顶空萃取-气相色谱-质谱法分析芝麻油中的挥发性成分

建立了采用顶空萃取 -气相色谱 -质谱联用技术分离鉴定芝麻油中的气味成分的方法。结果表明 :经NIST质谱数据库检索和文献对照 ,共检出并确定 47种成分 ,可归纳为 6组物质 ,分别为含氧的醇、醛、酯类、吡嗪类、噻唑类、噻吩类、呋喃类、硫醇及硫醚类、烃类。其中以吡嗪类、噻唑类、呋喃类为芝麻油中气味成分的主要物质。     

直接注射-多级质谱全扫描法快速分析枸杞子化学成分组

由于色谱分离需要耗费大量的时间,导致传统LC-MS研究中药成分的分析通量较低,而多级质谱全扫描（MS/MSALL）采用了气态分段技术（GPF）,可以在直接注射（DI）模式下,采集每个表观质量数MS1信号的MS2图谱,实现MS1-MS2数据列表的高通量构建。为快速表征枸杞子化学成分组,本研究采用DI-MS/MSALL全面采集枸杞子提取物中各化学成分的多级质谱数据,根据高分辨MS1和MS2碎片离子信息推导质谱裂解途径,结合数据库检索以及相关文献,从枸杞子中初步鉴定了38个化学成分,包括1个氨基酸类、19个有机酸类、2个糖脂类、6个苯丙素类、1个黄酮类、6个生物碱类以及3个酰胺类化合物。DI-MS/MSALL可作为中药等复杂体系快速全面定性分析的有力工具。     

青胶蒲公英化学成分鉴定及质谱裂解规律研究

采用超高效液相色谱-四极杆/静电场轨道阱高分辨质谱（UHPLC-Q/Orbitrap HRMS）对青胶蒲公英中的化学成分进行快速分析鉴定。将青胶蒲公英的根、叶干燥粉碎,经超声/微波辅助萃取,采用Waters ACQUITY BEH C18色谱柱 (100 mm×2.1 mm×1.7 μm),以0.1%甲酸水溶液和乙腈为流动相进行梯度洗脱。洗脱液经大气压化学电离源（APCI）离子化后,采用全扫描-数据依赖型二级质谱扫描模式进行数据采集。将预处理后的数据与中药数据库及在线数据库等比对分析,包括一级精确质荷比、同位素峰分布以及二级质谱图匹配,共鉴定出164种化合物,包括黄酮类、香豆素类、萜类、有机酸类、生物碱类、木质素类等,同时对部分鉴定成分的质谱裂解规律进行推导,有助于黄酮类等化合物的结构解析,为青胶蒲公英中黄酮类等成分结构类似物的快速鉴定提供了重要的实验依据。     

UPLC-LTQ-Orbitrap-MS法快速分析鬼箭羽中的化学成分

利用UPLC-LTQ-Orbitrap-MS技术结合文献报道的鬼箭羽已知化学成分及其裂解规律快速鉴定鬼箭羽药材中的化学成分。利用文献中鬼箭羽化学成分的分子式、相对分子质量、碎片离子等信息建立鬼箭羽快速识别数据库,依据化合物的精确分子质量、色谱保留时间、特征碎片离子等信息对已知成分进行验证;对于鬼箭羽中未知成分,通过总结同类化合物的质谱裂解规律,并查阅相关文献确定其相对分子质量、特征碎片离子、色谱保留时间等信息,并进行结构表征。实验共鉴定得到65种成分,包括36种黄酮类、4种酚酸类、7种三萜类、12种脂肪族和6种其他类成分,其中,有28种化合物是首次在鬼箭羽中发现。该方法可以快速、全面地分析鬼箭羽药材中的化学成分,可为鬼箭羽药材的质量控制研究奠定基础。     

高效液相色谱-高分辨质谱法鉴定拉萨大黄化学成分

建立了高效液相色谱-高分辨质谱法分析鉴定拉萨大黄化学成分。选用Agilent Zorbax SB-C18柱（150 mm×4.6 mm×5 μm）,以乙腈和水为流动相进行梯度洗脱,流速0.5 mL/min;采用电喷雾离子源,在正、负离子模式下对拉萨大黄提取物进行一级和多级全扫描质谱分析。综合分析化合物的色谱和质谱行为,并结合对照品、文献和数据库等相关数据鉴定化合物。在负离子模式下,鉴定出63种化合物;正离子模式下,鉴定出54种化合物。所检测到的化合物包括22种鞣质类、28种茋类、6种黄酮类、3种苯丙酸类、2种苯丁酮类和2种有机酸类,其中有53种化合物为在该药材中首次发现,且未发现蒽醌类成分。该方法快速、灵敏,不仅提高了拉萨大黄复杂基质中微量化合物的鉴定效率,同时实现了对拉萨大黄提取物中不同类型化合物的分析鉴别,为进一步阐明拉萨大黄的药效物质基础及质控标准提供了科学依据。     

