Quantitative analysis of multiple urinary biomarkers of carcinoid tumors through gold-nanoparticle-assisted laser desorption/ionization time-of-flight mass spectrometry

A simple technique for quantitative analysis of four urinary biomarkers, tryptophan (TRP), 5-hydroxytryptophan (5-HTP), 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) of carcinoid tumors is developed using gold nanoparticles as the assisted matrix in surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI–TOF MS). The optimal SALDI conditions for the efficient ionization of those biomarkers are systematically explored by the adjustments of the concentrations of gold nanoparticles and internal standards. The mass spectra with strong signals and minimal background noise are obtained using 1-naphthaleneacetamide (NAD) as the internal standard. The calibration curves of the biomarker concentrations are determined using SALDI–TOF MS and the high linearity is obtained in all samples. For future clinical testing, multiplexed detection of those biomarkers in the urine samples of healthy males is performed. The successful quantitative detections of TRP, 5-HTP, 5-HT and 5-HIAA indicate that our technique provided great potentials to be developed a simple and rapid platform for the tumor biomarker detections.     

Measurement and correlation of solubilities of apigenin and apigenin 7-O-rhamnosylglucoside in seven solvents at different temperatures

The solubilities of apigenin and apigenin 7-O-rhamnosylglucoside in water, methanol, ethanol, 1-propanol, 1-butanol, acetone, and ethyl acetate from T = (288.2 to 328.2) K were measured. The solubilities of apigenin and apigenin 7-O-rhamnosylglucoside in selected solvents increase with increasing temperature, respectively. The experimental solubility data were correlated by a simplified thermodynamic equation and a three-parameter empirical equation.     

Facile synthesis of a 4-anilinoquinazoline dimer by Suzuki cross-coupling reaction

A novel 4-anilinoquinazoline dimer linked by a carbon-carbon bond in the C-7 position was synthesized via a one step Suzuki cross-coupling reaction. All structures of new compounds were characterized by ¹H NMR, ¹³C NMR, and HRMS. The inhibition rate of the synthetic 4-anilinoquinazoline dimer 8 against epidermal growth factor receptor-tyrosine kinase enzymes (EGFR) in vitro was 44.4% at the concentration of 5.5 μmol/L.     

Microwave-assisted synthesis of some novel fluorinated pyrazolo[3,4-d]pyrimidine derivatives containing 1,3,4-thiadiazole as potential antitumor agents

A facile microwave-assisted procedure for synthesis of novel fluorinated pyrazolo[3, 4-d]pyrimidine derivatives containing 1, 3, 4-thiadiazole is described. This protocol presented such advantages as short reaction time, high yields, simple purification and environmentally benign procedures. Their antitumor activities were evaluated against HL-60 by an MTT assay. The preliminary results indicated that some title compounds exhibit more potent antitumor inhibitory activity than doxorubicin (DOX).     

Chain extension of adipic acid and (or) succinic acid/butanediol polyesters with 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and adipoylbiscaprolactamate combined chain extenders

This paper provided an easy and flexible method to synthesize high molecular weight polyesters by polycondensation and chain extension. Low molecular weight polybutylene adipate, polybutylene succinate, and poly(butylene succinate‐co‐butylene adipate) (PBSA) were synthesized through melt condensation polymerization from adipic acid and/or succinic acid with butanediol. The prepolyesters obtained had different amount of ? COOH and ? OH terminal groups. Chain extension of them was carried out at 180–240°C using 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and adipoyl biscaprolactamate as combined chain extenders. The influencing factors of the chain extension were studied. At the optimal conditions, chain‐extended polybutylene adipate with M_n up to 39,100, polybutylene succinate with intrinsic viscosity of 0.99 dl/g, and PBSA with intrinsic viscosity from 0.73 to 0.81 dl/g were synthesized. The chain‐extended polyesters were characterized by IR spectrum, ¹H NMR spectrum, differential scanning calorimetry, thermogravimetric analysis (TGA), wide angle X‐ray scattering, and tensile test. The thermal analysis showed that chain extension often led to slight decrease of the regularity, the crystallinity, and the melting point. This deterioration of the properties is not harmful enough to impair their thermal properties and obstruct them from being used as biodegradable thermoplastics. The TGA showed that the chain‐extended polyesters were stable with initial decomposition temperature over 354.7°C. The tensile strength of the chain extended PBS and PBSAs with butylene adipate units less than 20 mol% was in the range of 18.95–31.22 MPa. Copyright © 2010 John Wiley & Sons, Ltd.     

