- Development and Application of a Peroxyl Radical Clock Approach for Measuring Both Hydrogen-Atom Transfer and Peroxyl Radical Addition Rate Constants
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The rate-determining step in free radical lipid peroxidation is the propagation of the peroxyl radical, where generally two types of reactions occur: (a) hydrogen-atom transfer (HAT) from a donor to the peroxyl radical; (b) peroxyl radical addition (PRA) to a C=C double bond. Peroxyl radical clocks have been used to determine the rate constants of HAT reactions (kH), but no radical clock is available to measure the rate constants of PRA reactions (kadd). In this work, we modified the analytical approach on the linoleate-based peroxyl radical clock to enable the simultaneous measurement of both kH and kadd. Compared to the original approach, this new approach involves the use of a strong reducing agent, LiAlH4, to completely reduce both HAT and PRA-derived products and the relative quantitation of total linoleate oxidation products with or without reduction. The new approach was then applied to measuring the kH and kadd values for several series of organic substrates, including para- and meta-substituted styrenes, substituted conjugated dienes, and cyclic alkenes. Furthermore, the kH and kadd values for a variety of biologically important lipids were determined for the first time, including conjugated fatty acids, sterols, coenzyme Q10, and lipophilic vitamins, such as vitamins D3 and A.
- Do, Quynh,Lee, David D.,Dinh, Andrew N.,Seguin, Ryan P.,Zhang, Rutan,Xu, Libin
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supporting information
p. 153 - 168
(2020/12/23)
-
- Catalytic production of oxo-fatty acids by lipoxygenases is mediated by the radical-radical dismutation between fatty acid alkoxyl radicals and fatty acid peroxyl radicals in fatty acid assembly
-
Oxo-octadecadienoic acids (OxoODEs) act as peroxisome proliferator-activated receptor (PPAR) agonists biologically, and are known to be produced in the lipoxygenase/linoleate system. OxoODEs seem to originate from the linoleate alkoxyl radicals that are generated from (E/Z)-hydroperoxy octadecadienoic acids ((E/Z)HpODEs) by a pseudoperoxidase reaction that is catalyzed by ferrous lipoxygenase. However, the mechanism underlying the conversion of alkoxyl radical into OxoODE remains obscure. In the present study, we confirmed that OxoODEs are produced in the lipoxygenase/linoleate system in an oxygen-dependent manner. Interestingly, we revealed a correlation between the (E/Z)-OxoODEs content and the (E/E)-HpODEs content in the system. (E/E)-HpODEs could have been derived from (E/E)-linoleate peroxyl radicals, which are generated by the reaction between a free linoleate allyl radical and an oxygen molecule. Notably, the ferrous lipoxygenase-linoleate allyl radical (LOx(Fe2+)-L·) complex, which is an intermediate in the lipoxygenase/linoleate system, tends to dissociate into LOx(Fe2+) and a linoleate allyl radical. Subsequently, LOx(Fe2+) converts (E/Z)-HpODEs to an (E/Z)-linoleate alkoxyl radical through one-electron reduction. Taken together, we propose that (E/Z)-OxoODEs and (E/E)-HpODEs are produced through radical-radical dismutation between (E/Z)-linoleate alkoxyl radical and (E/E)-linoleate peroxyl radical. Furthermore, the production of (E/Z)OxoODEs and (E/E)-HpODEs was remarkably inhibited by a hydrophobic radical scavenger, 2,2,6,6-tetra-methylpiperidine 1-oxyl (TEMPO). On the contrary, water-miscible radical scavengers, 4-hydroxyl-2,2,6,6-tetramethylpiperidine 1-oxyl (OH-TEMPO) and 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrroline-N-oxyl (CmΔP) only modestly or sparingly inhibited the production of (E/Z)-OxoODEs and (E/E)-HpODEs. These facts indicate that the radical-radical dismutation between linoleate alkoxyl radical and linoleate peroxyl radical proceeds in the interior of micelles.
- Takigawa, Yuta,Koshiishi, Ichiro
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p. 258 - 264
(2020/11/26)
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- Ascorbic acid 6-palmitate: A potent inhibitor of human and soybean lipoxygenase-dependent lipid peroxidation
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Objectives Lipoxygenases (LOX) are the key enzymes involved in the biosynthesis of leukotrienes and reactive oxygen species, which are implicated in pathophysiology of inflammatory disorders. This study was conducted to evaluate the inhibitory effect of water-soluble antioxidant ascorbic acid and its lipophilic derivative, ascorbic acid 6-palmitate (Vcpal) on polymorphonuclear lymphocyte 5-LOX and soybean 15-LOX (sLOX) in vitro. Methods LOX activity was determined by measuring the end products, 5-hydroperoxy eicosatetraenoic acid (5-HETE) and lipid hydroperoxides, by spectrophotometric and high performance liquid chromatography methods. The substrate-dependent enzyme kinetics and docking studies were carried out to understand the nature of inhibition. Key findings Vcpal potently inhibited 5-LOX when compared with its inhibitory effect on sLOX (IC50; 2.5 and 10.3μm respectively, P= 0.003). Further, Vcpal inhibited 5-LOX more strongly than the known synthetic drugs: phenidone and nordihydroguaiaretic acid (P= 0.0007). Enzyme kinetic studies demonstrated Vcpal as a non-competitive reversible inhibitor of 5-LOX. In-silico molecular docking revealed high MolDock and Rerank score for Vcpal than ascorbic acid, complementing in-vitro results. Conclusion Both in-vitro and docking studies demonstrated Vcpal but not ascorbic acid as a non-competitive inhibitor of 5-LOX- and sLOX-induced lipid peroxidation, suggesting a key role for lipophilic nature in bringing about inhibition.
- Mohamed, Riyaz,Tarannum, Shaista,Yariswamy, Manjunath,Vivek, Hamse K.,Siddesha, Jalahalli M.,Angaswamy, Nataraju,Vishwanath, Bannikuppe S.
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p. 769 - 778
(2014/06/09)
-
- In vitro inhibition of linoleic acid peroxidation by primary S-Nitrosothiols
-
Nitric oxide (*NO) is an effective chain-breaking antioxidant in the inhibition of lipid peroxidation and circulates in vivo mainly as primary S-nitrosothiols (RSNOs). In this work, the in vitro peroxidation of linoleic acid-SDS comicelles (LA-SDS) catalyzed by soybean lipoxygenase (SLO) and Fe II ions was monitored in the presence and absence of three primary RSNOs: S-nitrosocysteine, S-nitroso-N-acetylcysteyne and S-nitrosoglutathione. Kinetic measurements based on the formation of conjugated double bonds and fluorescent oxidized LA-lysine adducts, showed that RSNOs are more potent antioxidants than their corresponding free thiols (RSHs) in equimolar conditions. These results are consistent with the blocking of LA-SDS peroxidation by RSNOs through the inactivation of peroxyl/alkoxyl (LOO*/LO*) radicals, leading to nitrogen-containing products of oxidized LA, which release free *NO. These results indicate that endogenous RSNOs may play a major role in the blocking of lipid peroxidation in vivo, through the primary inactivation of alkoxyl/peroxyl radicals and also of preformed lipid hydroperoxides.
- Simplicio, Fernanda I.,Seabra, