Electrodimerization of cyano-substituted derivatives of anthracene and naphthalene

The electrochemistry of cyano-substituted derivatives of naphthalene and anthracene was studied at different temperatures (298–233 K) using slow and fast scan voltammetry with a maximum scan rate of 500 V s⁻¹. All experimental evidence indicates the formation of a dimer by an E_revC_2rev process at the monoanion level. Rate constants for dimerization process were evaluated in six different polar solvents using theoretical working curves for an E_revC_2rev mechanism. Digital simulation was used to verify the accuracy of these rate constants. The results show that the polarity of the solvent influences the rate of dimerization reactions and that radical anions of the studied compounds dimerize under diffusion control.     

Electrodimerization of crotonic aldehyde in aqueous media on a mercury electrode

The electrohydrodimerization mechanism of crotonaldehyde reduction on a mercury electrode is characterized on the basis of polarographic (dc and DP) and voltammetric experiments and determination of reaction orders. The possibilities of the differential pulse polarographic technique in discriminating between the different electrodimerization processes are mentioned.     

Determination of trigonelline in green and roasted coffee from single column ionic chromatography

Trigonelline can be determined in green and roasted coffee extracts by a ion chromatographic method on a single column filled with polybutadiene-maleic acid (PBDMA) coated on silicia, 2 mmol/L aqueous HCl (pH 3) as eluent and UV detection at 254 nm. The merits of the new method are investigated. Received: 22 February 1996 / Revised: 15 April 1996 / Accepted: 18 April 1996     

Electrodimerization: Part XII. Coupling mechanism of activated olefins at preparative scale concentrations

Previous studies have shown that the electrohydrodimerization mechanism of activated olefins is of the radical-radical coupling type in the millimolar range. The present work attempts to determine the mechanism up to the decimolar range on the particular example of p-methyl-benzylidene-malononitrile (MBM) in DMF. The kinetics of the system are studied using chronopotentiometry. The corrections of ohmic drop and double-layer charging and the conditions in which sphericity and migration of the reactants may be neglected are discussed first and experimentally tested on the fluorenone/fluorenone anion system. It is concluded from the kinetic analysis of the MBM reduction that the radical-radical nature of the coupling step does not change when passing from the millimolar to the decimolar level. The residual water is shown to play an important role in the overall reaction, the formation of an anion radical-water adduct being an essential step.     

亲水作用色谱法测定胡芦巴中的胡芦巴碱

建立了亲水作用色谱法(HILIC)测定胡芦巴药材中胡芦巴碱含量的方法。采用Waters Atlantis HILIC Silica色谱柱(150 mm×2.1 mm, 3 μm),以乙腈-乙酸铵溶液(pH 4.4)(体积比为70:30)为流动相,流速0.4 mL/min,检测波长265 nm。胡芦巴碱的线性范围为2.50～100 mg/L (r=0.9996);两个加标水平的平均加样回收率为102%,相对标准偏差(RSD)分别为4.17%和2.28%(n=3)。结果表明所建方法分离效果好、快速简易,可以弥补中国药典中离子对色谱法(IPLC)平衡时间过长的缺陷,适用于胡芦巴药材中强极性胡芦巴碱的测定,为胡芦巴的质量控制提供了有效的方法。     

Simple, sensitive, selective and validated spectrophotometric methods for the estimation of a biomarker trigonelline from polyherbal gels

Simple, accurate, reproducible, selective, sensitive and cost effective UV-spectrophotometric methods were developed and validated for the estimation of trigonelline in bulk and pharmaceutical formulations. Trigonelline was estimated at 265 nm in deionised water and at 264 nm in phosphate buffer (pH 4.5). Beer's law was obeyed in the concentration ranges of 1-20microg mL(-1) (r2=0.9999) in deionised water and 1-24 microg mL(-1) (r2=0.9999) in the phosphate buffer medium. The apparent molar absorptivity and Sandell's sensitivity coefficient were found to be 4.04 x 10(3)L mol(-1)cm(-1) and 0.0422 microg cm(-2)/0.001A in deionised water; and 3.05 x 10(3)L mol(-1)cm(-1) and 0.0567 microg cm(-2)/0.001A in phosphate buffer media, respectively. These methods were tested and validated for various parameters according to ICH guidelines. The detection and quantitation limits were found to be 0.12 and 0.37 microg mL(-1) in deionised water and 0.13 and 0.40 microg mL(-1) in phosphate buffer medium, respectively. The proposed methods were successfully applied for the determination of trigonelline in pharmaceutical formulations (vaginal tablets and bioadhesive vaginal gels). The results demonstrated that the procedure is accurate, precise, specific and reproducible (percent relative standard deviation <2%), while being simple and less time consuming and hence can be suitably applied for the estimation of trigonelline in different dosage forms and dissolution studies.     

