【作者】 杨子娟；

【导师】 郑毅男； 向兰；

【作者基本信息】 吉林农业大学 ， 中药学， 2008， 硕士

【摘要】 马齿苋(Portulaca oleracea L.)广布于全世界温带和热带地区,在许多国家作为药食两用植物使用。马齿苋中含有脂肪酸、萜类、生物碱、香豆素、黄酮、酚酸和挥发油等多种化学成分。现代药理研究表明马齿苋具有抗菌、消炎止痛、松弛肌肉、治外伤和神经保护作用,以及显著的抗氧化和延缓衰老作用。由于目前对马齿苋抗氧化作用的物质基础研究很少,马齿苋的抗氧化活性部位和活性成分还不十分清楚。本研究以马齿苋药材为原料,经70%乙醇回流提取,提取液经AB-8大孔吸附树脂洗脱,洗脱物依次经乙酸乙酯和正丁醇萃取,各萃取相经硅胶柱层析、聚酰胺柱层析、ODS-A反相硅胶柱层析和Sephadex LH-20柱层析等多种柱层析方法进行分离纯化,共获得8个单体化合物,经波谱解析(一维核磁共振氢谱和碳谱以及氢-氢化学位移相关谱、异核多量子相关谱和多键碳氢相关谱等二维核磁共振谱)鉴定了其中7个化合物,分别为咖啡酸(1)、马齿苋酰胺E(2)、马齿苋酰胺A(3)、马齿苋酰胺B(4)、橙皮苷(5)、腺苷(6)和腺嘌呤(7)。其中,化合物1、5、和7为首次从马齿苋中分离得到。此外,本研究利用DPPH自由基清除法以及双氧水诱导的大鼠脑匀浆脂质过氧化模型,首次对马齿苋的各个部位,以及分离得到的新型酚性生物碱进行了较为系统的抗氧化活性研究。两种抗氧化分析方法均表明:马齿苋水提取物中乙酸乙酯相和正丁醇相的抗氧化活性最强,且呈剂量依赖性,是马齿苋的主要抗氧化活性部位;总水提物的活性较弱;而剩余水相在DPPH实验中表现出最弱的抗氧化活性,在脂质过氧化实验中,当为中等浓度(92.81μg/mL和185.63μg/mL)时,有明显的增强脂质过氧化作用。单体化合物中,咖啡酸活性最强。马齿苋酰胺A、马齿苋酰胺B和马齿苋酰胺E显示出一定的抗氧化活性。酚性生物碱清除DPPH自由基的活性顺序为马齿苋酰胺B>马齿苋酰胺A>马齿苋酰胺E,均强于阳性对照抗坏血酸和生育酚;其抑制双氧水诱导的大鼠脑匀浆脂质过氧化实验中,马齿苋酰胺E的活性最强,且呈剂量依赖性,其半数抑制浓度为73.13μM,与咖啡酸(72.09μM)接近,马齿苋酰胺A和马齿苋酰胺B低浓度时没有明显的抑制脂质过氧化活性,只在高浓度(大于200μM)时对脂质过氧化具有抑制作用。本课题的创新之处为:首次利用双氧水诱导的大鼠脑匀浆脂质过氧化法,对马齿苋不同部位和分离得到的新型酚性生物碱进行抗氧化活性研究,进一步阐明了马齿苋抗氧化作用的物质基础和作用机制,为新的天然抗氧化剂的开发提供了理论依据,对将来马齿苋用于开发为保健食品或者一些慢性疾病的辅助治疗具有重要的现实意义。更多还原

【Abstract】 Portulaca oleracea（Portulacaceae family） is a well-known edible plant,which is widespread in temperate and tropical regions of the world.Many types of chemical compounds were present in this plant,including unsaturated fatty acids,terpenoids,alkaloids,coumarins,flavonoids,phenolic acids and volatile oil.It is also used as folk medicine in many countries with various pharmacological effects such as antibacterial,analgesic, antiinflammatory,muscle relaxation,anthelminthic,wound healing and neuroprotective activities.It is noteworthy that many researches have shown that P.oleracea has strong antioxidant activity.However,the antioxidant ingredients in P.oleracea is not fully understood yet.In this study,the crude drug of P.oleracea was extracted with 70%ethanol.The condensed extract was subjected on AB-8 resin,and the eluates were partitioned with ethyl acetate and n-butanol,sequentially.Eight compounds were isolated from above extracts using various chromatographic methods,such as silica gel column chromatography,polyamide column chromatography,ODS-A column chromatography and polydextran gel SephadexLH-20 column chromatography.Based on various spectroscopic data(¹H-NMR, ¹³C-NMR,H-H COSY,HMQC and HMBC),seven compounds were identified as caffeic acid（1）,oleracein E （2）,oleracein A（3）,oleracein B（4）,hesperidin（5）,adenosine（6） and adenine（7）.Compound 1,5,and 7 were isolated from P.oleracea L.for the first time.Antioxidant activities of different fractions and phenolic compounds from Portulaca oleracea were determined,based on scavenging activity against DPPH radical and inhibitory effect on hydrogen peroxide-induced lipid peroxidation in rat brain homogenates.In both assays,n-butanol fraction and ethyl acetate fraction were shown to be the more potent antioxidants,and were in a dose-dependent manner, followed by the whole water fraction.The remaining water fraction showed the weakest DPPH free-radical scavenging activity and stimulated lipid peroxidation significantly at the median concentration（92.81μg/mL and 185.63μg/mL）.As for individual compound,caffeic acid showed the strongest antioxidant activity. Phenolic alkaloids also served as a new class of antioxidant agent in this plant.The DPPH radical-scavenging activities of three phenolic alkaloids,i.e.oleracein A（OA）,oleracein B（OB） and oleracein E（OE）,were higher than the positive control,ascorbic acid and a-tocopherol,being in the following order:OB>OA>OE. Among three alkaloids,OE was most potent in preventing hydrogen peroxide-induced formation of MDA in a dose-dependent manner,with IC₅₀ value of 73.13μM,close to that of caffeic acid（72.09μM）.However,OA and OB showed no activity at low concentration and significant inhibitory activity occurred only at high concentrations above 200μM.The innovative point of this study was that we first determined the antioxidant activities of different fractions and phenolic compounds from Portulaca oleracea depending on the inhibitory effect on hydrogen peroxide-induced lipid peroxidation in rat brain homogenates.This study further elucidated the antioxidant ingredients of P.oleracea and their action mechanism.It would be very important for the future usage of P. oleracea as functional food or potential drugs for the prevention and treatment of some chronic diseases.更多还原