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A new sesquiterpenoid hydroquinone from the marine sponge Dysidea arenaria.
Molecules. 2008; 13(6): 1275-81
Qiu Y, Wang XM
Detailed chemical investigation of the South China sponge Dysidea arenaria resulted in the isolation of a new sesquiterpenoid hydroquinone, 19-hydroxypolyfibrospongol B (1), along with five known compounds: polyfibrospongol B (2), isosemnonorthoquinone (3), ilimaquinone (4), smenospongine (5) and smenotronic acid (6). The structures were determined by extensive spectroscopic analysis. The in vitro anti- HIV activity on HIV-1 RT was evaluated. Compounds 3 -6 displayed moderate inhibitory activity, with IC(50)values of 239.7, 16.4, 176.1, and 130.4 microM, respectively, while 1 and 2 were found to be inactive against the same biological target.
Talanta. 2008 Jul 15; 76(2): 424-31
Preechaworapun A, Dai Z, Xiang Y, Chailapakul O, Wang J
In this paper, we have critically evaluated the electrochemical behavior of the products of seven substrates of the enzyme label, alkaline phosphate, commonly used in electrochemical immunosensors. These products (and the corresponding substrates) include indigo carmine (3-indoyl phosphate), hydroquinone (hydroquinone diphosphate), 4-nitrophenol (4-nitrophenol phosphate), 4-aminophenol (p-aminophenyl phosphate), 1-naphthol (1-naphthyl phosphate), phenol (phenyl phosphate), and L-ascorbic acid (2-phospho-L-ascorbic acid). Cyclic voltammetry and amperometry of these products were carried out at glassy carbon (GC), screen-printed carbon (SPC) and gold (Au) electrodes, respectively. Among the products, L-ascorbic acid showed the most sensitive (24.8 microA cm(-2), 12.0 microA cm(-2), and 48.0 microA cm(-2) of 100 microM ascorbic acid at GC, SPC, and Au electrodes, respectively) and well-defined amperometric response at all electrodes used, making 2-phospho-l-ascorbic acid the best substrate in electrochemical detection involving an alkaline phosphatase (ALP) enzyme label. The 2-phospho-L-ascorbic acid is also commercially available and inexpensive. Therefore, it was the best choice for electrochemical detection using ALP as label. Using mouse IgG as a model, an ALP enzyme-amplified sandwich-type amperometric immunosensor was constructed. The immunosensor was designed by electropolymerization of o-aminobenzoic acid (o-ABA) conductive polymer on the surface of GC, SPC, and Au electrodes. The anti-mouse IgG was subsequently attached on the electrode surface through covalent bonding between IgG antibody and the carboxyl groups from poly(o-ABA). Using 2-phospho-L-ascorbic acid as a substrate, the poly(o-ABA)/Au immunosensor produced the best signal (about 297 times of current density response ratio between 1000 ng mL(-1) and 0 ng mL(-1) of mouse IgG), demonstrating that amperometric immunosensors based on a conducting polymer electrode system were sensitive to concentrations of the mouse IgG down to 1 ng mL(-1), with a linear range of 3-200 ng mL(-1) (S.D.
Immunonanogold-catalytic resonance scattering spectral assay of trace human chorionic gonadotrophin.
Talanta. 2008 Jun 15; 75(5): 1214-20
Liang A, Zou M, Jiang Z
Gold nanoparticles in diameter of 10 nm were used to label rabbit anti-human chorionic gonadotrophin (RhCG) antiserum to obtain a resonance scattering spectral probe (AuRhCG) for human chorionic gonadotrophin (hCG). The immunoreaction between AuRhCG and hCG take place to form hCG-AuRhCG immunocomplex in pH 5.0 citric acid-Na(2)HPO(4) buffer solution. The immunocomplex solutions were centrifuged to obtain the supernatant solution. The AuRhCG in the supernatant solution exhibited strong catalytic effect on the particle reaction between Ag(+) and hydroquinone to produce gold-silver composite particles in pH 3.4 citric acid-trisodium citrate buffer solution. There is a stronger resonance scattering (RS) peak at 423 nm for the particles. With the addition of hCG, the AuRhCG in the supernatant solution decreased, and the RS intensity at 423 nm decreased. The decreased RS intensity DeltaI(423 nm) was proportional to the concentration of hCG in the range of 2.5-208.3 mIU/mL with a detection limit of 0.83 mIU/mL. This method has been applied to the determination of hCG in urine samples, with satisfactory results.
