title: Comparative studies on the physicochemical and antioxidant properties of different tea extracts.
abstract: Tea is one of the most popular drinks next to water. Tea polyphenol is one of the main bioactive constituents of tea with health functions. In order to find the most bioactive tea polyphynols, polyphenol extracts from green tea, black tea and chemical oxidation products of green tea extracts were comparatively studied on the physicochemical and antioxidant properties. Results showed physicochemical and antioxidant properties of polyphenol extracts changed greatly after the chemical oxidation. Hydrogen peroxide induced oxidation products (HOP) possessed the highest antioxidant ability among the four tea polyphenol extracts. Thirteen phenolic compounds and one alkaloid in HOP were identified by reversed phase high-performance liquid chromatography coupled to diode array detection and electrospray ionization mass spectrometry (RP-HPLC-DAD-ESI-MS). Hydrogen peroxide induced oxidation of tea polyphenol extracts could improve the antioxidant activity and could be used to produce antioxidants for food industry.
authors.affiliation: Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin, 300072 People's Republic of China.
authors.forename: Haixia
authors.initials: H
authors.lastname: Chen
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xueming
authors.initials: X
authors.lastname: Lu
authors.forename: Zhishuang
authors.initials: Z
authors.lastname: Qu
keywords: Antioxidant activity; Comparative studies; HPLC-MS; Physicochemical properties; Tea polyphenols