中文摘要：

为比较绿茶、红茶提取物对中波紫外线（UVB）诱导角质形成细胞光损伤的抑制作用，用不同浓度的绿茶、红茶提取物对人表皮角质形成细胞（HaCaT）预处理6h，以60mJ／cm2的剂量照射细胞，比较细胞生存率和细胞上清液中超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-Px）、乳酸脱氢酶（LDH）的活性以及丙二醛（MDA）含量的变化，用荧光法检测细胞内活性氧（ROS）的含量，用流式细胞仪检测细胞的凋亡变化，并对绿茶、红茶的茶多酚及儿茶素类物质含量进行比较。结果表明：与空白对照组相比，uvB辐射模型组的HaCaT细胞活性下降了21．61％，细胞损伤严重；与UVB辐射模型组相比，绿茶、红茶提取物可提高UVB辐射后HaCaT细胞的存活率，提高SOD、GSH-Px活性（尸〈0．01），降低LDH活性、MDA含量和细胞内氧自由基含量（P〈0．01），降低由UVB辐射导致的细胞凋亡率（尸〈0．01），使细胞凋亡率分别降低了6．94％和3．68％；绿茶中茶多酚和儿茶素类物质的含量明显高于红茶，绿茶提取物的抑制效果优于红茶提取物。综合分析以上结果，认为绿茶、红茶提取物可以减少由UVB辐射导致的HaCaT细胞损伤和凋亡，具有光保护作用，其机制与细胞抗氧化能力的增强和氧自由基的加速清除有关，且绿茶提取物的作用效果比红茶提取物的好。

英文摘要：

To compare the photo-protective effect of green and black tea extracts on HaCaT cells damaged from ultraviolet radiation B. Sub-confluent HaCaT cells were incubated for 6 h with different doses of extracts from green tea and black tea, and then irradiated with 60 mJ/cm2 doses of UVB. The change of the cell viability, the activity of superoxide dismutase （SOD）, glutathione peroxidase （GSH-Px）, lactate dehydrogenase （LDH）, and the level of malondialdehyde （MDA） of supernatant were compared. The content of ROS was measured with the fluorescence method. Annexin V/PI double staining was performed to evaluate the change of apoptosis using flow cytometry. In addition, the contents of tea polyphenols and catechins from extracts of green and black tea were also tested. The results were as follows： Compared with control group, the UVB irradiation could seriously harm HaCaT cell and gave rise to 21.61% cell viability decline. Extracts form green and black tea could enhance cell viability, SOD and GSH-Px activity in supernatant under UVB irradiation, and decrease LDH activity, the content of MDA and the content of ROS in cells in dose-dependent manner （P 〈0.01）. Compared with UVB-irradiated model group, the apoptosis rate of HaCaT cell in other groups was decreased by 6.94% and 3.68% respectively. Moreover, the photo-protective effect of green tea extracts was better than that of black tea extracts, which were consistent with the content of tea polyphenols and catechins their contained. Green and black tea extracts could relieve UVB-induced oxidative damage and apoptosis of HaCaT cells, which might be the reason that they raised the oxidase activity and cleared the oxy-radicals in cells. Moreover, the photo-protective effect of green tea extracts against oxidative damage and apoptosis of HaCaT cells from UVB irradiation was better than that of black tea extracts.