Bioelectrochemistry. 2008 May 12;
Somer G, Doğan M
Two methods for the determination of vitamin K(3) have been developed. Vitamin K(3) in its oxidized form is determined by direct and indirect methods. Its standard solution was prepared by the indirect method using Ti(III) as reducing agent. For this purpose vitamin K(3) (menadion) in a clinical injection solution, which is in its hydroquinone form in the presence of sulfite, is oxidized with oxygen. In 0.2 M HAc and 0.02 M HCl electrolyte vitamin K(3) and Ti(IV) have reduction peaks at -0.58 V at -0.82 V respectively. The reaction between Ti(III) and vitamin takes place quantitatively in a medium of 0.2 M HAc and 0.002 M HCl. After the reduction, the reaction product Ti(IV) is followed from its polarographic peak at about -0.82 V. The most important result in this work is that, with this method vitamin K(3) can be standardized and after standardization this solution can be used for the direct determination in routine analysis with a very simple and fast method, using only the peak at -0.71 V in 0.2 M HAc medium. Both direct and indirect methods have been used for the determination of Vitamin K(3) in a clinical injection solution. The limit of quantification (LOQ) was 1.5x10(-6) M and in both methods the detection limit found was 7x10(-7) M.
Hydrogen Peroxide Biosensor with a Supramolecular Layer-by-Layer Design.
Langmuir. 2008 Jun 27;
Camacho C, Matías JC, Cao R, Matos M, Chico B, Hernández J, Longo MA, Sanromán MA, Villalonga R
A new sensor design is reported for the construction of an amperometric enzyme biosensor toward H 2O 2. It was based in the supramolecular immobilization of alternating layers of horseradish peroxidase (either modified with 1-adamantane or beta-cyclodextrin-branched carboxymethylcellulose residues) on Au electrodes coated with polythiolated beta-cyclodextrin polymer. The analytical response of the electrodes, using 1 mM hydroquinone as an electrochemical mediator, increases when the number of enzyme layers increases. The biosensor having three enzyme layers showed a sensitivity of 720 muA/M cm (2) and a detection limit of 2 muM and retained 96% of its initial activity after 30 days of storage. The host-guest supramolecular nature of the immobilization method was confirmed by cyclic voltammetry.
Appl Biochem Biotechnol. 1998 Feb; 69(2): 127-36
Casas DA, Pitta-Alvarez SI, Giulietti AM
Hairy roots ofBrugmansia candida were used to bioconvert hydroquinone into arbutin. The highest bioconversion, with the lowest damage to the cells, was attained when concentrations of 20-40 mg/L hydroquinone were used. Sugars (sucrose, glucose, mannitol, and sorbitol) at concentrations of 30-120 g/L enhanced bioconversion, and, of these, sucrose was the most effective. Two different free-radical scavengers were also tested: sodium benzoate and gallic acid. The first one diminished biotransformation efficiency; gallic acid did not affect biotransformation at all. Preliminary permeabilization treatments tested failed to liberate arbutin into the medium, and provoked a total loss in cell viability.
Tetrahedron Lett. 2002 May 27; 58(22): 4559-4565
Lindsey CC, Gómez-Díaz C, Villalba JM, Pettus TR
F11334A(1), F11334A(2), F11334A(3), and their corresponding resorcinol analogs were synthesized along with F11334B(1), and F11263. In the course of these synthetic studies, several conditions for manipulating (2,3-propanediol) and (2,3-epoxypropyl) o-substituted phenols were developed as well as a variety of conditions for cleavage of aryl O-t-butyl carbonates. From enzyme assays it appears that the hydroquinone nucleus is the essential structural necessary for N-SMase inhibition. Furthermore, it appears that this family of compounds is comprised of irreversible inhibitors.
