Triterpene glycosides from <Emphasis Type="Italic">Astragalus</Emphasis> and their genins. LXXXIX. Askendoside H from <Emphasis Type="Italic">Astragalus taschkendicus</Emphasis>

A new triterpene glycoside of the cycloartane series that was called askendoside H was isolated from roots of Astragalus taschkendicus Bunge (Leguminosae). Its structure was elucidated based on chemical transformations and spectral data. Askendoside H was a bisdesmoside of cycloorbigenin C, 23R,24Rcycloartan-3β,6α,16β,23,24,25-hexaol 3-O-[(α-L-arabinopyranosyl)(1 → 2)-β-D-xylopyranoside] 23-O-βD-glucopyranoside.     

A UV-visible spectroelectrochemical study of the electropolymerisation of N-benzylaniline

The electropolymerisation of N-benzylaniline (NBA) at transparent ITO glass electrodes was investigated with in situ UV-visible spectroelectrochemistry. An intermediate was found to be generated during electrolysis as the precursor of poly(N-benzylaniline) (PNBA). The intermediate, which shows an absorbance band at λ = 460 nm, is able to react spontaneously with NBA, forming a polymeric end product, which is deposited on the electrode surface. UV-Vis spectra were obtained with PNBA-modified electrodes at various electrode potentials. It was shown that the colouration of the PNBA film after a positive-going potential step proceeds ca. 5 times slower than its discolouration after the reverse negative-going potential step. Anodic degradation of PNBA film was shown to proceed when holding the electrode at a sufficiently high positive potential. A linear dependence between the first-order degradation rate constant (k/s⁻¹) and electrode potential (E/V) was found in the potential range of E _RHE = +0.8 to +1.1 V: log k = a + bE, where a = −8.75 and b = 5.45 are empirical coefficients. In the whole spectral range investigated, the degradation of PNBA was found to proceed faster as compared to that of polyaniline (for polyaniline, coefficients a = −12.7 and b = 8.96 were obtained in the potential range of E _RHE = +0.85 to +1.1 V). The electrooxidation of hydroquinone, as well as the electroreduction of benzoquinone, were shown to proceed at PNBA-modified electrodes. In these processes, PNBA was shown to play the role of an electron mediator between the ITO electrode and solution phase redox species. Received: 8 January 1999 / Accepted: 27 January 1999     

Triterpene glycosides from <Emphasis Type="Italic">Astragalus</Emphasis> and their genins. XC. Askendoside K from <Emphasis Type="Italic">Astragalus taschkendicus</Emphasis>

A new triterpene cycloartane glycoside called askendoside K was isolated from roots of Astragalus taschkendicus Bunge (Leguminosae). The structure of this glycoside was established using chemical and biochemical transformations and spectral data. Askendoside K was a bisdesmoside of cycloorbigenin C and had the structure 23R,24R-cycloartan-3β,6α,16β,23,24,25-hexaol 3-O-[(α-L-arabinopyranosyl)(1 → 2)-β-D-xylopyranoside],23-O-[(β-D-glucuronopyranosyl)(1 → 2)-β-D-glucopyranoside].     

Synthesis, structures, and properties of spiro[6-azaperimidine-2,4′-cyclohexa-2′,5′-dien]-1′-one derivatives

The reaction of 5-amino-4-chloroquinolines with 4-amino-2,6-di-tert-butylphenol yielded derivatives of spiro[6-azaperimidine-2,4′-cyclohexa-2′,5′-dien]-1′-one, which exhibit photo-and thermochromic properties in solutions. The structure of 2′,6′-di-tert-butyl-5,7,9-trimethylspiro[6-aza,-2,3-dihydroperimidine-2,4′-cyclohexa-2′,5′-dien]-1′-one was established by X-ray diffraction study. The ring-chain isomerization of 2′,6′-di-tert-butyl-5,7-dimethyl-and 2′,6′-di-tert-butyl-5,7,8-trimethylspiro[6-aza-2,3-dihydroperimidine-2,4′-cyclohexa-2′,5′-dien]-1′-ones was studied by dynamic NMR spectroscopy. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2028–2034, November, 1997.     

