若干天然糖苷类的快原子轰击质谱及快原子轰击碰撞活化质量分析离子动能谱研究

糖苷类化合物因为极性大和热不稳定而难以用通常的电子轰击电离质谱进行结构测定。我们用FAB-MS和FAB-CA-MIKES对这类化合物进行了结构研究,不仅获得了准确的分子量和苷元碎片,还获得了糖的序列以及糖本身的裂解途径等重要结构信息。     

松三糖衍生物的快原子轰击质谱分析

1引言快原子轰击质谱在糖化学领域有广泛的应用,但涉及松三糖的研究却未见报道.松三糖是一种非还原性糖,是具有独特药用价值刺糖的主要成分?我们在研究松三糖羟基反应活性与结构的关系时,制备得到了一系列未见文献报道的松三糖衍生物,在用快原子轰击质谱(MS-FAB)研究它们的结构时.发现其中两个同为十-0-乙酰基松三糖的样品的裂解碎片有明显的差异,进一步研究发现它们是一对位置异构体,证实它们的差别在于其游离羟基分别位于果糖环的C-4位和C-6位?2实验邪分二.且仪器和实验条件ZAB-HS质谱仪门G公司),扫描范围2000p-200p,扫描速度20sjd,…     

快原子轰击和碰撞活化质谱法研究三萜皂苷结构

本文用快原子轰击(FAB)和碰撞活化(CA)相配合的方法测定了含3-5个糖基的三萜皂苷的结构.FAB谱能给出分子量信息,由质子化分子的CA谱可推测糖基连接序列.本法的优点在于难挥发,热不稳定的样品可直接进样分析不需制成挥发性衍生物,且样品中杂质经磁场进行质量分离后影响CA谱.本法的局限性在于不能区别糖的立体异构体和确定各糖基或糖基与苷元的连接位置.     

暗霉素的快原子轰击(FAB)质谱

快原子轰击(fast atom bombardment,简称 FAR)质谱是八十年代开发的质谱新技术.这种在室温条件下用具有一定能量的中性原子轰击样品进行离子化的技术特别适用予热稳定性差、难挥发、强极性样品的分析.我们用 FAB 对七个暗霉素(nebramycin)抗生素组分进行结构测定,获得了较满意的结果.暗霉素属氨基糖苷类抗生素.我们从我国土壤中分离的菌株发酵液中提取暗霉素复合物及其水解产物,并分离和鉴定了七个单一组分.这七个化合物(1～7)的结构如下:     

糖类化合物的快原子轰击质谱研究

人类在探索生命科学的进程中,对糖、蛋白质及核酸这三类基本生命物质的研究日益深入。近年来,随着分子生物学特别是细胞生物学的高速发展,糖类化合物在生命科学中所起的作用也得到了高度重视。糖不仅作为能量物质(葡萄糖、淀粉、糖原)和结构物质(几丁质、纤维素)为人们所熟知,它的其它诸多生理、生化功能,如携带和传递生物信息,调节细胞的生长发育、分化代谢及免疫反应等,均逐渐被掲示和认识。     

快原子轰击质谱

电子轰击、化学电离和场电离质谱由于要求样品在电离前气化,不适于分析极性高的热不稳定化合物。场解吸电离法的出现扩大了质谱的应用范围。现在,场解吸电离法与高场强度磁铁配合,可以分析分子量为3000的化合物。但是应当指出,场解吸电离法还是有局限性的。用场解吸法得到的谱图随分析时间改变,重现性差;实验操作难度大,不容易掌握;碎片离子峰少,提供的结构信息少;解吸需要一定的加热电流,从而使一些化合物发生热分解;对于一些极性特别大的化合物,场解吸法也无能为力。     

双冠醚的快原子轰击质谱

近年来不断有合成新冠醚和冠醚衍生物的报道,关于冠醚质谱特征的研究也开始见诸文献,但这类文献的报道还不多.这可能是因为冠醚,尤其是复杂冠醚衍生物的熔点较高,在电子轰击(EI)或化学电离(CI)条件下测定存在一定困难的缘故.例如,本文讨论的双冠醚1～4都曾用EI法进行质谱测定.测定时,样品需加热到350℃,甚至400℃以上,才能得到质谱信号,而所得信号仍然相当弱.这不仅是测定本身的困难,而且可能引起离子源污染等问题.为此,我们采用快原子轰击(FAB)法测定双冠醚1～6的质谱,并对其裂解规律进行了初步的探讨.     

