反相高效液相色谱法测定山楂中的有机酸

采用Hypersil ODS2(4.6 mm×250 mm,5μm)色谱柱,以磷酸盐缓冲溶液(pH=2.6)为流动相,流速0.8 mL/m in,检测波长210 nm,建立了山楂中柠檬酸、苹果酸等有机酸的高效液相色谱分析方法。其中柠檬酸和苹果酸的线性范围分别为0.50~50.04μg、0.10~10.00μg;3个浓度水平的回收率分别为95.5%~96.6%、100.2%~103.7%,RSD分别为0.11%~0.38%、0.41%~2.53%;检出限分别为0.04μg、0.03μg(S/N=3)。测定了5种不同产地山楂果肉及山楂核中的柠檬酸、苹果酸的含量。所建立的方法快速、灵敏度高、重复性好,可用于山楂中有机酸的测定。     

山楂果实中主要活性物质的高效液相色谱分析

山楂提取物具有抗氧化、清除自由基等作用。多数学者认为,黄酮和低聚前花青素是山楂提取物的两类主要活性物质。用高效液相色谱法(HPLC)对其进行分析的报道较多,但是到目前为止尚未见到能同时分析这些成分的令人满意的方法。本文建立了一种能同时分析山楂果实中这些活性成分的HPLC方法。     

山楂红色素的研究

报道山楂红色素最稳定的ｐＨ值范围和受高温加热及强光照射时的变化，以及一些金属离子、有机酸、无机酸、糖类等食品中常见共存物质对山楂红色素稳定性的影响。     

高效液相色谱-飞行时间质谱联用法分析人参及人参皂苷与山楂配伍过程中的水解行为

利用高效液相色谱-飞行时间质谱联用的方法,分别对人参配伍山楂前后人参皂苷的变化进行分析,同时对人参皂苷Re、Rg1、Rb1、Rd与山楂配伍的水解规律进行系统研究,并与单独煎煮液、仿山楂配伍pH值煎煮液的水解产物进行比较,结果发现人参与山楂配伍后人参皂苷Rg1、Rb1含量明显减少,而人参皂苷Re、Rd、Rg2、Rg3、F2、Rh1含量明显增加,其中人参皂苷Re与山楂配伍后水解产物为人参皂苷20(R)-Rg2、20(S)-Rg2,仿山楂配伍pH值水解产物为人参皂苷20(R)-Rg2、20(S)-Rg2、Rg4、Rg6;人参皂苷Rg1与山楂配伍后水解产物为20(S)-Rh1、20(R)-Rh1,仿山楂pH值水解产物为20(S)-Rh1、20(R)-Rh1、Rh4、Rk3;人参皂苷Rb1与山楂配伍后水解产物为Rd、20(S)-Rg3,仿山楂pH值水解产物为F2、20(S)-Rg3;人参皂苷Rd与山楂配伍后水解产物为F2、20(S)-Rg3、20(R)-Rg3,仿山楂pH值水解产物为20(S)-Rg3、20(R)-Rg3。研究表明,不同人参皂苷和山楂配伍后与仿山楂pH值的水解产物并不相同,人参与山楂配伍改变了人参皂苷成分的种类及含量。本研究为临床方剂中人参与山楂配伍后成分的变化提供物质基础数据。     

