Pulse radiolysis study of rapid electron transfer from electron adduct and reducing OH adduct of dAMP to riboflavin and flavin adenine dinucleotide (FAD)

Rapid electron transfer from electron adduct and reducing OH adduct of 2'-deoxyadenosine-5'-monophosphate acid (dAMP) to riboflavin (RF) and flavin adenine dinudeotide (FAD) was studied using the time-resolved pulse radiolysLs techniques. Both spectroscopic and kinetic analyses showed that transient absorption spectrum of electron adduct or OH adduct of dAMP formed at first, and then changed to that of radical anion of RF or FAD after several microseconds of pulse. The evidence indicated that electron transfer from electron adduct and reducing OH adduct of dAMP to RF or FAD did occur. From buildup or bleaching kinetics of radical anions of RF and FAD, the rate constants for electron transfer were determined, respectively.     

Radical scavenging reactions of chlorogenic acid: A pulse radiolysis study

At near neutral pH (approx. 5.5), the OH-adduct of chlorogenic acid (CGA), formed on pulse radiolysis of N₂O-saturated aqueous CGA solutions (λ _max = 400 and 450 nm) with k = 9 × 10⁹ dm³ mol⁻¹ s⁻¹, rapidly eliminates water (k = 1 × 10³ s⁻¹) to give a resonance-stabilized phenoxyl type of radical. Oxygen rapidly adds to the OH-adduct of CGA (pH 5.5) to form a peroxyl type of radical (k = 6 × 10⁷ dm³ mol⁻¹ s⁻¹). At pH 10.5, where both the hydroxyl groups of CGA are deprotonated, the rate of reaction of · OH radicals with CGA was essentially the same as at pH 5.5, although there was a marked shift in the absorption maximum to approx. 500 nm. The CGA phenoxyl radical formed with more specific one-electron oxidants, viz., Br ₂ ^·− and N ₃ ^· radicals show an absorption maximum at 385 and 500 nm, k ranging from 1–5.5 × 10⁹ dm³ mol⁻¹ s⁻¹. Reactions of other one-electron oxidants, viz., NO ₂ ^· , NO^· and CCl₃OO^· radicals, are also discussed. Repair rates of thymidine, cytidine and guanosine radicals generated pulse radiolytically at pH 9.5 by CGA are in the range of (0.7–3) × 10⁹ dm³ mol⁻¹ s⁻¹.     

杜仲叶中绿原酸的协同增敏荧光光谱法测定

研究了四硼酸钠-阳离子表面活性剂十六烷基三甲基溴化铵(CTMAB)微乳液混合体系对绿原酸的协同荧光增敏作用.结果表明,单独存在的四硼酸钠和CTMAB对绿原酸的荧光强度无显著增敏作用,但四硼酸钠-CTMAB混合体系对绿原酸具有较好的协同荧光强度增敏作用.在优化条件下,绿原酸浓度在0.13～1.32μg·mL<-1>范围内...     

Determination of baicalin, chlorogenic acid and caffeic acid in traditional chinese medicinal preparations by capillary zone electrophoresis

Summary A capillary zone electrophoresis (CZE) method was developed for the simultaneous assay of three bioactive components—baicalin, chlorogenic acid and caffeic acid—in seven traditional Chinese medicinal preparations. The analytes were separated successfully within 3.5 min using 10 mM borate buffer (pH8.6). Regression equations revealed linear relationships (correlation coefficients 0.9942–0.9996) between the peak area and concentration of the three analytes. The relative standard deviations of the migration times and the peak areas of the three constituents were 1.12–2.68% and 1.62–5.73%, respectively. Recovery of the three constituents ranged from 89 to 107%. The extraction efficiencies of different extraction solutions are also discussed. The contents of the three components in seven different Chinese medicinal preparations containing Honeysuckle flower and/orScutellariae radix were determined by the CZE method with satisfactory results.     

Equilibrium and <Superscript>1</Superscript>H NMR Kinetic Study of the Reactions of Dichlorido [S-Methyl-L-Cysteine(N,S)]Platinum(II) Complex with Some Relevant Biomolecules

The formation equilibria of the [Pt(SMC)(H₂O)₂]⁺ complex with some biologically relevant ligands such as L-methionine (L-met) and glutathione (GSH) were studied. The stoichiometry and stability constants of the formed complexes are reported, and the concentration distribution of the various complex species has been evaluated as a function of pH. The reaction between [PtCl₂(SMC)] and guanosine-5′-monophosphate (5′-GMP) was studied by ¹H NMR spectroscopy. The NMR spectra indicated that first step is the hydrolysis of the [PtCl₂(SMC)] complex and second step is the substitution of an aqua ligand, either in the cis or trans position with guanosine-5′-monophosphate in molar ratio 1:1. The values of rate constant showed faster substitution of coordinated H₂O in the trans position to the S donor atom of S-methyl-L-cysteine, whereas the slower reaction was assigned to the displacement of the cis coordinated aqua molecule. This is due to the strong trans labilization effect of coordinated sulfur. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