基于UPLC-Q-Exactive Orbitrap-MS分析藏药诃子与毛诃子化学成分

采用超高效液相色谱-四极杆-静电场轨道阱高分辨质谱联用技术(UPLC-Q-Exactive Orbitrap-MS),在电喷雾负离子模式下对使君子科(Combretaceae)榄仁树属(Terminalia Linn.)成分相近的藏药诃子与毛诃子的化学成分进行快速识别和鉴定。采用Acquity UPLC HSS T3色谱柱(2.1 m×100 mm×1.8μm),以含0.1%乙酸的甲醇-0.1%乙酸水溶液为流动相进行梯度洗脱。通过高分辨质谱给出的分子离子峰和碎片离子数据,结合相关文献和对照品,从诃子中鉴定出94个成分,包括28个特有成分,从毛诃子中鉴定出96个成分,包括30个特有成分,二者共有成分66个,其中12个鞣质类成分为首次从榄仁树属内发现。本研究可为诃子与毛诃子的快速鉴定,质量控制及阐明其药效基础提供参考。     

红花中色素类化合物的电喷雾多级串联质谱研究

利用电喷雾多级串联质谱技术研究了红花提取物中4种色素类成分,即红花红色素、羟基红花黄色素A、红花黄色素A和红花黄色素B。通过多级串联质谱技术,获得4种化合物的分子离子峰,并由此获得分子质量信息;根据一些特征中性碎片的丢失,提出了红花中4种色素类成分的质谱碎裂规律。根据得到的分子质量和碎片信息,并与文献中的已知化合物比较,建立了红花中色素类化合物的快速分析、质谱鉴定的方法。     

基于UHPLC-LTQ-Orbitrap的发酵玫瑰茄化学成分筛查和研究

本研究采用高效液相色谱-线性离子阱-静电场轨道质谱（UHPLC-LTQ-Orbitrap MS）技术,在电喷雾负离子模式下,对玫瑰茄水提液及其发酵液中有机酸类、黄酮类、花青素类和木质素类化学成分进行分析鉴定。选取Agilent Zorbax SB C18色谱柱（250 mm×4.6 mm×5 μm）,以0.1%甲酸水溶液（A）-甲醇（B）为流动相,流速1 mL/min,梯度洗脱分析。根据高分辨质谱提供的精确相对分子质量数据和多级质谱碎片离子,获取目标化合物的相对分子质量和结构信息。结合保留时间、对照品及相关参考文献等信息,共筛选鉴定出41种化合物,包括34种有机酸类、4种黄酮类、2种花青素类以及1种木脂素类。结果表明,玫瑰茄发酵前后,其活性成分的种类及含量均呈现不同程度的变化,该方法阐明了玫瑰茄发酵前后化学成分的变化,可为玫瑰茄的进一步研究提供参考。     

高效液相色谱-四极杆-静电场轨道阱高分辨质谱分析桑葚中黄酮类和多酚类物质

为了更好地利用桑葚这一药食同源果品,采用高效液相色谱-四极杆-静电场轨道阱高分辨质谱对桑葚提取物中黄酮类和多酚类成分进行分析研究。采用Syncronis C18 色谱柱（100 mm×2.1 mm,1.7 μm）,以乙腈-0.1%甲酸水溶液为流动相,流速0.2 mL/min,梯度洗脱分析。根据高分辨质谱提供的准分子离子峰和碎片离子信息,分析得到化合物的相对分子质量和结构信息。结合化合物的保留时间、对照品和相关文献数据,共鉴定出5种黄酮类成分和3种多酚类成分,分别为芦丁、异槲皮素、山奈酚-7-葡萄糖苷、二氢槲皮素、槲皮素、原儿茶酸、绿原酸和咖啡酸。通过讨论化合物的质谱碎裂规律,为化合物的结构鉴定提供依据。该方法可快速分析桑葚中黄酮类和多酚类成分,为合理开发桑葚的药用、食用价值奠定化学基础。     