基于超高效液相色谱串联质谱法的化学计量学分析不同产区烤烟烟叶中非挥发性有机酸的含量差异北大核心CSCD

非挥发性有机酸成分对烤烟的感官特征有显著影响,为研究不同产区烤烟烟叶中非挥发性有机酸含量差异及与感官特征之间的联系,采用超高效液相色谱串联质谱法(UHPLC-MS/MS)对黑龙江、四川、湖南、湖北、云南等5个不同产区烤烟样品中非挥发性有机酸成分进行了检测。通过正交偏最小二乘判别分析(OPLS-DA)模型、变量投影重要性(VIP)值、单因素方差分析(ANOVA)、京都基因和基因组数据库(KEGG)富集通路分析,得出了不同产区间非挥发性有机酸差异,并确定了特征差异组分的代谢通路。结果表明:共检测到69种非挥发性有机酸,其中多元酸23种,游离脂肪酸21种,其他有机酸25种。基于非挥发性有机酸构建的OPLS-DA模型对不同产区烟叶识别效果较理想,模型参数R^(2)Y和Q^(2)分别为0.931和0.595。通过模型的VIP值和ANOVA筛选出26种特征差异非挥发性有机酸,并通过KEGG富集分析得到16条与上述26种组分关联的代谢通路。研究发现黑龙江牡丹江产区烟叶中特征差异非挥发性有机酸含量与其他产区差异最大,其次为湖南衡阳产区,四川凉山、云南楚雄、湖北恩施产区烟叶中特征差异非挥发性有机酸组间差异较小,均与所属烟区烤烟感官特征相符。     

顶空固相微萃取-气相色谱-质谱分析发酵香肠挥发性成分

采用固相微萃取-气相色谱-质谱(SPME-GC-MS)联用分析技术对发酵香肠挥发性成分进行了分析。共鉴定了33种化合物。结果表明，发酵香肠的挥发性成分主要为醇类、酮类、酯类、有机酸类、酚类及醛类等。     

山楂汁树脂柱层析过程中主要有机酸变化规律探讨

利用高效液相色谱法测定山楂汁经过树脂柱层析处理后流出液中草酸、酒石酸、苹果酸、柠檬酸、琥珀酸5种单一有机酸含量,探讨山楂汁中主要有机酸在树脂吸附与解吸附过程中的变化规律,为降酸后果汁口感的改变原因提供依据。5种有机酸达到饱和的先后顺序:琥珀酸,草酸,苹果酸,酒石酸,柠檬酸;吸附过程中5种有机酸总含量与总滴定酸含量分别降低26.71%和40.54%;在吸附阶段,有机酸对树脂吸附位点存在竞争性,出现柠檬酸作为洗脱液将其他有机酸洗脱的现象;由于不完全解吸附,树脂吸附能力随树脂柱层析次数的增加而降低。     

ZIF-8对金银花叶中有机酸的选择性吸附：实验和理论研究（英文）

建立一种有效的制备、分离、纯化金银花叶中有机酸的方法很具有挑战性。以ZIF-8号为吸附剂,从金银花叶中选择性吸附分离有机酸,并对吸附机理进行了研究。考察了吸附剂用量、吸附时间、吸附温度和解吸条件等主要参数。在最佳条件下,ZIF-8富集的成分主要是有机酸(新绿原酸、绿原酸、咖啡酸、异绿原酸B、异绿原酸A和异绿原酸C)。ZIF-8对这6种化合物在三个加标水平(0.5、5、10 mg·L~(-1))下的回收率在70.7%～107.7%,相对标准偏差在0.89%～7.57%之间。此外,我们认为ZIF-8对有机酸的吸附主要归因于表面吸附、静电和氢键相互作用。这些结果证明了MOFs材料从复杂药用植物中选择性提取活性成分的可行性。     

中药中有机酸成分快速甲酯化方法的研究

以中药材猫爪草为分析对象,研究了简便快速分析中药中有机酸成分的方法。方法以10%硫酸甲醇-苯(1∶1)溶液为甲酯化试剂,利用微波辅助直接甲酯化药材,在微波功率600W、压力0.2MPa的条件下,反应1min即完成对药材中有机酸的甲酯化;采用气相色谱-质谱(GC-MS)联用技术进行分析,检出有23个色谱峰;经NIST2000标准谱库检索,识别了18种有机酸(占总峰面积的96.79%),并用对照品进行了验证。对不同来源的猫爪草药材进行分析,检出有20个共有峰,经方法学验证,符合指纹图谱的检测要求。     

气相色谱-质谱联用法分析烟丝中有机酸成分

采用三氟化硼和甲醇对西湖香烟烟丝样品进行衍生化反应，以二氯甲烷为萃取液，得到烟丝样品有机酸甲酯成分，在GC/MX气相色谱/质谱联用仪上定性和定量分析，共鉴定出有机酸41种，主要成分依次为苹果酸、柠檬酸、亚麻酸。实验表明分析方法简便、快速，结果令人满意。     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.