title: Thermal effects on the stability and antioxidant activity of an acid polysaccharide conjugate derived from green tea.
abstract: A technique of high-performance gel permeation chromatography (HPGPC)-evaporative light-scattering detection and circular dichroism (CD) was developed for the measurement of thermal effects on the homogeneity and conformation of polymeric carbohydrate conjugates and was applied to an acid polysaccharide conjugate (GTa) isolated from the composite enzyme extract of green tea. Incubations in water at 40 and 70 degrees C for 1.0, 2.5, and 5.0 h have no effects on GTa. In contrast, when incubated in water for 1.0, 2.5, and 5.0 h at 98 degrees C, a single symmetrical peak corresponding to GTa in HPGPC was split into two adjacent peaks representing two different components formed, and CD spectra revealed an additional positive Cotton effect at 216 nm. To contribute toward our understanding of thermal effects of this polymeric carbohydrate conjugate on antioxidant activity, GTa and related heat-treated samples (GTa-HTI, GTa-HTII, and GTa-HTIII), the latter being obtained from 1.0, 2.5, and 5.0 h incubations at 98 degrees C, respectively, were subjected to the self-oxidation of 1,2,3-phentriol assay and found to have respective scavenging activities in a concentration-dependent manner. In comparison with GTa, the scavenging potency of heat-treated samples was similar at the dosage range of 50-300 microg/mL but became stronger with continually increasing concentration. Moreover, the present study also provides further insights into the optimal preparation of tea polysaccharide conjugates.
authors: Key Laboratory of Machining and Quality Control of Tea and Beverage Plants, National Tea Industry Engineering Research Center, Tea Research Institute of China Academy of Agricultural Sciences, Hangzhou 310008, China. biomed528@163.com
authors: Xiaoqiang
authors: X
authors: Chen
authors: Yang
authors: Y
authors: Ye
authors: Hao
authors: H
authors: Cheng
authors: Yongwen
authors: Y
authors: Jiang
authors: Yalin
authors: Y
authors: Wu
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D002942:Circular Dichroism; D004355:Drug Stability; D016166:Free Radical Scavengers / Q000494:pharmacology; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D011134:Polysaccharides / Q000737:chemistry* / Q000494:pharmacology*; D013662:Tea / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D011134:Polysaccharides; D013662:Tea