含酯糖链皂甙的负离子快原子轰击质谱分析

本实验用负离子快原子轰击(FAB)法测定了8个含酯糖链的双糖链皂甙样品,给出了明显的脱质子分子离子峰,由碎片离子峰可推测糖基的连接顺序;不仅对难挥发、热不稳定和极性大的样品可直接进样分析,而且对在酯糖链皂甙中出现以酯裂解为基峰的碎片,还可初步确定糖链在甙元上的连接位置。     

寡糖快原子轰击质谱中碱金属加合离子应用技术的研究

生命科学的研究成果^[1～3]表明,糖蛋白和糖脂中的糖基可作为细胞的识别信号,能控制细胞的分裂和分化.快原子轰击(FAB)质谱是测定寡糖的重要手段^[4,5],但目前还存在不少问题.我们在对麦芽各糖的研究中.     

快原子轰击离子化质谱研究酚类化合物抗氧化作用

为了建立简便、快速筛选高效、低毒的新型抗氧化药物的方法,本研究采用快原子轰击离子化质谱( FAB-MS)对酚类化合物抗氧化作用强弱进行了研究。考察了基质、轰击时间和样本浓度对FAB-MS 谱中分子离子(M+·)相对强度的影响,研究了黄酮类化合物在FAB-MS谱中的I(M+·)/I([M+H]+)比值与其抗氧化活性的相关性。对12种酚类化合物的抗氧化活性进行了预测与评价,并与硫代巴比妥酸法( TBA)检测的脂质过氧化抑制率进行比较,验证 FAB-MS 方法的可靠性。结果表明,由 FAB-MS 获得的 I ( M+·)/I([ M+H]+)比值能较好地反映酚类化合物抗氧化作用的强弱,可以作为抗氧化剂的体外筛选或预测方法,有助于加速新型抗氧化药物的发现。     

Two new flavanonol glycosides from Gordonia chrysandra

Two new flavanonol glycosides named chrysandrosides A and B were isolated from the roots of Gordonia chrysandra Cowan. Their structures were determined by 1D and 2D NMR, FAB-MS techniques and chemical methods. Chrysandrosides A and B showed pronounced hepatoprotective activities against o-galactosamine （o-GalN）-induced toxicity in rat hepatic epithelial stemlike cells （WB-F344）. 2007 Dong Ming Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Two New Chromone Glycosides from Selaginella uncinata

Two new chromone glycosides,5-hydroxy-2,6,8-trimethylchromon-7-O-β-D-gluco-pyranoside,named uncinoside A;5-acetoxy-2,6,8-trimethylchromone-7-O-β-D-glucopyranoside, named uncinoside B,and a known chromone compound named 8-methyl eugenitol were isolated from Selaginella uncinate. Their structures were elucidated by spectra analysis of FAB-MS,1D NMR and 2D NMR including ^1H NMR,^13C NMR,HMQC,HMBC and single-crystal X-ray diffraction techniques.     

Cycloartane glycosides from Cimicifuga dahurica.

A new cycloartane bisdesmoside and two new trinorcycloartane glycosides, along with four known cycloartane compounds, were isolated from the rhizomes of Cimicifuga dahurica (Ranunculaceae). The structures of the new compounds were elucidated as 3-O-alpha-L-arabinopyranosyl cimigenol 15-O-beta-D-glucopyranoside, 24-hydroxy-12beta-acetoxy-25,26,27-trinorcycloartan-16,23-dione 3beta-O-alpha-L-arabinopyranoside, and 16alpha,24alpha-dihydroxy-12beta acetoxy-25,26,27-trinor-16,24-cyclocycloartan-23-one 3beta-O-alpha-L-arabinopyranoside by extensive NMR methods, FAB-MS, and hydrolysis.     