基于UHPLC-Q-TOF-MS/MS联合分子网络策略快速分析紫菀中肽类成分

本文建立了超高效液相色谱-四极杆-飞行时间串联质谱(UHPLC-Q-TOF-MS/MS)法联合分子网络策略快速分析紫菀中肽类成分。采用ACQUITY UPLC^? HSS T3柱(100 mm×2.1 mm×1.8μm),以乙腈-水为流动相进行梯度洗脱,在正离子模式下,收集紫菀75%乙醇提取物的MS/MS数据,并创建GNPS分子网络。根据标准品、精确相对分子质量、碎片离子等信息,共鉴定出紫菀中43个肽类成分,包括31个环肽类和12个直链肽类,其中分别有16个和8个成分可能为潜在的新型环肽类和直链肽类化合物。UHPLC-Q-TOF-MS/MS联合分子网络策略能够快速、准确、全面地鉴定紫菀中的肽类成分,可为进一步分离紫菀化学成分和研究药效物质基础提供依据。     

二维液相色谱-质谱法研究犬肾小管上皮细胞脂质组成及马兜铃酸(Ⅰ)对其影响

采用在线正反相二维液相色谱-质谱联用技术研究了犬肾小管上皮细胞脂质组成及马兜铃酸(Ⅰ)对其影响。二维色谱的第一维用于分离不同种类脂质,第二维用于分离同类脂质的不同分子,进而利用高分辨质谱对脂质分子进行检测。该方法减少了共流出,降低了电离抑制,提高了灵敏度与准确性。借助精确质荷比检索数据库、高分辨二级质谱和当量碳数与保留时间规律等方法检测了犬肾小管上皮细胞中13类脂质的1 416个脂质分子。选取11种外源性脂质标准品进行方法验证,方法的线性关系、检测限、重复性均满足检测要求。在此基础上,考察了犬肾小管上皮细胞暴露于马兜铃酸(Ⅰ)后的脂质变化情况,对改变含量2～4倍的15个脂质分子进行了鉴定。该实验结果可为马兜铃酸的毒理、病理研究和相关疾病的临床诊断提供丰富的信息,并展现了二维液相色谱 质谱法在脂质组学研究中广阔的应用前景。     

Visualization and electron diffraction on cryosections of stratum corneum: a utopia?

The skin acts as an effective barrier to protect the body against penetration of substances from the environment and against desiccation. The main barrier function resides in the stratum corneum, and more specifically in the intercellular lipid domains. Several techniques have been used to elucidate the local lipid crystal arrangements in these domains, but they either needed an extensive pretreatment of the skin with the risk of damaging the native structure, or were not suited to obtain local structure information as bulk quantities of stratum corneum were required. In this paper a method of performing local structure analysis (electron diffraction) on cryo-fixed specimens is described. Therefore a cold chain procedure was used to obtain cryosections of stratum corneum. On these sections visualization and electron diffraction at low temperature were carried out.
Using a so-called tape sandwich method, cryosections were prepared in which corneocytes and lipid matrix could easily be distinguished. Moreover, detailed cellular components such as desmosomes and intracellular lipid domains were observed. However, probably due to the limited amount of intercellular lipids in the stratum corneum, electron diffraction on cryosections did not result in diffraction patterns that were undoubtedly originating from the intercellular lipids. In the electron diffraction patterns of a skin lipid model system reflections were present that were indicative of hexagonal and orthorhombic sublattices. The d-spacings of these reflections were similar to the spacings of the high-intensity reflections of the X-ray diffraction pattern of the same mixture. This showed agreement between a bulk and a local technique, X-ray and electron diffraction.     

Mass spectrometric analysis of long-chain lipids

Electrospray and matrix assisted laser desorption ionization generate abundant molecular ion species from all known lipids that have long chain fatty acyl groups esterified or amidated to many different polar headgroup features. Molecular ion species include both positive ions from proton addition [M+H](+) and negative ions from proton abstraction [M-H](-) as well as positive ions from alkali metal attachment and negative ions from acetate or chloride attachment. Collisional activation of both MALDI and ESI behave very similarly in that generated molecular species yield product ions that reveal many structural features of the fatty acyl lipids that can be detected in tandem mass spectrometric experiments. For many lipid species, collision induced dissociation of the positive [M+H](+) reveals information about the polar headgroup, while collision induced dissociation of the negative [M-H](-) provides information about the fatty acyl chain. The mechanisms of formation of many of these lipid product ions have been studied in detail and many established pathways are reviewed here. Specific examples of mass spectrometric behavior of several molecular species are presented, including fatty acids, triacylglycerol, phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol, ceramide, and sphingomeylin.     

