scholarly journals Pseudoperoxidase activity of 5-lipoxygenase stimulated by potent benzofuranol and N-hydroxyurea inhibitors of the lipoxygenase reaction

1991 ◽  
Vol 274 (1) ◽  
pp. 287-292 ◽  
Author(s):  
D Riendeau ◽  
J P Falgueyret ◽  
J Guay ◽  
N Ueda ◽  
S Yamamoto
Keyword(s):  
Nordihydroguaiaretic Acid ◽  
Leukotriene B4 ◽  
Reducing Agents ◽  
Lipid Hydroperoxides ◽  
Reverse Phase ◽  
Structural Analogues ◽  
The Stability ◽  
Hydroperoxyoctadecadienoic Acid ◽  
Derivatives Of ◽  
Stimulation Of

The purified 5-lipoxygenase from porcine leukocytes was found to catalyse the degradation of lipid hydroperoxides in the presence of potent inhibitors of the lipoxygenase reaction. Derivatives of diphenyl-N-hydroxyureas, 4-hydroxybenzofurans and 5-hydroxydihydrobenzofurans all stimulated the 5-lipoxygenase-mediated destruction of 13-hydroperoxyoctadecadienoic acid (13-HPOD). The reaction was dependent on inhibitor and hydroperoxide concentrations (1-10 microM) and could not be detected using heat-inactivated enzyme, when ATP and Ca2+ were omitted or when the hydroperoxide was replaced by the corresponding alcohol. The stability of the inhibitors during this pseudoperoxidase reaction was investigated by measuring the recoveries of 5-hydroxy-2-phenethyl-6-(3-phenoxypropyl)-2,3-dihydrobenzofuran and N-(4-chlorophenyl)-N-hydroxy-N'-(3-chlorophenyl)urea from the reaction mixtures using reverse-phase h.p.l.c. By using an equimolar concentration of 13-HPOD and inhibitor (10 microM) and under conditions where 50% of the 13-HPOD was consumed, the concentration of the benzofuranol decreased by 30%, whereas the N-hydroxyurea derivative could be completely recovered from the reaction mixture. A stimulation of the pseudoperoxidase reaction could be detected only with very effective inhibitors of leukotriene B4 biosynthesis by human leucocytes [IC50 (concn. causing 50% inhibition) less than 100 nM], but not with closely related structural analogues of lower potency or other inhibitors such as nordihydroguaiaretic acid, quercetin or the hydroxamate A-64077. These results demonstrate that 5-lipoxygenase possesses a pseudoperoxidase activity and indicate that potent inhibitors in both N-hydroxyurea and benzofuranol series can function as reducing agents for the enzyme.

Methods for the Concentration of Bovine Ac-Globulin (Factor V)

1961 ◽  
Vol 06 (03) ◽  
pp. 435-444 ◽  
Author(s):  
Ricardo H. Landaburu ◽  
Walter H. Seegers
Keyword(s):  
Room Temperature ◽  
Barium Carbonate ◽  
Deae Cellulose ◽  
Reducing Agents ◽  
Factor V ◽  
Isoelectric Precipitation ◽  
Stabilizing Agent ◽  
Bovine Plasma ◽  
The Stability

SummaryAn attempt was made to obtain Ac-globulin from bovine plasma. The concentrates contain mostly protein, and phosphorus is also present. The stability characteristics vary from one preparation to another, but in general there was no loss before 1 month in a deep freeze or before 1 week in an icebox, or before 5 hours at room temperature. Reducing agents destroy the activity rapidly. S-acetylmercaptosuccinic anhydride is an effective stabilizing agent. Greatest stability was at pH 6.0.In the purification bovine plasma is adsorbed with barium carbonate and diluted 6-fold with water. Protein is removed at pH 6.0 and the Ac-globulin is precipitated at pH 5.0. Rivanol and alcohol fractionation is followed by chromatography on Amberlite IRC-50 or DEAE-cellulose. The final product is obtained by isoelectric precipitation.

Binding of calcium and lead ions to carboxystarch prepared by action of nitrogen dioxide on native starch and its 2,3-dialdehyde derivatives

1986 ◽  
Vol 51 (6) ◽  
pp. 1340-1351 ◽  
Author(s):  
Rudolf Kohn ◽  
Karol Tihlárik
Keyword(s):  
Nitrogen Dioxide ◽  
Alkaline Medium ◽  
Binding Capacity ◽  
Lead Ions ◽  
Carbonyl Groups ◽  
Weakly Alkaline ◽  
Exchange Cations ◽  
Counter Ions ◽  
The Stability ◽  
Derivatives Of

