemical differences between solvent extracts from Pu-erh tea and Dian Hong black tea by CP-Py-GC/MS

Solvent extracts from a type of Pu-erh tea and Dian Hong black tea were characterized by Curie-point pyrolysis-gas chromatography-mass spectroscopy (CP-Py-GC/MS). The ethyl-acetate extracts from both teas showed similar CP-Py-GC/MS results, with main pyrolytic products of carbon dioxide, caffeine, o-phenols, and phthalate esters. During pyrolysis, the n-butanol extract from Pu-erh tea formed carbon dioxide (38.92% of total pyrolytic products), alkaloids (49.7%), and nitrogen oxides (8.38%), as well as a small fraction of esters. The n-butanol extract from Dian Hong tea formed mainly alcohols, amines, esters, phenols, carboxylic acids, and alkaloids. The raw theabrownin extracts (ethanol precipitates) from the two teas produced substantially different CP-Py-GC/MS results. The raw theabrownin extract from Puerh tea formed mostly carbon dioxide during pyrolysis, whereas the counterpart extract from Dian Hong tea formed mainly carbon dioxide (48.23%) and nitrogen oxides (35.39%). The 3.5-100 kDa fractions separated from the theabrownin extracts of the two teas showed similar CP-Py-GC/MS results, whereas the fractions <3.5 kDa and >100 kDa formed substantially different pyrolytic products. These results showed that solvent extracts from Pu-erh tea and Dian Hong tea had substantially different chemical compositions and structures. The study suggested that CP-Py-GC/MS can be used to effectively identify chemical differences between tea extracts. (C) 2012 Elsevier B.V. All rights reserved.