Catalytic and Thermodynamic Characterization of Endoglucanase (CMCase) from <Emphasis Type="Italic">Aspergillus oryzae</Emphasis> cmc-1

Monomeric extracellular endoglucanase (25 kDa) of transgenic koji (Aspergillus oryzae cmc-1) produced under submerged growth condition (7.5 U mg⁻¹ protein) was purified to homogeneity level by ammonium sulfate precipitation and various column chromatography on fast protein liquid chromatography system. Activation energy for carboxymethylcellulose (CMC) hydrolysis was 3.32 kJ mol⁻¹ at optimum temperature (55 °C), and its temperature quotient (Q ₁₀) was 1.0. The enzyme was stable over a pH range of 4.1–5.3 and gave maximum activity at pH 4.4. V _max for CMC hydrolysis was 854 U mg⁻¹ protein and K _m was 20 mg CMC ml⁻¹. The turnover (k _cat) was 356 s⁻¹. The pK _a1 and pK _a2 of ionisable groups of active site controlling V _max were 3.9 and 6.25, respectively. Thermodynamic parameters for CMC hydrolysis were as follows: ΔH* = 0.59 kJ mol⁻¹, ΔG* = 64.57 kJ mol⁻¹ and ΔS* = −195.05 J mol⁻¹ K⁻¹, respectively. Activation energy for irreversible inactivation ‘E _a(d)’ of the endoglucanase was 378 kJ mol⁻¹, whereas enthalpy (ΔH*), Gibbs free energy (ΔG*) and entropy (ΔS*) of activation at 44 °C were 375.36 kJ mol⁻¹, 111.36 kJ mol⁻¹ and 833.06 J mol⁻¹ K⁻¹, respectively.     

MS–MS Fragmentation Patterns of Cholesterol Oxidation Products

Summary. This study was aimed at analyzing the daughter ion spectra of 7 toxicologically relevant cholesterol oxidation products (COPs) i.e. cholestanetriol (cholestane-3β,5α,6β-triol), 7-ketocholesterol (cholest-5-en-3β-ol-7-one), 7α-hydroxycholesterol (cholest-5-en-3β,7α-diol), 7β-hydroxycholesterol (cholest-5-en-3β,7β-diol), 25-hydroxycholesterol (cholest-5-en-3β,25-diol), α-epoxycholesterol (cholestane-5α,6α-epoxy-3β-ol) and β-epoxycholesterol (cholestane-5β,6β-epoxy-3β-ol). In addition, 19-hydroxycholesterol (cholest-5-en-3β,19-diol) was analyzed as this serves as internal standard in COPs determination by HPLC-MS. Mass spectrometry was performed using a triple quadrupol mass spectrometer that was equipped with an APCI ion source. Our results indicate a common fragmentation pattern for COPs. The main breaking sites identified were in the sterol ring system between the carbon atoms with the position numbers 11–12, 12–13, and 8–14. Typical daughter ions of m/z = 81, 95, and 195 were used for multiple reaction monitoring analysis.     

Shear induced aggregation of a pectin stabilised emulsion in two dimensions

Shear induced aggregation of a Pectin stabilised emulsion trapped at the air-liquid interface was studied in a Couette system by video enhanced microscopy. From dimension analysis, Brownian motion was identified to enhance the probability of bond formation. The characteristic time scale of aggregation was found to scale as t_c ∼ η/φ rather than t_c ∼ 1/γ˙φ as expected for orthokinetic aggregation. The structure of very large clusters showed strongly rearranged strands and fractal scaling for low γ˙ and φ, analysed by density auto-correlation. At high γ˙ and φ, the cluster was dominated by larger drops and no fractal scaling could be determined for the accessible length scales. Received: 7 June 2000 Accepted: 1 August 2000     

Structural, Spectroscopic, and Thermal Behaviour of Bis-(thiosaccharinate)-aqua-cadmium(II)

Summary.  The crystal structure of the title complex, [Cd(tsac)₂(H₂O)], has been determined by single crystal X-ray diffraction methods. It crystallizes in the monoclinic space group C2/c (a = 12.236(3), b = 8.919(3), c = 16.655(3) ?, β = 96.18(2)°, Z = 4). The molecular structure was solved from 1705 independent reflections with I > σ(I) and refined to R ₁ = 0.0489. Infrared and Raman spectra of the complex were recorded and are briefly discussed. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis. Received December 18, 2000. Accepted February 19, 2001     

A note on overpotential dependence of AC impedance data

Charge-transfer resistance [R _ct = (dη/di)_{η = 0}] and Tafel plots of current density (i) versus overpotential (η) data are generally known to yield values of the energy-transfer coefficient (α) and exchange current density (i _o) of an electrochemical reaction. In the present investigation, the resistance (dη/di)_η≠0 that could be calculated by differentiating a wide range of i−η curves was also shown to provide the values of α and i _o, by plotting ln(dη/di)_η≠0 against η. Since α and i _o could also be evaluated directly from the experimental DC polarization data, the procedure was not of significant importance. Nevertheless, it was considered important in evaluating α and i _o from AC impedance data, because the procedure was based on data analysis, which was much simpler than that reported in the literature. A cobalt electrode prepared from fine metal powder was used in 1 M KOH electrolyte and the hydrogen evolution reaction was studied by AC impedance at several potentials. The resistance values measured from the complex plane impedance diagram were plotted against the potential, and the values of α and i _o were evaluated. Received: 8 October 1998 / Accepted: 11 January 1999     