Cryo-electron diffraction as a tool to study local variations in the lipid organization of human stratum corneum

The human skin provides the body with a barrier against transepidermal water loss and the penetration of harmful agents (e.g. microbes) from outside. This barrier function is produced mainly by the outermost, nonviable layer of the epidermis, the stratum corneum (SC). The SC consists of terminally differentiated corneocytes surrounded by a continuous intercellular lipid domain, which contains mostly ceramides, cholesterol and free fatty acids. Small- and wide-angle X-ray diffraction studies have elucidated the lamellar and lateral lipid organizations in these domains. However, these techniques require bulk quantities of SC, as a result of which local structure information on the lipids cannot be obtained. Insights to these local lipid arrangements are important when new transdermal drug delivery systems have to be developed. Therefore, the technique of electron diffraction arose as a tool to study the lateral packing of the lipids in the intercellular domains of SC, locally. In a previous study, the suitability of electron diffraction was demonstrated using a lipid model system that resembled the lipid composition of the SC. The spacings calculated from the electron diffraction patterns were in good agreement with the spacings revealed by wide-angle X-ray diffraction. The results presented here succeed this previous study. We improved the microscope settings and developed a new preparation method to study ex vivo human SC by cryo-electron diffraction. The method is based on the conventional tape-stripping method and offers the possibility to study depth-related changes in the lipid organization of human SC. Diffraction patterns of both hexagonal and orthorhombic lipid lattices have been recorded with spacings that resembled those found in human SC by wide-angle X-ray diffraction. After lipid extraction, such diffraction patterns could no longer be detected in the samples.     

Forkhead box protein O1 (FoxO1) regulates lipids metabolism and cell proliferation mediated by insulin and PI3K-Akt-mTOR pathway in goose primary hepatocytes

In order to explore the role of forkhead box protein O1 (FoxO1) in the lipid metabolism and cell proliferation, goose primary hepatocytes were isolated and incubated with insulin or PI3K-Akt-mTOR pathway dual inhibitor NVP-BEZ235, and then transfected with FoxO1 interference plasmid. The related parameters of lipid metabolism and cell proliferation were measured. The results firstly showed that FoxO1 interference increased the intracellular TG and lipids concentration (P < 0.05); and increased the proliferative index (PI), cell DNA synthesis, protein expression of Cyclin D1 in goose primary hepatocytes (P < 0.05). Secondly, the co-treatment of insulin and FoxO1 interference increased the mRNA level and protein content of Cyclin D1 (P < 0.05); however, there was no significant difference between the insulin treatment and the co-treatment of insulin and miR-FoxO1 interference in the intracellular TG and lipids concentration and PI (P > 0.05). Lastly, the decrease of intracellular TG and lipids concentration and PI induced by NVP-BEZ235 was up-regulated by FoxO1 interference significantly (P < 0.05). In summary, FoxO1 could regulate the lipids metabolism and cell proliferation mediated by PI3K-Akt-mTOR signaling pathway in goose primary hepatocytes. Further investigations are required to highlight the potential role of FoxO1 in the lipid metabolism and cell proliferation mediated by insulin in goose primary hepatocyte.     

Lipid losses during processing of cardiac muscle for electron microscopy

The lipid retaining properties of several methods of processing tissue for electron microscopy (EM) have been assessed quantitatively. Guinea-pig hearts were perfused in vitro at 37°C with ³H-oleic acid bound to albumin. The hearts were fixed by perfusion with 4% glutaraldehyde in 0.1 M cacodylate buffer. Pieces of left ventricle and interventricular septum were removed., weighed and processed for EM. The fluids used at each stage of processing were monitored for loss of radioactive lipid by scintillation counting. Lipids were extracted from the processed tissue immediately before the embedding stage using a mixture of chloroform: methanol (2:1 v/v). Counts from processed tissue were compared with counts from tissue extracted directly after perfusion fixation in order to monitor subsequent losses during processing. A modified version of Epon processing, omitting 100% ethanol, acetone or propylene oxide, gave a lipid retention of only 20.6%. The addition of para-phenylenediamine to the procedure did not improve the retention although this has been shown to be a useful stain for intracellular lipid. Water soluble Durcupan which does not involve ethanol or acetone dehydration has an average retention of 63% with 100% recovery while the lesser known polymer GACH, a mixture of glutaraldehyde and carbohydrazide used both for dehydration and embedding showed a lipid retention of 82% of the counts recovered although recovery was only 69%. An attempt was made to determine which classes of lipids were present in the tissue after perfusion fixation using thin layer chromatography. It was found that the presence of any of the processing fluids affected the polarity of the lipids and their rates of migration on thin layer plates.     

