Water-soluble Initiator Research Articles

Preparation and characterization of magnetic nanoparticles embedded in microgels

This article describes the magnetically responsive microgel that consists of a small iron oxide magnetic nanoparticles (∼15 nm in diameter) embedded in a biocompatible microgel varying from ∼65 to ∼110 nm in diameter. These systems show great promise as active component of microscale and nanoscle devices and are expected to have wide applicability in various biomedical applications. Polymeric microgels have been prepared by emulsion free copolymerization of thermoresponsive N-isopropylacrylamide and acrylic acid with a water-soluble persulfate initiator. The obtained microgel magnetic composite particles possess a lower critical solution temperature (LCST) in water solutions, with a rapid decrease of the particle size being observed at elevated temperatures. The morphology and elemental composition of the composites were characterized by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy (FTIR).

Particle Nucleation Loci in Styrene-Butyl Acrylate Miniemulsion Copolymerization

Miniemulsion polymerizations of styrene and butyl acrylate in the presence of sodium dodecyl sulfate (SDS) as the surfactant and stearyl methacrylate (SMA) as reactive cosurfactant were carried out by using water-soluble (potassium persulfate) and oil-soluble (2,2-azobisisobutyronitrile) (AIBN) initiators respectively. Effects of the two initiators on the particle nucleation mechanisms are investigated. By comparison with the mean diameter of monomer droplets and polymer particles, it is shown that both homogeneous nucleation and monomer droplets nucleation coexist in the presence of a water-soluble initiator but homogeneous nucleation becomes less significant with SDS concentration increasing. Meanwhile, using oil-soluble initiator, the possibility of homogeneous nucleation is depressed effectively. As a result, monomer droplets are definitely the main loci of particle nucleation.

Modified protein carbonyl assay detects oxidised membrane proteins: A new tool for assessing drug- and chemically-induced oxidative cell injury

Introduction: The carbonyl content of cell proteins is a useful indicator of oxidative protein damage during drug- and chemically-induced toxicities. Since a range of lipophilic carbonylating agents is produced during the membrane peroxidation that accompanies chemically-induced oxidative stress, integral membrane proteins seem especially vulnerable to adduction by these species. To develop tools for assessing such damage, this work refined a popular spectrophotometric assay so that hydrophobic and hydrophilic proteins are separated prior to carbonyl analysis. Methods: The low cloud point properties of Triton X114 were used to resolve mouse liver extracts into fractions comprising hydrophilic and hydrophobic proteins. Following phase separation, protein precipitation and removal of unwanted detergent was achieved via extraction with toluene containing 5% trichloroacetic acid. Carbonyl groups were derivatised using 2,4-dinitrophenylhydrazine and then quantified via spectrophotometry. Results: Postmitochondrial fractions from mouse liver were incubated with azo initiators that generate peroxyl radicals in respective phases of biphasic systems, namely the water-soluble initiator 2,2′-azobis(2-amidinopropane) hydrochloride (AAPH) and the lipophilic initiator 2,2′-azobis(2,4-dimethylvaleronitrile) (AMVN). Following resolution using Triton X114, the carbonyl content of hydrophilic proteins in controls was 1.5 ±0.1 nmol/mg protein, compared to 6.7 ± 0.57 nmol/mg protein in the corresponding hydrophobic proteins ( N = 3, p < 0.05). Exposure to AAPH for 2 h at 37 °C increased the carbonyl content of proteins in the hydrophilic and hydrophobic phases by 4.6- and 3.5-fold, respectively ( p < 0.05). AMVN produced a 3.3-fold increase in the carbonyl content of hydrophobic proteins ( p < 0.05) but did not alter that of aqueous phase proteins. Discussion: This method allows facile resolution of proteins into hydrophobic and hydrophilic fractions prior to carbonyl determination. This modified assay method may facilitate studies of the role of oxidative protein damage in drug- and chemically-induced toxic syndromes.