Rapid resolution of carbohydrate isomers by electrospray ionization ambient pressure ion mobility spectrometry-time-of-flight mass spectrometry (ESI-APIMS-TOFMS)

Carbohydrates are an extremely complex group of isomeric molecules that have been difficult to analyze in the gas phase by mass spectrometry because (1) precursor ions and product ions to successive stages of MS(n) are frequently mixtures of isomers, and (2) detailed information about the anomeric configuration and location of specific stereochemical variants of monosaccharides within larger molecules has not been possible to obtain in a general way. Herein, it is demonstrated that gas-phase analyses by direct combination of electrospray ionization, ambient pressure ion mobility spectrometry, and time-of-flight mass spectrometry (ESI-APIMS-TOFMS) provides sufficient resolution to separate different anomeric methyl glycosides and to separate different stereoisomeric methyl glycosides having the same anomeric configuration. Reducing sugars were typically resolved into more than one peak, which might represent separation of cyclic species having different anomeric configurations and/or ring forms. The extent of separation, both with methyl glycosides and reducing sugars, was significantly affected by the nature of the drift gas and by the nature of an adducting metal ion or ion complex. The study demonstrated that ESI-APIMS-TOFMS is a rapid and effective analytical technique for the separation of isomeric methyl glycosides and simple sugars, and can be used to differentiate glycosides having different anomeric configurations.     

Four Novel Glycosides from the Aphid Pseudoregma bambmicola T

Four novel glycosides, bambusicolasides III–VI ( 1 – 4 ), were isolated from the aphid Pseudoregma bambusicola T. The structures of 1 – 4 were elucidated by spectral evidence including FAB-MS and C.H-COSY, HMBC, and NOE difference experiments, and by hydrolysis. In vitro tests with these compounds showed little cytotoxic activity against human KB cells (< 10%).     

Cardiac glycosides and pregnanes from Adenium obesum (studies on the constituents of Adenium. I)

Cardiac glycosides and pregnanes from the roots and the stems of Adenium obesum Roem. et Schult. were investigated. Among 30 cardiac glycosides including 15 known glycosides and 15 new combinations of the known aglycones and sugars, the structures of 11 glycosides were elucidated. Oleandrigenin beta-gentiobiosyl-beta-D-thevetoside was the main glycoside. Neridienone A and 16,17-dihydroneridienone A, common pregnanes in Apocynaceae, were also isolated.     

Synthesis of Indole Derivatives from 2-Keto Glycoside

2-Oxo derivatives of glycosides, called 2-keto glycosides or glycoside 2-uloses, are biologically important in carbohydrate metabolism and are very useful in synthesis of branched-chain sugars and amino sugars. Very little is known of their chemistry because of the high susceptibility of these compounds to degradation in solution, and in particular their instability to base. Thus it is important to study the reactivities of 2-keto glycosides. In a previous paper, we reported the transformation of 2-keto glycosides in pyridine solution. During the transformation of 2-and 3-keto glycosides, a demethoxylation reaction of the enol intermediate was shown to take place simultaneously with elimination to give hex-1-enopyran-3-ulose.     

Total Synthesis of L-Oleandrose and L-Cymarose from an Achiral Precursor, Methyl Sorbata

Rare monosaccharides are important structural components of antibiotics and cardiac glycosides1,2, and functionalized monosaccharides continue to be of interest as intermediates in natural product synthesis3,4. The 2,6-dideoxy sugar L-oleandrose 1 occurs …     

Synthesis and mycobacterial growth inhibition activities of bivalent and monovalent arabinofuranoside containing alkyl glycosides

Arabinofuranosides constitute one of the important components of cell wall structures of mycobacteria. With this importance of arabinofuranosides in mind, alkyl glycosides bearing arabinofuranoside trisaccharides were prepared, wherein the sugars were presented either in the monovalent or bivalent forms. Following the synthesis, the monovalent and bivalent alkyl glycosides were tested for their activities in a mycobacterial growth assay. The growth of the mycobacterial strain M. smegmatis was assessed in the presence of the alkyl glycosides and it was realized that the alkyl glycosides acted as inhibitors of the mycobacterial growth. The inhibition of the growth, caused by the above alkyl glycosides, was not observed for the arabinofuranose trisaccharide alone, without the alkyl groups, and for an alkyl glycoside bearing maltose as the sugar component.     

七叶一枝花中薯蓣皂苷的分离及结构鉴定研究

本文利用高效液相色谱-串联质谱联用方法研究了七叶一枝花中的薯蓣皂苷。实验采用高效液相色谱分离了七叶一枝花中的3种薯蓣皂苷;通过与电喷雾质谱联用获得了这几种化合物的分子量信息;再用MS/MS获得了这几种化合物进一步的结构信息。采用此方法可快速分析鉴定从七叶一枝花中分离得到的薯蓣皂苷。