Synthesis of α-amino-β-keto-esters (β-oxodipeptides)

The synthesis of α-amino-β-keto-esters (β-oxo dipeptides) was studied. Corresponding α-amino-β-ketoesters were prepared from BOC-(L)-Valine and BOC-(L)-isoleucine by coupling with (D,L)-threonine hydrochloride and oxidation with Dess-Martin periodinane (DMP) with a total yield of 48% and 38%, respectively. __________ Translated from Chemistry Online, 2007, 70(10): 793–796 [译自: 化学通报]     

Steroidal glycosides from Allium cyrillii bulbs

Two spirostanol saponins, one of which was a new compound, were isolated among the steroidal glycosides of Allium cyrillii Ten. Bulbs. The structures of these glycosides were established using chemical and spectral analytical methods as β-D-glycopyranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 3)]-β-D-glucopyranosyl-(1 → 4)β-D-galactopyranosyl-(1 → 3)-(25R)-5α-spirostan-2α,3β-diol and β-D-glucopyranosyl-(1 → 2)-[4-O-(3hydroxy-3-methylglutaryl)-β-D-xylopyranosyl-(1 → 3)]-β-D-glucopyranosyl-(1 → 4)-β-D-galactopyranosyl(1 → 3)-(25R)-5α-spirostan-2α,3β-diol.     

Flavonoid oligosides from georgian <Emphasis Type="Italic">Astragalus falcatus</Emphasis>

New flavonoid oligosides were isolated from leaves and flowers of Astragalus falcatus Lam. It was found on the basis of chemical transformations, UV, IR, PMR, ¹³ C NMR, HMBC, HSQC, 1D-TOCSY, and mass spectral properties that falcoside C had the structure quercetin 3-O-[β-D-glucopyranosyl(1 → 3)-α-Lrhamnopyranosyl(1 → 6)]-β-D-galactopyranoside 7-O-β-D-glucopyranoside; falcoside D, isorhamnetin 3-O-[β-D-xylopyranosyl(1 → 3)-α-L-rhamnopyranosyl(1 → 6)]-β-D-galactopyranoside 7-O-α-Lrhamnopyranoside.     

Structural, Spectroscopic, and Thermal Behaviour of Bis -(thiosaccharinate)-aqua-cadmium(II)

 The crystal structure of the title complex, [Cd(tsac)₂(H₂O)], has been determined by single crystal X-ray diffraction methods. It crystallizes in the monoclinic space group C2/c (a = 12.236(3), b = 8.919(3), c = 16.655(3) ?, β = 96.18(2)°, Z = 4). The molecular structure was solved from 1705 independent reflections with I > σ(I) and refined to R ₁ = 0.0489. Infrared and Raman spectra of the complex were recorded and are briefly discussed. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis.     

A new furostanol glycoside with fatty acid synthase inhibitory activity from <Emphasis Type="Italic">Ophiopogon japonicusa</Emphasis>

A new furostanol glycoside, named ophiopogonin J (1), was isolated from the fibrous root of Ophiopogon japonicas. The structure of the compound was established as (25R)-26-[(O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyl)]-20α -hydroxyfurost-5, 22-diene-3-O-α-L-rhamnopyranosyl-(1 → 2)-[β-D-xylopyranosyl(1 → 4)]-β-D-glucopyranoside on the basis of spectroscopic methods, including HR-ESI-MS and 1D and 2D NMR experiments.     

A novel chromone-substituted trimeric dihydroflavonol from <Emphasis Type="Italic">Anogeissus pendula</Emphasis>

A new chromone-substituted dihydrotriflavonol, (2S,3S)[6-{(3S) 3″,5″-dihydroxy-6″-methoxydihydrochromone}5,3′,4′,5′-tetrahydroxy-7-methoxy-3-O-8-dihydroflavone]₂ 3-O-8[6-{(3S) 3″,5″-dihydroxy-6″methoxydihydrochromone}3,5,3′,4′,5′-pentahydroxy-7-methoxydihydroflavonol] was isolated from the leaves of Anogeissus pendula. The structure was determined by UV, ¹H NMR, ¹³C NMR, HMBC, and CD data.     

Triterpene glycosides from <Emphasis Type="Italic">Astragalus</Emphasis> and their genins. LXXX. Cyclomacroside D,a new bisdesmoside

The structure of the new cycloartane glycoside cyclomacroside D, which was isolated from Astragalus macropus Bunge (Leguminosae) and is 24R-cycloartan-1α,3β,7β,24,25-pentaol 3-O-α-L-rhamnopyranoside–24-O-β-D-xylopyranoside, was proved. Presented at the 7th International Symposium on the Chemistry of Natural Compounds (SCNC, Tashkent, Uzbekistan, October 16–18, 2007). Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 48–50, January–February, 2009.     