Puerarin and Conjugate Bases as Radical Scavengers and Antioxidants: Molecular Mechanism and Synergism with β-Carotene

The 4'-hydroxyl group of puerarin, a C-glycoside of the isoflavonoid daidzein, was shown, using 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radical cation and stopped-flow spectroscopy and by comparison with the 7-propylpuerarin (A ring derivative) and 4'-propylpuerarin (B ring derivative), to be a more efficient radical scavenger as compared to the 7-hydroxyl group by a factor of 2, a difference increasing upon deprotonation. The difference in radical scavenging agreed with the oxidation potentials (cyclic voltammetry in acetonitrile, 0.1 M Bu4NBF4 at 25 degrees C): E/mV=862+/-3 for puerarin, 905+/-10 for 7-propylpuerarin, and 1064+/-2 for 4'-propylpuerarin relative to ferrocene/ferricenium. In aqueous solution, the reduction potential was shown to decrease for increasing pH, and deprotonation of the 4'-hydroxyl group increased radical scavenging more than deprotonation of the 7-hydroxyl group. The 7-hydroxyl was found to be more acidic (pKa1=7.20+/-0.01 in puerarin and pKa=7.23+/-0.01 in 4'-propylpuerarin) than the 4'-hydroxyl group (pKa2=9.84+/-0.08 in puerarin and pKa=9.51+/-0.02 in 7-propylpuerarin); aqueous solution, ionic strength of 0.1, and 25 degrees C. In phosphatidyl choline liposome of pH 7.4, puerarin and beta-carotene each showed a modest antioxidant activity measured as prolongation of the lag phase for formation of conjugate dienes and using the water-soluble radical initiator APPH with effects of puerarin and beta-carotene being additive. For the lipophilic initiator AMVN, the antioxidative effect decreased for puerarin and increased for beta-carotene as compared to APPH and showed a clear synergism. A regeneration of beta-carotene, effective in the liposome lipid phase as antioxidant, from the cation radical by deprotonated forms of puerarin was demonstrated in 9:1 chloroform/methanol using laser flash photolysis with k2=2.7x10(4) L mol-1 s-1 for the bimolecular process between the cation radical and the puerarin dianion.

Polymerization of acrylonitrile using potassium peroxydisulfate as an initiator in the presence of a multisite phase-transfer catalyst: A kinetic study

In this article, the kinetics and mechanism of the free-radical polymerization of acrylonitrile (AN) using potassium peroxydisulfate (PDS) as a water-soluble initiator in the presence of synthesized 1,4-bis(triethyl methyl ammonium) benzene dichloride (DC-X) as a phase-transfer catalyst (PTC) were studied. The polymerization reactions were carried out under inert and unstirred conditions at a constant temperature of 60 ± 1°C in cyclohexane/water biphasic media. The rate of polymerization (Rp) increased with an increase in the concentrations of AN, PTC, and PDS. The order with respect to the monomer, initiator, and PTC was found to be 1.0, 0.5, and 0.5, respectively. Rp was independent of the ionic strength and pH of the medium. However, an increase in the polarity of the solvent slightly increased the Rp value. On the basis of the obtained results, a mechanism is proposed for the polymerization reaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Controlled preparation of nanocolorants via a modified miniemulsion polymerization process

Nanocolorants were successfully prepared via a modified miniemulsion polymerization process into which styrene, a polar monomer, crosslinkers, a highly hydrophobic solvent, dyes, and so forth were introduced. The obtained nanocolorants were nanocomposite entities in which a fraction of dye molecules attached to the crosslinked macromolecular chains and more dye molecules formed clustering because of the phase separation between the dye and polymer during the polymerization process and were further embedded in the interior of the crosslinked polymer because of the high hydrophobicity of the dyes. The effects of the polar monomers, the amounts of the dyes dissolved in styrene, and the polymer crosslinking, as well as the effects of the water-soluble and oil-soluble initiator, the amount of the surfactant, and the ultrasonic homogenization time, on the preserving fastness of the dyes in the polymeric matrix and the morphology and particle size distribution of the nanocolorants were studied.

Nanoparticle Formation by Monomer-Starved Semibatch Emulsion Polymerization

Latexes with very small particle size are usually manufactured by microemulsion polymerization. This article explains the preparation of nanolatexes by monomer-starved nucleation in a conventional semibatch emulsion polymerization with a low surfactant/monomer ratio and with no need for a cosurfactant. The semibatch emulsion polymerization reactions started with an aqueous solution of a surfactant and a water soluble initiator. Monomer was added at a fixed rate. The size of particles decreased with decreasing rate of monomer addition. High solids content nanolatexes with particles as small as 25 nm in diameter were produced. Several monomers with different water solubilities were compared. The order of the number of particles in terms of the rate of monomer addition was found to depend on the type of monomer. Water soluble monomers produced more particles due to associated chain transfer to monomer and radical exit. The monodispersity of particles at the end of nucleation increased as the rate of monomer addition decreased. The technique seems to be preferable to microemulsion polymerization, which uses a high concentration of surfactant/cosurfactant and is limited to low monomer holdup.

