大蒜中两种新的甾体皂甙成分及其对血液凝聚性的影响

用大孔树脂（ＡＢ８）柱层析、硅胶柱层析、ＳｅｐｈａｄｅｘＬＨ２０柱层析、及制备性ＨＰＬＣ等方法，从大蒜（ＡｌｉｕｍｓａｔｉｖｕｍＬ．）水溶性部分分到６个化合物，并鉴定其结构，它们分别是ｐｒｏｔｏｉｓｏｅｒｕｂｏｓｉｄｅＢ（Ｉ），ｅｒｕｂｏｓｉｄｅＢ（Ｉ），ｉｓｏｅｒｕｂｏｓｉｄｅＢ（ＩＩ），ｓａｔｉｖｏｓｉｄｅＣ（ＩＶ），腺苷（Ｖ）和色氨酸（ＶＩ）。其中Ｉ和ＩＩ为两个新的甾体皂甙类化合物。并测试了它们对血液系统的作用，发现大蒜总甙有抗血小板聚集和提高纤溶活性，ｉｓｏｅｒｕｂｏｓｉｄｅＢ有明显的延长血液凝固时间和提高纤溶活性，ｐｒｏｔｏｉｓｏｅｒｕｂｏｓｉｄｅＢ有显著的提高纤溶活性，腺苷则有抗血小板聚集活性和提高纤溶活性，ｓａｔｉｖｏｓｉｄｅＣ由于量少未测活性。其余化合物均无活性。

6─或8─脂代─7─氧香豆素与二氢呋喃香豆素的NMR，MS研究

对从重齿毛当归（ＡｎｇｅｌｉｃａｐｕｂｅｓｃｅｎｓＭａｘｉｍｆ．ｂｉｓｅｒｒａｔａＳｈａｎｅｔＹｕａｎ）根及根茎中分得的１２种６－或８－脂代－７－氧－香豆素和８种二氢呋喃香豆素衍生物进行了１Ｈ和１３ＣＮＭＲ分析研究．结合文献．做出规律性总结．运用２ＤＮＭＲ技术．对文献中当归醇类化合物碳谱中的个别错误归属给予了纠正，并首次探讨了此类化合物的ＭＳ裂解途径．

Surface coupling of methyl radicals for efficient low‐temperature oxidative coupling of methane

Selective coupling of methyl radicals to produce C_(2) species(C2H4 and C2H6)is a key challenge for oxidative coupling of methane(OCM).In traditional OCM reaction systems,homogeneous transformation of methyl radicals in O_(2)‐containing gases are uncontrollable,resulting in limited C_(2) selectivity and yield.Herein,we demonstrate that methyl radicals generated by La_(2)O_(3)at low reaction temperature can selectively couple on the surface of 5 wt%Na2WO4/SiO_(2).The controllable surface coupling against overoxidation barely changes the activity of La_(2)O_(3)but boosts the C_(2)selectivity by three times and achieves a C_(2)yield as high as 10.9%at bed temperature of only 570℃.Structure‐property studies suggest that Na_(2)WO_(4) nanoclusters are the active sites for methyl radical coupling.The strong CH_(3)·affinity of these sites can even endow some methane combustion catalysts with OCM activity.The findings of the surface coupling of methyl radicals open a new direction to develop OCM catalyst.The bifunctional OCM catalyst system,which composes of a methane activation center and a CH_(3)·coupling center,may deliver promising OCM performance at reaction temperatures below the ignition temperature of C2H6 and C2H4(~600℃)and is therefore more controllable,safer,and certainly more attractive as an actual process.