【作者】 王华；

【导师】 宛晓春； 李大祥；

【作者基本信息】 安徽农业大学 ， 茶学， 2007， 硕士

【摘要】 茶红素是一类复杂的红褐色的不均一性酚性化合物的混合物,相对分子量在700—40000之间,主体成分为儿茶素类的聚合体。茶红素具有异质性,其单体很难分离纯化,它的结构、组成及性质也都不甚清晰。目前,有关茶红素的制备报道也较少,主要是有机溶剂提取法和色谱分离法。近六十年来,茶红素化学的研究一直是国际上茶叶界关注的焦点之一,但茶红素的开发利用至今为止未能取得突破性的进展。本文首先采用超声浸提、有机溶剂分级萃取、乙醚沉淀从祁门红茶中分级制备了五种不同极性的茶红素部分PBP-1～PBP-5。经HPLC检测,五个部分均无儿茶素、咖啡碱、茶黄素的残留,纯度较高。其次对五种不同极性的茶红素部分的还原力以及清除自由基能力进行测定,结果表明PBP-1～PBP-5均有还原力。在13.2～150μg/ml范围内,随着浓度的升高,PBP-1～PBP-5的还原力逐渐上升。随着茶红素极性的增加,其还原力逐渐降低;在Fenton体系中,PBP-1～PBP-5在13.2～100μg/ml范围内,随着浓度的升高,其清除·OH能力逐渐上升,并且随着茶红素极性的增加,其清除能力逐渐减弱;在邻苯三酚自氧化体系中,PBP-1～PBP-5在13.2～100μg/ml范围内,对O₂^-的最高抑制率为48.22%,抑制率主要分布在10～25%之间;在DPPH体系中PBP-1～PBP-5在13.2～100μg/ml范围内,随着浓度的升高,其清除DPPH自由基能力逐渐增强,并且随着茶红素极性的增加,其清除能力逐渐减弱。所有这些结果表明,茶红素与其主要前体物质儿茶素和茶黄素相似,仍具有一定的自由基清除能力,这可能与其结构中仍然保留了一些活性酚羟基和苯骈卓酚酮结构有关。本研究结果为茶红素——这类红茶中含量最丰富的多酚类物质的生物学活性研究以及其开发利用提供了前期理论基础。更多还原

【Abstract】 Thearubigins are heterogeneous acidic phenolic pigments in black tea,which are mainly flavanol polymers with a molecular weight distribution of 700-40000 and contribute to the color and taste of black tea.Because of their heterogeneity, thearubigins are difficult to be purified from black tea,which lead to the limited information on their structure,composition and characteristics.By far,there are a few reports on their preparation,which only focused on the solvent extraction and chromatographic separation.In the past sixty years,thearubigins have intrigued many research groups to explore,but there still have no breakthrough on their characteristic.In this paper,five thearubigin fractions named after PBP-1 to PBP-5 were prepared from Keemun black tea with solvent extraction and ethyl ether precipitation. All of them were free of catechins,theaflavins and caffeine by the analysis of HPLC. In the reducing power tests,the five thearubigin fractions at the concentration of 13.2-150μg/ml had been shown to have a reducing power in a dose-dependent manner.With the polarity increase of thearubigin fractions,the reducing power was tend to decrease.In the Fenton system,the scavenging activities of five thearubigin fractions to hydroxyl radicals were raised with the increase of their concentration from 13.2μg/ml to 150μg/ml.With the polarity increase of thearubigin fractions, their scavenging capacity was decreased.In the pyrogallol autooxidation system, five fractions at the concentration of 13.2-150μg/ml had a slight inhibition of the formation of superoxide anion with the maximal inhibition as 48.22%.The inhibition percentage was mainly ranged from 10%to 25%.In the DPPH system,all of fractions at 13.2-100μg/ml executed scavenging activities in a dose-response way as similar as the performance in the Fenton system.Moreover,their scavenging activities to DPPH radicals were decreased with the increase of the polarity.Those results have shown that thearubigins as like as their major precursors-catechins and theaflavins are capable to eliminate free radicals,which mainly due to the contribution of the residue of the active phenolic hydroxyl groups and benzotropolone groups at the thearubigin molecule.Thearubigins-the most abundant polyphenolic substances in black tea may have a potential to execute biological effects after tea drinking.更多还原