Impact of initiators in preparing magnetic polymer particles by miniemulsion polymerization

Sub-micron sized polystyrene particles containing magnetite more than 30 wt.% were prepared by miniemulsion polymerization with commercially available ferricolloid. The effects of some water-soluble initiators and/or oil-soluble initiators on the particles characteristics, such as the size, morphology, magnetic properties and colloidal stability, were studied. The size of monomer droplets/polymer particles increased from 60 to 300 nm during polymerization, keeping magnetic in core when potassium persulfate (KPS) or ammonium persulfate (APS) was used as the sole initiator. These particles were easily separated from the medium within short time scale in external magnetic field, while such characteristics were controlled by the amount of persulfate used for the polymerization. In contrast, when 2,2′-azobis isobutyronitrile (AIBN) was used as the initiator, the size of droplets/particles was retained to be 90 nm at the most and magnetite nanoparticles located at the surface of polystyrene particles, which were so colloidally stable that they were not separated in external magnetic field. The above-mentioned effect of initiators on particle size in persulfate system was likely originated from the decrease of pH value and the increase of ionic strength, which induced the fusion of droplets/particles containing magnetite. Mixed-initiators system resulted in intermediate characteristics, compared with each initiator system. The location of magnetite in the particle seems to depend on where initiation/polymerization occurred in each initiator system.

Botryoidal Assembly of Cholesteryl−Pullulan/Poly(N-isopropylacrylamide) Nanogels

Hybrid nanogels consisting of cholesteryl-modified pullulan (CHP) and poly(N-isopropylacrylamide) (PNIPAM) were synthesized by graft free-radical copolymerization of N-isopropylacrylamide (NIPAM) onto methacryloyl-substituted CHP nanogels (CHPMA) in water at 50 degrees C in the presence of a water-soluble free radical initiator. Depending on the initial NIPAM/CHPMA ratio, CHP-PNIPAM (CN) nanogels containing 30.8-84.8 wt % PNIPAM were obtained in the form of self-assembled nanoparticles with a hydrodynamic radius (Rh) of 69.0-116.0 nm in water kept at 20 degrees C. Hybrid nanogels of sufficiently high NIPAM content, such as the sample CN90, which contains 79.6 wt % NIPAM, exhibited a two-step response to changes in solution (3 mg/mL) temperature: a decrease in Rh from 93 to 57 nm as the temperature increased from 20 to 35 degrees C, followed by a sharp increase in Rh from 57 nm to 90 nm at 55 degrees C. Both steps in this temperature response were reversible. The multistep response to temperature of the CN nanogels was attributed to the morphology of the nanogels, which are seen as consisting of grape-like (botryoidal) clusters of associated native nanogels held together via cholesteryl cross-linking points and held together by the grafted PNIPAM chains.

Structure–activity relationship studies of resveratrol and its analogues by the reaction kinetics of low density lipoprotein peroxidation

Resveratrol (3,5,4′- trans-trihydroxystibene) is a natural phytoalexin present in grapes and red wine, which possesses a variety of biological activities including antioxidative activity. To find more active antioxidants, with resveratrol as the lead compound, we synthesized resveratrol analogues, i.e., 3,4,3′,4′-tetrahydroxy- trans-stilbene (3,4,3′,4′-THS), 3,4,4′-trihydroxy- trans-stilbene (3,4,4′-THS), 2,4,4′-trihydroxy- trans-stilbene (2,4,4′-THS), 3,3′-dimethoxy-4,4′-dihydroxy- trans-stilbene (3,3′-DM-4,4′-DHS), 3,4-dihydroxy- trans-stilbene (3,4-DHS), 4,4′-dihydroxy- trans-stilbene (4,4′-DHS), 3,5-dihydroxy- trans-stilbene (3,5-DHS) and 2,4-dihydroxy- trans-stilbene (2,4-DHS). Antioxidative effects of resveratrol and its analogues against free-radical-induced peroxidation of human low density lipoprotein (LDL) were studied. The peroxidation was initiated either by a water-soluble initiator 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH), or by cupric ion (Cu 2+). The reaction kinetics were monitored either by the uptake of oxygen and the depletion of α-tocopherol (TOH) presented in the native LDL, or by the formation of thiobarbituric acid reactive substances (TBARS). Kinetic analysis of the antioxidation process demonstrates that these trans-stilbene derivatives are effective antioxidants against both AAPH- and Cu 2+-induced LDL peroxidation with the activity sequence of 3,4,3′,4′-THS ∼ 3,3′-DM-4,4′-DHS > 3,4-DHS ∼ 3,4,4′-THS > 2,4,4′-THS > resveratrol ∼ 3,5-DHS > 4,4′-DHS ∼ 2,4-HS, and 3,4,3′,4′-THS ∼ 3,4-DHS ∼ 3,4,4′-THS > 3,3′-DM-4,4′-DHS > 4,4′-DHS > resveratrol ∼ 2,4-HS > 2,4,4′-THS ∼ 3,5-DHS, respectively. Molecules bearing ortho-dihydroxyl or 4-hydroxy-3-methoxyl groups possess significantly higher antioxidant activity than those bearing no such functionalities.

