Analysis On The Chemical Compounds From Pu-er Tea And Their Antioxidant Activity

Pu-er tea is a Chinese special tea produced by using tea leaves from Yunnan tea variety [Camellia sinensis (Linn.) var. assamica (Masters) Kitamura] and a special post-fermentation processing. It has great potential on domestic and international market. Some researches have shown that there are abundant polyphenol components in Pu-er tea and Pu-er tea possesses a lot of physiological functions. In this study, the chemical compounds of Pu-er tea were isolated and identified by using modern chromatogram and spectrum technology, and their antioxidant activity was evaluated by using DPPH radical scavenging method.Twelve compounds were isolated from Pu-er tea by using chromatogram method and the structures of eleven compounds were deduced from their spectral data as follows: (1) gallic acid,(2) (-)-epicatechin, (3 ) (+) - catechin , (4) gallocatechin, (5) quercetin, (6) kaempferol.(7) myticetin, (8) kaempferol-3-O-Glu-6'-Rha, (9) quercetin-3-O-P-D-glucopyranoside, (10) 2, 5-dihydroxy benzoic acid (11) kaempferol-3-O-β-D-glucopranoside. Among them, (5), (6),(8), (9), (11) were firstly isolated from Pu-er tea.The antioxidant activity of Pu-er tea's fractions successively extracted with chloroform, ethyl acetate, n-butanol and water was evaluated by using DPPH radical scavenging method. The highest antioxidant activity was shown in the ethyl acetate extraction part, followed by n-butanol extraction part, water extraction part and the chloroform extraction part . Among eleven pure compounds isolated from Pu-er tea, Gallic acid (GA) that is abundant in Pu-er tea showed the highest antioxidant activity (SC50=5.30μg/ml), it suggests that GA maybe is one of the most primary biological active component in Pu-er tea. Moreover, the main chemical components in Pu-er tea, such as tea polyphenol, amino acid and catechin etc, were also compared with green tea and black tea.