Synchronous high-performance liquid chromatography with a photodiode array detector and mass spectrometry for the determination of citrinin, monascin, ankaflavin, and the lactone and acid forms of monacolin K in red mold rice

The Monascus fermentation product red mold rice (RMR) has been found to contain the cholesterol-lowering agent monacolin K (MK) in both its lactone (MKL) and acid (MKA) forms and the mycotoxin citrinin (CT). The yellow pigments in RMR, namely, monascin (MS) and ankaflavin (AK), have been reported to exhibit antimetastatic and antiangiogenic activities. Currently, MK and these yellow pigments are usually detected in RMR by different analytical methods that are inconvenient, expensive, and time-consuming. The goal of this study was to establish a rapid, synchronous analytical method for determination of the MKA, MKL, MS, AK, and CT levels in RMR. MKA, MKL, MS, AK, and CT were extracted by the same extraction method, then separated by RP-HPLC with a C18 column. The effluent from the column was passed through a photodiode array detector and then introduced directly into a fluorescence detector. The results showed that high recovery rates of MKA, MKL, MS, AK, and CT are possible if RMR powder is extracted with 75% ethanol (10 mL) at 80 degrees C for 30 min. With regard to the optimal conditions of the HPLC, the peaks of MKA, MKL, MS, AK, and CT can be clearly separated from any noise peaks by isocratic elution with a mobile phase comprising 0.05% trifluoroacetic acid in acetonitrile-water (62.5 + 37.5, v/v).     

Bis(diamino-diamido)-tetrathiafulvalene, a redox active sensor for proton, anions, and cations

A bis(diamino-diamido) tetrathiafulvalene (TTF) derivative H(4)L(2) has been designed and synthesized. Experiments of pH titration reveal that integrating the redox active TTF unit with the diamino-diamido moiety adds new properties to the traditional ligand. Oxidation of the TTF moiety increases the acidity of the amido group, and the coordination of metal ions is also sensitive to the oxidation state of the ligand. This compound is capable of acting as a leaving or accepting ligand for proton and metal ions. The electrochemistry of the protonated TTF derivative of H(4)L(2) was studied in the presence of a series of oxo anions and metal cations. The results indicate that the redox potentials selectively respond to HC(2)O(4)(-) and SO(4)(2-) anions, and Ni(II) and Cu(II) cations. Solid-state structures of a cation-anion salt H(8)L(2)·2SO(4)·8H(2)O and a nickel coordination compound [Ni(2)L(2)]·2DMF have been characterized by means of X-ray crystallography which are helpful in understanding the inter-ion interactions.     

Neutral and cationic chiral NCN pincer nickel(II) complexes with 1,3-bis(2'-imidazolinyl)benzenes: synthesis and characterization

Chiral 1,3-bis(2'-imidazolinyl)benzenes 1a-e easily undergo direct nickelation at the C2 position of the central benzene ring via the C-H bond activation in the reaction with anhydrous NiCl(2) giving neutral NCN pincer nickel(II) complexes 2a-e in 40-87% yields. Treatment of the nickel pincers 2a or 2c with AgBF(4) in CH(3)CN-CH(2)Cl(2) afforded the cationic nickel pincers 3a or 3c in good yields. All the complexes were characterized by elemental analysis, (1)H, (13)C NMR, and IR spectra. Molecular structures of the neutral complexes 2a, 2b and 2c as well as the cationic complex 3c have been determined by X-ray single-crystal diffraction. The cationic nickel pincers 3 are found to be effective catalysts for the Michael addition of ethyl 2-cyanopropionate to methyl vinyl ketone in the presence of i-Pr(2)NEt base with a catalyst loading of 5 mol% even at -78 °C, producing the adduct in >99% yield after 24 h albeit with no ee.     

The cyclicity and period function of a class of quadratic reversible Lotka-Volterra system of genus one

In this paper, we investigate a class of quadratic reversible Lotka-Volterra system of genus one with b=3/5. It is proved that the cyclicity of the period annulus under quadratic perturbations is equal to two. Moreover, we prove that the period function of its period trajectories is monotone increasing.