Highly Stable Polymerizable Vesicles in Anionic Surfactant/Ammonium Salt Mixtures in the Presence of Cross-linking Monomers for Convenient Preparation of Hollow Nanospheres

Spontaneous and stable vesicles are formed from vinylbenzyltrimethylammonium chloride (VBTAC) and sodium dodecyl sulfate (SDS) ranging in molar composition from 3:7 to 7:3 in the presence of 30 mol % divinylbenzene (DVB). Dynamic light scattering analysis and transmission electron microscope observations revealed that microparticles with diameters around 120 nm (30%) and 580 nm (70%) were formed. Trapping efficiency of the vesicles examined with D-(+)-glucose amounted to ca. 15%. These vesicles were capable of undergoing polymerization in the presence of water-soluble radical initiators such as 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride to fix the vesicular structure. Retention of the vesicle size and bimodal size distribution characteristics during the polymerization indicated that intravesicular polymerization prevailed over the intervesicular process. SDS was stably retained in the cross-linked vesicle and was not removed from the vesicle by exhaustive dialysis or ultrafiltration, due to the electrostatic interaction within the cross-linked polymeric framework produced from VBTAC and DVB. The resulting hollow nanospheres are readily redispersed in water without the aid of additional surfactants.

Antioxidant properties of natural carotenoid extracts against the AAPH-initiated oxidation of food emulsions

The antioxidant effects of natural carotenoid extracts on the oxidation of oil-in-water emulsions (initiated by a water-soluble radical initiator at 60 °C) were spectrophotometrically assessed at 233 nm. Headspace volatiles were also monitored for selected samples. At concentration of 1 g l − 1 the tested carotenoids significantly reduced the oxidative deterioration of sunflower oil-in-water emulsions. The presence of polar groups was found to modulate the carotenoid activity. Annatto extracts (orbiting and bixin) containing carotenoids with carboxylic and esters groups, were more effective than marigold extract containing lutein (with two hydroxyl groups). β-Carotene and a tomato (lycopene-rich) extract, (un-substituted carotenes), were the least effective. For polar carotenoids, the antioxidant activity did not increase with concentration above a specific level. The tested carotenoids strongly inhibited the formation of volatile aldehydes. Mixtures of lutein or β-carotene with tocopherol isomers increased the antioxidant activity of individual carotenoids. Mixtures of carotenoids with ascorbic acid at 0.1 g l − 1 exerted a tendency, not significant though, for increasing the activity of each individual carotenoid. Industrial relevance: The goal of this work was to develop a model for quality and storage stability determination of confectionary products using crystallization of sugar shell in hard panning process as example. The model developed can successfully predict the concentration profile and growth of sugar crystals in a thin film and it’s industrial relevance is evident by the industrial financial support.