Selective determination of caffeine and trigonelline in aqueous extract of green coffee beans by FT-MIR-ATR spectroscopy

A non-destructive, fast, simple and reliable Fourier transform mid-infrared attenuated total reflectance spectroscopy (FT-MIR-ATR) method for the selective determination of caffeine and trigonelline in the aqueous extract of green coffee beans was developed and validated. The calibration curves were linear in the range 2000 − 7000 mg/L for caffeine and trigonelline with R² ≥ 0.9997. The limits of detection (LOD) were 140 and 100 mg/L and the limits of quantification (LOQ) were 470 and 330 mg/L for caffeine and trigonelline, respectively. The precision (% RSD) was 3.0% and 4.3% for caffeine and trigonelline, respectively. The developed method was applied to 20 samples of green coffee beans to determine the two alkaloids. The amount of caffeine and trigonelline in the green coffee beans were found in the range 0.84 − 1.15% (w/w) and 0.83 − 1.13% (w/w), respectively. The accuracy of the developed analytical method was evaluated by spiking standard caffeine and trigonelline to green coffee beans and the average recoveries were 93 ± 5% and 98 ± 4%, respectively. Therefore, the developed FT-MIR-ATR methods can be used for direct determination of the two alkaloids in the green coffee beans.     

超声波萃取-高效液相色谱测定咖啡粉和速溶咖啡中的葫芦巴碱

建立了高效液相色谱测定咖啡粉和速溶咖啡中葫芦巴碱含量的方法。采用Waters BondPak NH2色谱柱(250 mm×4.6 mm, 5 μm),以甲醇-水(82:18, v/v)为流动相,流速0.8 mL/min,检测波长260 nm。葫芦巴碱线性范围为1～40 mg/L (相关系数为0.9998)。分别进行日内、日间和人员比对测定葫芦巴碱的重复性试验及加标回收率试验。经测定,样品的加标回收率大于90%,相对标准偏差小于3%。比较了超声波萃取和热浸提萃取方法测定葫芦巴碱含量的差异,两个方法的测定结果符合线性关系,相关系数为0.9964。该法简便、快速、灵敏度高,适用于咖啡豆中葫芦巴碱分析以及咖啡豆原料与制品的质量控制。     

Validated high-performance thin-layer chromatography method for determination of trigonelline in herbal extract and pharmaceutical dosage form

A new, simple, sensitive, selective, precise and robust high-performance thin-layer chromatographic (HPTLC) method for analysis of trigonelline was developed and validated for the determination of trigonelline in herbal extracts and in pharmaceutical dosage forms. Analysis of trigonelline was performed on TLC aluminium plates pre-coated with silica gel 60F-254 as the stationary phase. Linear ascending development was carried out in twin trough glass chamber saturated with mobile phase consisting of n-propanol-methanol-water (4:1:4, v/v/v) at room temperature (25 ± 2 °C). Camag TLC scanner III was used for spectrodensitometric scanning and analysis in absorbance mode at 269 nm. The system was found to give compact spots for trigonelline (R_f value of 0.46 ± 0.02). The linear regression analysis data for the calibration plots showed good linear relationship with r² = 0.9991 ± 0.0002 in the concentration range 100-1200 ng spot⁻¹ with respect to peak area. According to the International Conference on Harmonization (ICH) guidelines the method was validated for precision, recovery, robustness and ruggedness. The limits of detection and quantification were determined. The trigonelline content of herbal extracts quantified and estimated from the formulation was found to be well within limits (±5% of the labeled content of the formulations). Statistical analysis of the data showed that the method is reproducible and selective for the estimation of trigonelline.     

Pyridine metabolism and trigonelline synthesis in leaves of the mangrove legume trees Derris indica (Millettia pinnata) and Caesalpinia crista

The aim of this study was to reveal the pyridine metabolism in leaves of two mangrove legumes, Derris indica (= Millettia pinnata or Pongamia pinnata) and Caesalpinia crista. Radioactivity from [carbonyl-14C]nicotinamide supplied exogenously to young leaf disks was recovered in nicotinic acid, nicotinic acid mononucleotide, NAD, NADP, nicotinamide mononucleotide and trigonelline. These mangrove species, especially D. indica, have strong ability to convert nicotinamide to trigonelline, but not to nicotinic acid glucoside. The endogenous trigonelline content in leaves of D. indica was more than 830 microg/g dry weight. This value is 5-12 times greater than that in leaves of Glycine max. There was little short-term effect of 250 and 500 mM NaCl (equivalent to ca. 50% and 100% sea water) on nicotinamide metabolism.     

High-performance thin-layer chromatographic determination of trigonelline content in various extracts and different varieties of some commercial coffees available in the Saudi Arabian market

JPC – Journal of Planar Chromatography – Modern TLC - The proposed research study was undertaken to establish a simple, rapid and sensitive high-performance thin-layer chromatography...     