Fatty-acid composition and secondary metabolites from slightly polar extracts of the aerial part of <Emphasis Type="Italic">Primula macrocalyx</Emphasis>

Flavones 2′,5′-dimethoxyflavone, 3′-methoxy-4′,5′-methylenedioxyflavone, 3′,4′-dimethoxyflavone, 5,6,2′,3′,6′-pentamethoxyflavone, and 5,6,2′,3′,5′,6′-hexamethoxyflavone; salicylates, methyl-4-methoxysalicylate and peonol; and bisbibenzyl polyphenol riccardin C were isolated for the first time from the acetone extract of the aerial part of Primula macrocalyx Bge. The content of free and total fatty acids was determined by GC and GC—MS. Palmitic (16:0), octadecatetraenoic 18:4 (6,9,12,15), linoleic 18:2 (9,12), and α-linolenic 18:3 (9,12,15) were the principal acids from the aerial part of Primula macrocalyx. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 457–460, September-October, 2008.     

Determination of baicalin, chlorogenic acid and forsythin in Chinese medicinal preparation by capillary electrophoresis

Summary The determination of baicalin, chlorogenic acid and forsythin in a traditional Chinese medicinal preparation, Shuanghuanglian oral liquid, has been investigated by micellar electrokinetic capillary electrophoresis using borate buffer, SDS and acetonitrile as background electrolyte, 15 kV applied voltage and UV detection, the three active compounds were completely separated within 15 min. The effect of buffer pH, concentration of borate and SDS are discussed. Regression equations reveal linear relationships between the peak-area of each component and content. In addition, the levels of three active compounds in traditional Chinese medicinal preparation, Shuanghuanglian oral liquid, were easily determined with recoveries of 95.20–105.73%.     

Energy basis of recognition of base pair for platinum-based antitumour drug ZD0473 and cisplatin

Platinum-based antitumour drug ZD0473 was designed to reduce the cisplatin resistance to the tumor cells. In this paper, the mixed method of molecular mechanics and quantum chemistry, HF/lanl2dz// MM/uff and B3LYP/lanl2dz//6-31G*, are used to investigate the differences between four types of GG, 3′AG5′, 3′GA5′, and AA complexes, which are formed from four discrete DNA fragments recognized by ZD0473 and cisplatin. The results show that the binding interaction of both ZD0473 and cisplatin drugs with the GG base pair is much stronger than with other base pairs, namely the recognition capability of such drugs to the GG base pair is more considerable. Moreover, the interaction of four complexes of ZD0473 with DNA fragments is stronger than that of cisplatin with corresponding DNA fragments, which indicates the stronger binding capability of ZD0473 with DNA fragments and high antitumour activity of ZD0473. The main reason for easier forming of 3′GA5′ complex than the 3′AG5′ one is that the drug molecule prefers to bind with a single G base to form a monoligand compound firstly; then the con- figuration transformation from such monoligand compound to the bi-ligand one is limited.     

Determination and pharmacokinetic study of chlorogenic acid in rat dosed with Yin-Huang granules by RP-HPLC

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method was described for the determination of chlorogenic acid (CGA) in rat plasma using protocatechuic acid as internal standard (IS). CGA in plasma was extracted with acetonitrile, which also acted as deproteinization agent. Chromatographic separation was performed on a Kromasil C18 column with methanol-0.2 m acetic acid (pH 3.0, 25:75, v/v) as mobile phase at a flow-rate of 1.0 mL/min with an operating temperature of 30 degrees C and UV detection at 300 nm. The standard curve was found to be linear over the concentration ranges of 0.4-2.5 microg/mL and 2.5-40 microg/mL, and the limit of quantification (LOQ) was 0.4 microg/mL. The analytical precision and accuracy were validated by relative standard deviation (RSD) and relative error, which were in ranges 3.14-10.78% and -2.20-5.00%, respectively. The average recovery of CGA was 87.59%. The method was successfully applied to the pharmacokinetic study of CGA in Yin-Huang granules.     

Sulfonation of 4′-acetyl-, 4′-(<Emphasis Type="Italic">tert</Emphasis>-butyl)-dibenzo-18-crown-6 and (dibenzo-18-crown-6)-4′-sulfonic acid with potassium sulfate in polyphosphoric acid

The sulfonation of monosubstituted derivatives of dibenzo-18-crown-6 with potassium sulfate in polyphosphoric acid has been carried out. Sulfonic acids with various functional groups in the second nucleus of dibenzo-18-crown-6 have been obtained. A qualitative comparison of the reactivity of the substrates gave information on the transfer of the electronic influence of a substituent through the macrocycles. The displacement of electron density in the benzene nuclei of the substrates and the products of sulfonation was assessed from the value of the displacement of the proton signals in the ¹H NMR spectra. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 370–375, March, 2009.     