Extraction of membrane lipids during fixation,dehydration and embedding of Acholeplasma laidlawii-cells for electron microscopy

The aim of the present investigation was to study the extent to which lipids are extracted from biological membranes during dehydration and embedding procedures carried out at high or low temperatures. Cells of Acholeplasma laidlawii were used as experimental material, since the lipids of this bacterium easily can be radioactively labelled without labelling the rest of the cell, and the lipids are almost entirely located in the cytoplasmic membrane. The cells were fixed at 277 K with glutaraldehyde, sequentially with this reagent and osmium tetroxide, or with glutaraldehyde, osmium tetroxide and uranyl acetate in that order. Loss of lipid during these procedures was negligible. When cells fixed with glutaraldehyde and osmium tetroxide were dehydrated with ethanol at room temperature and embedded in Epon at 333 K, i.e. subjected to a conventional treatment, about 90% of the lipid content of the cells was extracted. The loss was reduced to c. 20% when treatment with uranyl acetate was included in the procedure and the non-polar methacrylate resin Lowicryl HM20 was substituted for Epon. When cells fixed with glutaraldehyde and osmium tetroxide were dehydrated with ethanol at 238 K and embedded in Lowicryl HM20 at room temperature, practically no lipid was extracted. Substitution of the polar methacrylate-acrylate resin Lowicryl K4M for Lowicryl HM20 resulted in the loss of about half of the lipid content of the cells. The use of ethanediol as dehydrating agent instead of ethanol did not diminish the extraction. Cells fixed solely with glutaraldehyde lost about half of their lipid content, even when both dehydration and embedding was performed at 238 K. The lipid material extracted from glutaraldehyde-fixed cells contained slightly more saturated fatty acids than that remaining in the cells. The reverse was true for osmium tetroxide-fixed cells. With respect to lipid species, the extractions were generally rather unspecific.     

Energy-filtered cryotransmission electron microscopy of liposomes prepared from human stratum corneum lipids

We used cryo-TEM to examine the morphology of vesicles formed from lipids of the human stratum corneum (hSC). Human stratum corneum lipid liposomes (hSCLLs) were prepared in buffer at various pH values, using different preparation methods (film method, extrusion, ultrasonication, detergent dialysis). The morphology of hSCLLs at pH 7.4 differed markedly from that of liposomes formed by phospholipids, showing folds, stacks and membrane thickening. At pH 5.0, corresponding to natural conditions at the skin surface, membrane structures are essentially the same as those prepared at pH 7.4. Sharp edges in hSCLLs, branching membranes and stable membrane stacks were explained by the presence of ceramides, the major components and structural elements of human stratum corneum lipids (hSCLs). Thickened areas in the membranes may be caused by the local accumulation of triacylglycerols and cholesterol esters in the hydrophobic interior of the bilayer.     

Atomic force microscopy of nanometric liposome adsorption and nanoscopic membrane domain formation

Scanning probe microscopy studies of membrane fusion and nanoscopic structures were performed using hydrated single lipids and lipid mixtures. Extruded vesicles of DMPC and mixtures at various concentrations of DLPC, DPPC and cholesterol were deposited on freshly cleaved mica and studied in a fluid environment by AFM. The nanostructures formed by these extruded liposomes ranged from isolated unilamellar vesicles to flat sheet membranes and were marked influenced by thermodynamic phase behavior. For DMPC membrane, intact bilayers exhibited a phase transition process in agreement with large bilayer patches. In the DLPC, DPPC and cholesterol mixtures, nanoscopic domain diameters ranged from approximately 25 to 48nm with height differences of approximately 1.4nm; all values were lipid composition-dependent. Our data support and extend previous studies of microscopic domains and phase boundaries of the same mixtures in giant unilamellar vesicles determined by confocal light microscopy. Our approach for preparing and utilizing supported membrane structures is potentially relevant to studies of native cell membranes.     

Tandem mass spectrometry in the study of fatty acids,bile acids,and steroids

Over the last 50 years, the mass spectrometry of lipids has evolved to become one of the most mature techniques in biomolecule analysis. Many volatile and non-polar lipids are directly amenable to analysis by gas-chromatography-mass spectrometry (GC-MS), a technique that combines the unsurpassed separation properties of gas-chromatography with the sensitivity and selectivity of electron ionization mass spectrometry. Less volatile and/or thermally labile lipids can be analyzed by GC-MS, following appropriate sample derivatization. However, many complex lipids are not readily analyzed by GC-MS, and it is these molecules that are the subject of the current review. Since the early 1970s, there have been three outstanding developments in mass spectrometry that are particularly appropriate in lipid analysis; i.e., the introduction of (i) fast atom bombardment (FAB); (ii) electrospray (ES); and (iii) tandem mass spectrometry (MS/MS). The FAB and ES ionization techniques will be discussed in relation to MS/MS, and examples of their application in biochemical studies will be presented. The review will concentrate on the analysis of fatty acids, bile acids, steroid conjugates, and neutral steroids.