tempo and 1-1-diphenyl-2-picrylhydrazyl

Piperine, as the most abundant alkaloid in pepper, gained a lot of attention for possible antioxidant and therapeutic properties. Electrochemical techniques were applied to widely evaluate the redox behavior of piperine by comparison to that of well-known antioxidants: ascorbic acid, protocatechuic acid, syringic acid, tyrosine and capsaicin used as controls. Also, electrochemistry was involved in an innovative way to investigate the potential antioxidant properties of piperine combined with different in vitro peroxidation and reducing assays: (i) 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging; (ii) 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) scavenging; (iii) ferric ions (Fe

Topics: Alkaloids; Antioxidants; Ascorbic Acid; Benzodioxoles; Biphenyl Compounds; Cyclic N-Oxides; Electrochemical Techniques; Free Radical Scavengers; Free Radicals; Hydrogen Peroxide; Iron; Oxidation-Reduction; Picrates; Piperidines; Polyunsaturated Alkamides

A xanthouronic acid sodium salt called xanthouronan was produced from xanthan by regioselective oxidation with NaOCl/NaBr using 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) as catalyst. The efficiency of the one pot TEMPO-mediated oxidation was confirmed by HPAEC-PAD, (13)C NMR, and FT-IR. The oxidation degree was close to 98% and the mass yield of this new polyglucuronic acid was higher than 90% (w/w). The macromolecular characterization of xanthouronan using SEC-MALLS showed a molecular size reduced by a third due to the oxidation treatment and the degree of polymerization (DP) of the xanthouronan form was about 665. The evaluation of the enzymatic degradation of this C-6 carboxylated xanthan by various polysaccharide hydrolases and one polysaccharide lyase showed its high resistant to biodegradation. The antioxidant activity of xanthouronan was also tested by using the 2,2'-diphenyl-1-picrylhydrazyle (DPPH) and hydroxyl radical procedures. At 1 g/L, xanthouronan presented 75% of the ascorbic acid antioxidant activity.

Topics: Antioxidants; Biphenyl Compounds; Bromides; Catalysis; Cyclic N-Oxides; Oxidation-Reduction; Picrates; Polysaccharides; Polysaccharides, Bacterial; Sodium Compounds; Sodium Hydroxide; Sodium Hypochlorite; Uronic Acids

An oxygen-insertion reaction that transforms an o-quinone and a conjugated α-diketone substrate into an anhydride product or derivative under catalytic hydrogenation conditions is reported. The experiments and computations indicate that the oxygen insertion proceeds via a radical mechanism mediated by an acetoxyl radical.

Topics: Biphenyl Compounds; Catalysis; Combinatorial Chemistry Techniques; Cyclic N-Oxides; Heterocyclic Compounds; Hydrogenation; Molecular Structure; Oxygen; Picrates; Quinones

Replacement of protons by deuterons in the glassing solvents led to 2-3-fold improvement of the (13)C dynamic nuclear polarization (DNP) solid-state NMR signal for samples doped with large electron spin resonance (ESR) linewidth free radicals galvinoxyl, DPPH, and 4-oxo-TEMPO. Meanwhile, the reverse effect is observed for (13)C DNP using small ESR linewidth free radicals BDPA and trityl OX063.

Topics: Allyl Compounds; Benzhydryl Compounds; Biphenyl Compounds; Cyclic N-Oxides; Deuterium; Electron Spin Resonance Spectroscopy; Magnetic Resonance Spectroscopy; Picrates

TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated 6-carboxy β-chitin derivatives (T-chitin) with different carboxylate content were successfully synthesized by controlling the addition level of NaClO as the primary oxidant. The structural and biochemical properties of the derivatives were investigated. The carboxylate contents of the derivatives calculated by electrical conductivity titration were 1.33, 1.68, 1.80, and 2.08 mmol/g, respectively. The yield of T-chitin with carboxylate content of 2.08 mmol/g reached 74.55%. T-chitin exhibited stronger bile acid binding capacities than that of β-chitin. The scavenging ability of T-chitin against hydroxyl radicals improved with increasing concentration, and EC(50) values were below 1.2 mg/mL. All T-chitin exhibited a strong ferrous ion chelating effect. At 8 mg/mL, the chelating effects of T-chitin with carboxylate content of 0.81 mmol/g reached 80.15%. These results showed that T-chitin had good bile acid binding capacity and antioxidant activities and it may be a potential antioxidant in vitro.

Topics: Animal Shells; Animals; Bile Acids and Salts; Biphenyl Compounds; Bromides; Carboxylic Acids; Chitin; Cyclic N-Oxides; Decapodiformes; Free Radical Scavengers; Hydroxyl Radical; Iron Chelating Agents; Oxidation-Reduction; Picrates; Sodium Compounds; Sodium Hypochlorite

The antioxidant effects of chlorophyllin (CHL), a water-soluble analog of the green plant pigment chlorophyll, on different reactive oxygen species (ROS) were investigated by electron spin resonance (ESR) spectroscopy. As a standard, we have used the ability of CHL to scavenge the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. CHL inhibits the formation of 5,5-dimethyl-1-pyrroline-N-oxide adduct with hydroxyl radical (DMPO-.OH adduct) generated by gamma-radiation in a dose-dependent manner. At a concentration of 1 mM, CHL caused more than 90% inhibition of ESR signal intensity of this adduct. However, the results obtained with the Fenton reaction were different. We also found evidence for the inhibition of 1O2-dependent formation of the 2,2,6,6-tetramethyl-piperidine oxide (TEMPO) radical during photosensitization of methylene blue with visible light. CHL was also able to inhibit hydrogen peroxide induced oxidation of phenol red. The rate constant of the reaction of CHL with H2O2 was found to be 2.7 x 10(6) M-1 s-1. In conclusion, CHL has potent antioxidant ability involving scavenging of various physiologically important ROS.

Topics: Bepridil; Biphenyl Compounds; Chlorophyllides; Cyclic N-Oxides; Electron Spin Resonance Spectroscopy; Free Radical Scavengers; Free Radicals; Hydrogen Peroxide; In Vitro Techniques; Picrates; Reactive Oxygen Species; Spin Labels