The binding of calcium and lead ions to carboxy derivatives of starch prepared by allowing nitrogen dioxide to act on native maize starch (procedure A) and on starch 2,3-dialdehyde derivatives of degrees of oxidation DO(d.a.) ≥ 0.94 (procedure B) was studied. The carboxy group content of the samples in the H+ form was 4.6 - 12.1 mmol g-1. The effect of alkaline medium on the stability of the carboxy derivatives and on their ability to bind and exchange cations was examined. The Ca2+ → 2K+ exchange was evaluated in terms of the decrease in the electrostatic free enthalpy Δ(Gel/N)KCa, determined by alkalimetric potentiometric titrations, and the binding of Pb2+ ions was evaluated in terms of the activity of the Pb2+ counter-ions determined in suspensions of Pb salts of the carboxy derivatives by means of an ion specific electrode. The IR and CD spectra revealed that the carboxystarch preparations obtained by procedure A contained, in addition to free carboxy groups, a considerable amount of carbonyl groups. During the conversion of the latter groups to the former, even in a weakly alkaline medium, the carboxy derivatives undergo an appreciable degradation and lose, to a great extent, their ability to bind and exchange cations. Procedure B, on the other hand, leads to highly selective starch and amylose carboxy derivatives, exhibiting a small amount of carbonyl groups and featuring a relative stability towards alkaline medium; their binding capacity is as high as 12 milliequivalents of cations per g of sample.

scholarly journals Antioxidant Network Based on Sulfonated Polyhydroxyalkanoate and Tannic Acid Derivative

2021 ◽  
Vol 8 (1) ◽  
pp. 9
Author(s):  
Laura Brelle ◽  
Estelle Renard ◽  
Valerie Langlois
Keyword(s):  
Gallic Acid ◽  
Tannic Acid ◽  
Water Soluble ◽  
Gel Formation ◽  
Ene Reaction ◽  
Inorganic Cations ◽  
Medium Chain Length ◽  
Physically Crosslinked ◽  
The Stability ◽  
Derivatives Of

A novel generation of gels based on medium chain length poly(3-hydroxyalkanoate)s, mcl-PHAs, were developed by using ionic interactions. First, water soluble mcl-PHAs containing sulfonate groups were obtained by thiol-ene reaction in the presence of sodium-3-mercapto-1-ethanesulfonate. Anionic PHAs were physically crosslinked by divalent inorganic cations Ca2+, Ba2+, Mg2+ or by ammonium derivatives of gallic acid GA-N(CH3)3+ or tannic acid TA-N(CH3)3+. The ammonium derivatives were designed through the chemical modification of gallic acid GA or tannic acid TA with glycidyl trimethyl ammonium chloride (GTMA). The results clearly demonstrated that the formation of the networks depends on the nature of the cations. A low viscoelastic network having an elastic around 40 Pa is formed in the presence of Ca2+. Although the gel formation is not possible in the presence of GA-N(CH3)3+, the mechanical properties increased in the presence of TA-N(CH3)3+ with an elastic modulus G’ around 4200 Pa. The PHOSO3−/TA-N(CH3)3+ gels having antioxidant activity, due to the presence of tannic acid, remained stable for at least 5 months. Thus, the stability of these novel networks based on PHA encourage their use in the development of active biomaterials.

scholarly journals Validation of developed method by RP-HPLC for simultaneous estimation of famotidine and ibuprofen in human plasma and studying the stability of the drugs in plasma

2018 ◽  
Vol 12 (1) ◽  
pp. 34-48
Author(s):  
K. S Ashutosh ◽  
D. Manidipa ◽  
R. J. V. L. N. Seshagiri ◽  
S. D. Gowri
Keyword(s):  
Human Plasma ◽  
Mobile Phase ◽  
Simultaneous Estimation ◽  
Hplc Separation ◽  
Reverse Phase ◽  
Rp Hplc ◽  
The Stability ◽  
Sodium Dihydrogen ◽  
Isocratic Mode

The RP-HPLC separation was carried out by reverse phase chromatography on a Symmetry C18 (4.6 x 150 mm, 3.5 μm, make: XTerra) with a mobile phase composed of sodium dihydrogen ortho phosphate [pH 2.5] and acetonitrile in the ratio of 30:70 v/v in an isocratic mode at a flow rate of 1.2 mL/min. The run time was maintained for 8.0 min. The detection was monitored at 236 nm. The accuracy was calculated in human plasma and the % recovery was found 99.80 - 99.85 for famotidine and 99.56 -99.85.5 for ibuprofen and reproducibility was found to be satisfactory. The calibration curve for famotidine in human plasma was linear over 3.32 to 6.65 μg/mL and 100- 200 μg/mL for ibuprofen in human plasma respectively. The inter-day and intra-day precision in human plasma was found within limits. The proposed method has adequate sensitivity, reproducibility, and specificity for the determination of famotidine and ibuprofen in plasma. The LLOQ obtained by the proposed method in human plasma were 1.24 and 5.0 μg/mL for famotidine and ibuprofen respectively. The proposed method is simple, fast, accurate, and precise for the quantification of famotidine and ibuprofen in plasma as per the ICH guidelines.Kathmandu University Journal of Science, Engineering and TechnologyVol. 12, No. I, June, 2016, Page: 34-48

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