Protective effects of endomorphins, endogenous opioid peptides in the brain, on human low density lipoprotein oxidation

Neurodegenerative disorders are associated with oxidative stress. Low density lipoprotein (LDL) exists in the brain and is especially sensitive to oxidative damage. Oxidative modification of LDL has been implicated in the pathogenesis of neurodegenerative diseases. Therefore, protecting LDL from oxidation may be essential in the brain. The antioxidative effects of endomorphin 1 (EM1) and endomorphin 2 (EM2), endogenous opioid peptides in the brain, on LDL oxidation has been investigated in vitro. The peroxidation was initiated by either copper ions or a water-soluble initiator 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH). Oxidation of the LDL lipid moiety was monitored by measuring conjugated dienes, thiobarbituric acid reactive substances, and the relative electrophoretic mobility. Low density lipoprotein oxidative modifications were assessed by evaluating apoB carbonylation and fragmentation. Endomorphins markedly and in a concentration-dependent manner inhibited Cu2+ and AAPH induced the oxidation of LDL, due to the free radical scavenging effects of endomorphins. In all assay systems, EM1 was more potent than EM2 and l-glutathione, a major intracellular water-soluble antioxidant. We propose that endomorphins provide protection against free radical-induced neurodegenerative disorders.

Encapsulation of magnetic nanoparticles with polystyrene via emulsifier-free miniemulsion polymerization

Magnetite nanoparticles (Fe 3O 4), with an average size of about 10 nm, were encapsulated with polystyrene using a new method based on emulsifier-free miniemulsion polymerization in the presence of 2, 2′ azobis (2-amidinopropane) dihydrochloride (V-50) as a cationic ionizable water-soluble initiator and hexadecane as a hydrophobe. Transmission electron microscopy (TEM) proved the presence of magnetite in polymer particles which appeared to be monodisperse in size, approximately 100–300 nm in diameter, through TEM and scanning electron microscopy (SEM). Thermogravimetric analysis (TGA) measurement was used to determine the percentage of magnetite in the products. The results of emulsifier-free miniemulsion polymerization were compared with those of conventional emulsifier-free emulsion polymerization using (V-50) as the initiator in both cases.

Miniemulsion Polymerization Stabilized by a Well-Defined, Amphiphilic Gradient Poly(styrene-co-acrylic acid) Copolymer

The nitroxide-mediated controlled free-radical copolymerization of styrene (St) and acrylic acid (AA) was used to synthesize a well-defined poly(St30%-co-AA70%) amphiphilic gradient copolymer. The latter proved to be an efficient stabilizer in the 45 wt.-% solids content, batch miniemulsion polymerizations of St and of mixtures of methyl methacrylate/n-butyl acrylate (35/65 w/w). With 2,2´-azobisisobutyronitrile as an oil-soluble initiator, polystyrene latexes with a very narrow particle distribution were obtained, whereas the water-soluble initiator, potassium persulfate, led to broad, multimodal particle size distributions. Such results were explained by the contribution of two nucleation mechanisms: droplet nucleation and homogeneous nucleation. In contrast, the poly(methyl methacrylate-co-n-butyl acrylate) latexes exhibited larger particle size and narrower particle size distributions with persulfate initiator, than the polystyrene latexes.

Particle size and size distribution of styrene/sulfopropylmethacrylate/2,2′-azobis[2-methyl-N-(2-hydroxyethyl) propionamide] (styrene/SPM/VA-086) and styrene/N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium betain [styrene/SPE/oil-soluble 1,1-azo-bis(cyclohexanecarbonitrile)]–initiated latices, using a zetasizer and atomic force microscopy

The preparation of surface-functional monodisperse nanoparticles with surfactant-free emulsion polymerization using polymerizable functional surface-active monomers was investigated. Crosslinked styrene seed latex to be used in the second-stage polymerization of styrene with SPM or SPE was synthesized. The seed latex was characterized by particle size and size distribution. In the second stage of a starved-feed polymerization of styrene with SPM, a water-soluble azo initiator and an oil-soluble azo initiator were used separately, and the relevant mechanistic characteristics, mainly competitive growth, were compared with data obtained from Zetasizer and atomic force microscopy measurements. The mechanism of competitive growth was the same in both systems. The oil-soluble azo initiator also was used in the second-stage, starved-feed polymerization of styrene with SPE. Latices were cleaned by the serum replacement technique and ion exchange method. Particle size data clearly suggested a bimodal particle size distribution during the first 2 h of polymerization. The bimodality originated from the fractions of different-sized particles in the seed latex competing for the available monomer. The two particle size fractions in the early stages of polymerization tended to merge after 2 h, a situation that satisfied the conditions of a competitive growth mechanism. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 166–174, 2006

