【作者】 段小娟；

【导师】 王斌贵；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋化学， 2007， 硕士

【摘要】 本论文采用DPPH（α,α-二苯基-β-苦味酰自由基）自由基清除法和β-胡萝卜素-亚油酸氧化法对采自青岛沿海的28种海藻的粗提物进行了抗氧化活性筛选,以2,6-二叔丁基-4-甲基苯酚（BHT）、没食子酸（GA）和抗坏血酸（AscA）作为阳性对照。结果发现大多数海藻都表现了不同程度的抗氧化活性。其中,鸭毛藻Symphyocladia latiuscula的抗氧化活性最强。鸭毛藻粗提物的乙酸乙酯相在两种方法中都表现了最强的抗氧化活性,乙酸乙酯相通过VLC被进一步分为7个组分（F1–F7）。其中F1对DPPH自由基的清除率最强,而在β-胡萝卜素-亚油酸实验中F4的抗氧化活性最强。另外,还测定了粗提物、各相和各组分的总酚含量和还原能力。其中28种海藻粗提物的总酚含量变化范围为0.10到8.00 mg没食子酸/g海藻干重,还原能力变化范围为0.07到11.60mg抗坏血酸/g海藻干重。统计分析发现,对于粗提物和各相,抗氧化活性和总酚含量以及和还原能力都存在很强的正相关。这些结果将有助于进一步分析抗氧化活性强的海藻,从而确定活性原理。由于鸭毛藻的抗氧化活性最强,所以对它的化学成分做进一步的调查。采用硅胶柱层析、制备薄层层析、凝胶Sephadex LH-20柱层析、反相硅胶柱层析、半制备HPLC及重结晶等手段分离得到19个化合物。运用各种现代波谱技术（IR、UV、ESI-MS、EI-MS、FAB-MS、HR-FAB-MS、1D-NMR、2D-NMR等）鉴定了它们的结构,其中包括4个新化合物:化合物S1 1-（2,3,6-三溴-4,5-二羟基苄基）-四氢吡咯-2-酮、化合物S2 1,2-双（2,3,6-三溴-4,5-二羟基苯基）乙烷、化合物S3 6-（2,3,6-三溴-4,5-二羟基苄基）-2,5-二溴-3,4-二羟基苄甲醚和化合物S4 2,3,6-三溴-4,5-二羟基苄甲砜,以及5个已知化合物和10个首次从鸭毛藻中报道的化合物。分离到的溴酚化合物S1-S10具有显著的DPPH自由基清除活性,其IC₅₀值在8.1-24.7μM之间,且它们的活性是BHT(IC₅₀ = 81.8μM)的3.3到10倍左右。初步的构-效关系研究发现,分子中的羟基数目与活性有直接关系。更多还原

【Abstract】 The extracts obtained from 28 species of marine algae collected along the coastline of Qingdao were evaluated for their antioxidant activity （AA） versus the positive controls butylated hydroxytoluene （BHT）, gallic acid （GA）, and ascorbic acid （AscA） by using two methods both scavenging DPPH （α,α-diphenyl-β-picrylhydrazyl） radical assay andβ-carotene-linoleate assay. Most of the tested samples displayed antioxidant activity in various degrees. Among them, the extract of Symphyocladia latiuscula exhibited the strongest AA.In addition, the ethyl acetate-soluble fraction isolated from the crude extract of S. latiuscula exhibited the highest antioxidant activity in both assay systems. This fraction was further fractionated into seven subfractions （F1–F7） by vacuum liquid chromatography （VLC）. F1 and F4 were found to be the most effective subfractions in scavenging DPPH radical assay and inβ-carotene-linoleate assay, respectively.The total phenolic content （TPC） and reducing power （RP） in all of the extracts, fractions, and subfractions F1-F7 were also determined. The TPC of the 28 extracts ranged from 0.10 to 8.00 of gallic acid equivalents （mg/g seaweed dry weight） while the RP ranged from 0.07 to 11.60 of ascorbic acid equivalents （mg/g seaweed dry weight）. Highly positive relationships between AA and TPC as well as between AA and RP were found for the extracts and fractions. The results obtained from this study will be helpful to further analyze those marine algal species that contain the most antioxidant activity in order to identify the active principals.The extract of the S. latiuscula had the strongest antioxidant activity. Therefore this species was selected for further chemical investigation. 19 compounds were isolated by the combination of column chromatography on silica gel, preparative thin layer chromatography （PTLC）, and Sephadex LH-20, RP-18, semi-preparative HPLC, and recrystallization, and were elucidated by means of spectroscopic methods including IR, UV, ESI-MS, EI-MS, FAB-MS, HR-FAB-MS, 1D-NMR and 2D-NMR, including four new compounds, namely, 1-（2,3,6-tribromo-4,5-dihydroxybenzyl）-pyrrolidin-2-one （S1）, 1,2-bis（2,3,6-tribromo-4,5-dihydroxyphenyl）ethane （S2）, 6-（2,3,6-tribromo-4,5-dihydroxybenzyl）-2,5-dibromo-3,4-dihydroxybenzyl methyl ether （S3）, and 2,3,6-tribromo-4,5-dihydroxybenzyl methyl sulfone （S4）, Five known compounds and ten compounds isolated from S. latiuscula for the first time.The isolated bromophenol compounds S1-S10 showed strong activities, with IC₅₀ values ranging from 8.1 to 24.7μM. These radical scavenging activities were 10- and 3.3-fold more potent than that of butylated hydroxytoluene (IC₅₀ = 81.8μM). Structurally, This result is in good agreement with the former observation that free radical scavenging activity increased significantly with the numbers of hydroxyl groups in related molecules.更多还原