Nonlinear Phenomena in Light-Mediated Bromate-Hydroquinone-Benzoquinone Reactions.
J Phys Chem A. 2008 Jun 19;
Li N, Wang J
This study presents an experimental investigation of nonlinear dynamics in the photomediated bromate-1,4-benzoquinone-1,4-hydroquinone reaction, in which the copresence of hydroquinone and benzoquinone results in chemical oscillations taking place shortly after mixing all reagents together, which is in great contrast to the case of a few hours of induction time seen in the bromate-hydroquinone or bromate-benzoquinone photochemical oscillators. It is essential to keep the acid concentration low in order to achieve these oscillations. Measurements with mass spectrometry and UV/vis spectroscopy confirm the formation of hydroquinone-benzoquinone complexes. The results suggest that interactions of hydroquinone and benzoquinone can play a significant role in the kinetics of related chemical systems.
A New Functional Bis(m-phenylene)-32-crown-10-Based Cryptand Host for Paraquats.
J Org Chem. 2008 Jun 13;
Pederson AM, Vetor RC, Rouser MA, Huang F, Slebodnick C, Schoonover DV, Gibson HW
The pseudorotaxane complex of the new hydroxymethyl cryptand 3 with N, N'-dimethyl-4,4'-bipyridinium bis(hexafluorophosphate), PQ(PF 6) 2, has an association constant of 2.0(+/-0.3) x 10 (4) M (-1). In the crystal structure of 3.PQ(PF 6) 2 one of the bonding elements appears to be an aromatic edge-to-face interaction of a paraquat beta-proton with the hydroquinone moiety; this is the first time this interaction has been reported between a cryptand and paraquat.
Chem Res Toxicol. 2008 Jun 13;
Song Y, Wagner BA, Lehmler HJ, Buettner GR
Polychlorinated biphenyls (PCBs) can be oxygenated to form very reactive hydroquinone and quinone products. A guiding hypothesis in the PCB research community is that some of the detrimental health effects of some PCBs are a consequence of these oxygenated forms undergoing one-electron oxidation or reduction, generating semiquinone radicals (SQ (*-)). These radicals can enter into a futile redox cycle resulting in the formation of reactive oxygen species, that is, superoxide and hydrogen peroxide. Here, we examine some of the properties and chemistry of these semiquinone free radicals. Using electron paramagnetic resonance (EPR) to detect SQ (*-) formation, we observed that (i) xanthine oxidase can reduce quinone PCBs to the corresponding SQ (*-); (ii) the heme-containing peroxidases (horseradish and lactoperoxidase) can oxidize hydroquinone PCBs to the corresponding SQ (*-); (iii) tyrosinase acting on PCB ortho-hydroquinones leads to the formation of SQ (*-); (iv) mixtures of PCB quinone and hydroquinone form SQ (*-) via a comproportionation reaction; (v) SQ (*-) are formed when hydroquinone-PCBs undergo autoxidation in high pH buffer ( approximately >pH 8); and, surprisingly, (vi) quinone-PCBs in high pH buffer can also form SQ (*-); (vii) these observations along with EPR suggest that hydroxide anion can add to the quinone ring; (viii) H 2O 2 in basic solution reacts rapidly with PCB-quinones; and (ix) at near-neutral pH SOD can catalyze the oxidization of PCB-hydroquinone to quinone, yielding H 2O 2. However, using 5,5-dimethylpyrroline-1-oxide (DMPO) as a spin-trapping agent, we did not trap superoxide, indicating that generation of superoxide from SQ (*-) is not kinetically favorable. These observations demonstrate multiple routes for the formation of SQ (*-) from PCB-quinones and hydroquinones. Our data also point to futile redox cycling as being one mechanism by which oxygenated PCBs can lead to the formation of reactive oxygen species, but this is most efficient in the presence of SOD.