Effect of acids and bases on the solubility of amino acids

The effect of acids and bases on the solubility of amino acids at 298.2 K, within the pH range, (pH from 2 to 10) and out of the pH range, was determined. The amino acids considered were glycine, dl-alanine, dl-valine and dl-serine. The acids used were HCl and HNO₃ and the bases NaOH and KOH. It was observed that in the pH range (pH from 2 to 10) there is no significant difference in the solubility of dl-alanine in the presence of different ions such as Na⁺ or K⁺ at high pH, and Cl⁻ or NO₃⁻ at low pH values. However, at higher concentrations of the acids or the bases, there is an effect of the counterions in solubilities. For all the amino acids considered here the solubility was higher in nitric acid, as compared to hydrochloric acid, and higher in potassium hydroxide than in sodium hydroxide.     

Voltammetric study of the interaction of ciprofloxacin-copper with nucleic acids and the determination of nucleic acids

The behavior of the ciprofloxacin (CPFX) complex with copper, Cu(II)L₂, at a mercury electrode has been investigated in borax–boric acid buffer. The adsorption phenomena were observed by linear sweep voltammetry. The mechanism of the electrode reaction was found to be reduction of Cu(II)L₂ adsorbed on the surface of the electrode by an irreversible charge transfer to metal amalgam, Cu(0)(Hg). In the presence of DNA, the formation of the electrochemically non-active complexes Cu(II)L₂–DNA results in the decrease of the equilibrium concentration of Cu(II)L₂ and its peak current. Under the optimum conditions, the decrease of the peak current is proportional to DNA concentration. The linear ranges are 6.67×10⁻⁸ to 1.20×10⁻⁵ g ml⁻¹ for calf thymus DNA (ctDNA), 3.30×10⁻⁸ to 2.33×10⁻⁶ g ml⁻¹ for fish sperm DNA (fsDNA) and 1.0×10⁻⁸ to 1.2×10⁻⁶ g ml⁻¹ for yeast RNA. The detection limits are 5.00×10⁻⁹, 3.00×10⁻⁹ and 2.50×10⁻⁹ g ml⁻¹, respectively. This method exhibits good recovery and high sensitivity.     

Chemistry and biology of the acylneuraminic acids

Acylneuraminic acids occupy an outstanding position both sterically and with respect to biological functions in gangliosides and in many glycoprotein molecules. Acylneuraminic acids are N-acylated and partly O-acylated derivatives of neuraminic acid, a polyhydroxyamino keto acid that has the properties of a carbohydrate and is therefore capable of forming a glycoside linkage. The present report provides a survey of our knowledge of the chemistry and biology of the acylneuraminic acids, which occur widely in particular in the animal kingdom.     

Paper chromatography of fatty acids and halogenated organic acids

A paper chromatographic method is described for the identification of the volatile fatty acids and some of their bromo- and iodo-derivatives. Some new spraying reagents are suggested which enable the different classes of acids to be detected in presence of one another.     

Determination of trigonelline, nicotinic acid, and caffeine in Yunnan Arabica coffee by microwave-assisted extraction and HPLC with two columns in series

A simple, rapid method was developed for simultaneous extraction of trigonelline, nicotinic acid, and caffeine from coffee, and separation by two chromatographic columns in series. The trigonelline, nicotinic acid, and caffeine were extracted with microwave-assisted extraction (MAE). The optimal conditions selected were 3 min, 200 psi, and 120 degrees C. The chromatographic separation was performed with two columns in series, polyaromatic hydrocarbon C18 (250 x 4.6 mm id, 5 microm particle size) and Bondapak NH2 (300 x 3.9 mm id, 5 microm particle size). Isocratic elution was with 0.02 M phosphoric acid-methanol (70 + 30, v/v) mobile phase at a flow rate of 0.8 mL/min. Good recoveries and RSD values were found for all analytes in the matrix. The LOD of the three compounds was 0.02 mg/L, and the LOQ was 0.005% in the matrix. The concentrations of trigonelline, nicotinic acid, and caffeine in instant coffee, roasted coffee, and raw coffee (Yunnan Arabica coffee) were assessed by MAE and hot water extraction; the correlation coefficients between concentrations of the three compounds obtained were close to 1.     

冠醚酮酸和烷酸的合成

本文介绍了在PPA存在下，由B15C5和DB18C6同过量的二羧酸发生酰化作用，得到酮酸1a～e和3a～c。再把所得相应的酮酸1a～e和3a～c利用黄鸣龙法制得4'-(ω－羧基多亚甲基)苯并-15-冠-5(2a～e)和4',4'(5')-二(ω-羧基多亚甲基)二苯并-18-冠-6(4a～c)等一系列ω-冠醚酮酸。