Investigations on 2,3′-Biquinolyl. 16. The Regioselectivity of Reduction of 1-Alkyl-3-(2-quinolyl)quinolinium and 1,1′-Dialkyl-3,3′-di(2-quinolyl)-1,1′,4,4′-biquinolyl Iodides Using Metallic Zinc,Lithium and Potassium

The reaction of 1-alkyl-3-(2-quinolyl)quinolinium iodides with excess zinc in THF gives a diastereomeric mixture of 1,1′-dialkyl-3,3′-di(2-quinolyl)-1,1′,4,4′-tetrahydro-4,4′-biquinolyls. An excess of lithium in THF gives a mixture of 1′,2′-dihydro-2,3′-biquinolyl and 1′-alkyl-1′, 4′-dihydro-2,3′-biquinolyl with the former predominating. The reduction by lithium in THF of 1,1′-dialkyl-3,3′-di(2-quinolyl)-1,1′,4,4′-tetrahydro-4,4′-biquinolyls leads to analogous products. Reduction of 1-alkyl-3-(2-quinolyl)quinolinium iodides by metallic potassium gives 1-alkyl-1′,4′-dihydro-2,3′-biquinolyls. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1208–1212, August, 2005.     

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.     

Synthesis of a Bifunctional 1,1′-Diphenyl-1,2,3,4-tetrahydroquinoline Derivative: 1,1′-Diphenyl-1,2,3,4,1′,2′,3′,4′-octahydro-6,6′-biquinolinyl-3,3′-diol

Summary. Intramolecular cyclization of N,N′-di(3-chloro-2-hydroxy)propyl-N,N′-diphenylbenzidine occurs to give bis-1,2,3,4-tetrahydroquinoline derivative 1,1′-diphenyl-1,2,3,4,1′,2′,3′,4′-octahydro-6,6′-biquinolinyl-3,3′-diol.     

2-Amino-5,5-bis(hydroxymethyl)-1,3-thiazol-4(5H)-one and its spirodioxane compounds in the Mannich reaction

It was found that the aminomethylation of 2-amino-5,5-bis(hydroxymethyl)-1,3-thiazol-4(5H)-one and its spiro analogs using primary amines is accompanied by cyclization at the amidine fragment of the molecule with annelation of a tetrahydrotriazine ring. When using secondary amines the aminomethylation occurs at the exocyclic nitrogen atom. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1252–1260, August, 2006.     

A novel compound from <Emphasis Type="Italic">Flos carthami</Emphasis> and its bioactivity

A novel compound, 4-{1′-hydroxy-1′-mercapto-1′-[1′′-2′′(N→O)-isoquinolyl]}yl-1-benzoic acid (1), together with six known compounds, 6-hydroxykaempferol-3-O-β-D-glucopyranoside (2), rutin (3), quercetin-3-O-β-D-glucopyranoside (4), kaempferol-3-O-β-D-glucopyranoside (5), cartormin (6), hydroxysafflor yellow A (7), were isolated by chromatography from the n-BuOH fraction of 50% ethanol extraction of Flos carthami. Their structures were elucidated on the basis of spectral analysis and comparison with published data. Among them, compound 1 was shown to possess a weak protective effect against cerebral ischemic damage in rats. Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 339–341, May–June, 2009.     

Investigations on 2,3′-biquinolines. 18. New convenient one-pot synthesis of 1′-alkyl-1′,4′-dihydro-2,3′-biquinolyl-4′-thiones and their conversion into 1′-alkyl-1′,4′-dihydro-2,3′-biquinolyl-4′-ones

A method has been developed for the one pot synthesis of 1′-alkyl-1′,4′-dihydro-2.3′-biquinolyl-4′-thiones based on the reduction of 1-alkyl-3-(2-quinolyl)quinolinium halides with sodium borohydride and subsequent thiolation. 1′-Alkyl-1′,4′-dihydro-2,3′-biquinolyl-4′-ones were obtained in close to quantitative yield by the oxidation of 1′-alkyl-1′, 4′-dihydro-2,3′-biquinolyl-4′-thiones. For Part 17 see [1]. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 67–70, January, 2006.     

Flavones from Callus Tissue of <Emphasis Type="Italic">Iris ensata</Emphasis>

Flavonoids uncharacteristic of intact plants were isolated from callus tissue of Iris ensata and were identified as 5-hydroxy-4′-methoxyflavone, 5-hydroxy-3′-methoxyflavone, and 5-hydroxy-2′-methoxyflavone using PMR and mass spectrometry. It was proposed that the lack of growth of callus tissue after changing cultivation conditions was related to the inhibiting effect of these flavones on cell proliferation. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 440–442, September–October, 2005.