RAFT-Mediated Emulsion Polymerization of Styrene using a Non-Ionic Surfactant

We report the successful RAFT-mediated emulsion polymerization of styrene using a non-ionic surfactant (Brij98), the highly reactive 1-phenylethyl phenyldithioacetate (PEPDTA) RAFT agent, and water-soluble initiator ammonium persulfate (APS). The molar ratio of RAFT agent to APS was identical in all experiments. Most of the monomer was contained within the micelles, analogous to microemulsion or miniemulsion systems but without the need of shear, sonication, cosurfactant, or a hydrophobe. The number-average molecular weight increased with conversion and the polydispersity index was below 1.2. This ideal ‘living’ behavior was only found when molecular weights of 9000 and below were targeted. It was postulated that the rapid transportation of RAFT agent from the monomer swollen micelles to the growing particles was fast on the polymerization timescale, and most if not all the RAFT agent is consumed within the first 10% conversion. In addition, it was postulated that the high nucleation rate from the high rate of exit (of the R radical from the RAFT agent) and high entry rate from water-phase radicals (high APS concentration) reduced the effects of ‘superswelling’ and therefore a similar molar ratio of RAFT agent to monomer was maintained in all growing particles. The high polydispersity indexes found when targeting molecular weights greater than 9000 were postulated to be due to the lower nucleation rate from the lower weight fractions of both APS and RAFT agent. In these cases, ‘superswelling’ played a dominant role leading to a heterogeneous distribution of RAFT to monomer ratios among the particles nucleated at different times.

OXIDATIVE STRESS-DEPENDENT CONVERSION OF HYDROGEN SULFIDE TO SULFITE BY ACTIVATED NEUTROPHILS

Sulfite, which is known as a major constituent of volcanic gas, is endogenously produced in mammals, and its concentration in serum is increased in patients with pneumonia. It has been reported that sulfite is produced by oxidation from hydrogen sulfide (H2S) as an intermediate in the mammalian body. The objective of this study was to investigate the ability of reactive oxygen species from neutrophils to produce sulfite from H2S. Sulfite production from activated neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine gradually increased with an increased concentration of sodium hydrosulfide (NaHS) in the medium. The production of sulfite was markedly suppressed with an NADPH oxidase inhibitor, diphenyleneiodonium. When NaHS was added to the supernatant of activated neutrophils, a significant amount of sulfite was synthesized in the test tubes. Furthermore, when a medium containing NaHS was incubated with a water-soluble radical initiator, 2,2'-azobis-(amidinopropane) dihydrochloride, sulfite was formed in the solution and this increase was markedly suppressed by ascorbic acid. Finally, we determined serum concentrations of sulfite and H2S in an in vivo model of neutrophil activation induced by systemic injection of lipopolysaccharide (LPS) into rats. We found a significant increase in serum sulfite and H2S after LPS injection. Importantly, coadministration of ascorbic acid with LPS further increased serum H2S but suppressed sulfite levels. This finding implies that oxidative stress-dependent conversion of H2S to sulfite might occur in vivo. Thus, the oxidation of H2S is a novel sulfite production pathway in the inflammatory condition, and this chemical synthesis might be responsible for the upregulation of sulfite production in inflammatory conditions such as pneumonia.

HYDROGEN SULFIDE AND SULFITE: NOVEL MEDIATORS IN THE PATHOPHYSIOLOGY OF SHOCK AND INFLAMMATION

HYDROGEN SULFIDE AND SULFITE: NOVEL MEDIATORS IN THE PATHOPHYSIOLOGY OF SHOCK AND INFLAMMATION

Protective effects of flavonols and their glycosides against free radical-induced oxidative hemolysis of red blood cells

The in vitro oxidative hemolysis of human red blood cells (RBCs) was used as a model to study the free radical-induced damage of biological membranes and the protective effect of flavonols and their glycosides (FOHs), i.e., myricetin (MY), quercetin (Q), morin (MO), kaempferol (K), rutin (R), quercetin galactopyranoside (QG), quercetin rhamnopyranoside (QR), and kaempferol glucopyranoside (KG). The hemolysis of RBCs was induced by a water-soluble free radical initiator 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH). It was found that addition of AAPH at 37 °C to the suspension of RBCs caused fast hemolysis after a short period of inhibition period, and addition of FOHs significantly suppressed the hemolysis. The FOHs (MY, Q, R, QG and QR) which bears an ortho-dihydroxyl functionality showed much more effective anti-hemolysis activity than that of the other FOHs (MO, K and KG) bearing no such functionality.