中文摘要：

为了研究中草药米口袋的清除自由基活性及其成分，用2：1的甲醇：氯仿超声提取米口袋成分，并用石油醚、乙酸乙酯和正丁醇依次进行萃取，利用DPPH法、邻二氮菲-Fe^2＋氧化法和AP-TEMED法进行清除自由基活性实验，同时与合成抗氧化剂BHT进行对照。结果显示乙酸乙酯提取物（EAF）具有最高的清除自由基活性，大于人工合成抗氧化剂BHT。利用硅胶，RP-18和Sephadex LH-20对其进行活性追踪分离，得到3种纯的清除自由基活性成分。利用1D、2DNMR和ESI-MS对其结构进行鉴定。结果显示为槲皮素-3-O-葡萄糖甙，芹菜素和4′，7-二羟基黄酮。抗氧化活性大小顺序为槲皮素-3-O-葡萄糖甙〉芹菜素〉4′，7-二羟基黄酮〉EAF〉BHT。含酚羟基化合物的清除自由基活性与其结构密切相关。活性大小主要取决于酚羟基的数目。本研究结果证明：米口袋及其活性成分具有很强的清除自由基作用。可作为一种高效的新型清除自由基天然食品添加剂使用，具有广泛的应用前景。

英文摘要：

In order to study free radical scavenging activities and principals, Gueldenstaedtia multiflora Bge. （GMB） was extracted with methanol：chloroform（2 ： 1） in an ultrasonator, and the extraction was then partitioned with petroleum ether, EtOAc and BuOH successively. Free radical scavenging activity （FRSA） of the extractions was evaluated by using DPPH radical scavenging assay, the 1,10-phenanthroline-Fe^2＋ oxidative and the AP-TEMED assays, and compared with that of BHT. The EAF （ethyl acetate-soluble fraction） exhibited the highest FRSA, which was greater than that of BHT. Furthermore, bioactivity-guided chromatographic fractionation was conducted by repeated column chromatography over a silica gel, RP- 18, and Sephadex LH - 20 to obtain three pure antiradical compounds. Their structures were determined by interpretation of the 1D and 2D NMR, as well as mass spectral data. The result demonstrated that quercetin 3 - O- β - D- glucopyranoside, apigenin and 4′, 7-dihydroxyflavone were the major antiradical constituents in GMB. The FRSA of the compounds decreased in the following order： quercetin 3 - O-β- D- glucopyranosid〉apigenin〉4′, 7-dihydroxyflavone〉EAF〉BHT. The FRSA of phenolic compounds is correlated to their chemical structures. In general, the FRSA of phenolics depends mainly on the number of hydrogen-donating hydroxyl groups on the aromatic ring of the phenolic molecules. Our results indicate that the extract from GMB as well as isolated antiradical constituents is promising antioxidants which can be used as food additives.