Electrochemical behaviors of metol on ionic-liquid-modified carbon paste electrode and its analytical application

The electrochemical behaviors of metol on an ionic liquid N-butylpyridinium hexafluorophosphate modified carbon paste electrode (IL-CPE) were studied in this paper. The results indicated that a pair of well-defined quasi-reversible redox peaks of metol appeared with the decrease of overpotential and the increase of redox peak current, which was the characteristics of electrocatalytic oxidation. The electrocatalytic mechanism was discussed and the electrochemical parameters were calculated with results of the charge-transfer coefficient (α) as 0.45, the electrode reaction rate constant (k _s) as 4.02 × 10⁻³ s⁻¹, and the diffusion coefficient (D) as 6.35 × 10⁻⁵ cm²/s. Under the optimal conditions, the anodic peak current was linear with the metol concentration in the range of 5.0 × 10⁻⁶ ∼ 1.0 × 10⁻³ mol/L (n = 11, γ = 0.994) and the detection limit was estimated as 2.33 × 10⁻⁶ mol/L (3σ). The proposed method was successfully applied to determination of metol content in synthetic samples and photographic solutions.     

Self-association and complexation of triterpene glycosides and cholesterol

Self-association of hederagenin 3-O-α-L-rhamnopyranosyl-(1→2)-O-α-L-arabinopyranoside (α-hederin) and its 28-O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl ether (hederacoside C) with cholesterol was studied using mass spectrometry (ESI MS). Possible complexation of the glycosides with cholesterol was examined. The ichtyotoxic activity of the glycosides and their mixtures with cholesterol to Barbus fefrozona was studied.     

Electrochemical solid phase micro-extraction and determination of salicylic acid from blood samples by cyclic voltammetry and differential pulse voltammetry

The electrochemical solid phase micro-extraction of salicylic acid (SA) at graphite-epoxy-composed solid electrode surface was studied by cyclic voltammetry. SA was oxidized electrochemically in pH 12.0 aqueous solution at 0.70 V (vs. saturated calomel electrode) for 7 s. The oxidized product shows two surface-controlled reversible redox couples with two proton transferred in the pH range of 1.0∼6.0 and one proton transferred in the pH range of 10.0∼13.0 and is extracted on the electrode surface with a kinetic Boltzman function of i _p = 3.473–4.499/[1 + e^{(t − 7.332)/6.123}] (χ ² = 0.00285 μA). The anodic peak current of the extracted specie in differential pulse voltammograms is proportional to the concentration of SA with regression equation of i _p = −5.913 + 0.4843 c (R = 0.995, SD = 1.6 μA) in the range of 5.00∼200 μM. The detection limit is 5.00 μM with RSD of 1.59% at 60 μM. The method is sensitive and convenient and was applied to the detection of SA in mouse blood samples with satisfactory results.     

Evaluation of a novel ELISA for serotonin: urinary serotonin as a potential biomarker for depression

Depression is a common disorder with physical and psychological manifestations often associated with low serotonin. Since noninvasive diagnostic tools for depression are sparse, we evaluated the clinical utility of a novel ELISA for the measurement of serotonin in urine from depressed subjects and from subjects under antidepressant therapy. We developed a competitive ELISA for direct measurement of serotonin in derivatized urine samples. Assay performance was evaluated and applied to clinical samples. The analytical range of the assay was from 6.7 to 425 μg serotonin/g creatinine (Cr). The limit of quantification was 4.7 μg/g Cr. The average recovery for spiked urine samples was 104.4%. Average intra-assay variation was 4.4%, and inter-assay variation was <20%. The serotonin analysis was very specific. No significant interferences were observed for 44 structurally and nonstructurally related urinary substances. Very good correlation was observed between urinary serotonin levels measured by ELISA and liquid chromatography tandem mass spectrometry (LC-MS/MS; ELISA = 1.16 × LC-MS/MS − 53.8; r = 0.965; mean % bias = 11%; n = 18). Serotonin was stable in acidified urine for 30 days at room temperature and at −20 °C. The established reference range for serotonin was 54–366 μg/g Cr (n = 64). Serotonin levels detected in depressed patients (87.53 ± 4.89 μg/g Cr; n = 60) were significantly lower (p < 0.001) than in nondepressed subjects (153.38 ± 7.99 μg/g Cr). Urinary excretion of serotonin in depressed individuals significantly increased after antidepressant treatment by 5-hydroxy-tryptophane and/or selective serotonin re-uptake inhibitor (p < 0.01). The present ELISA provides a convenient and robust method for monitoring urinary serotonin. It is suitable to monitor serotonin imbalances and may be particularly helpful in evaluating antidepressant therapies.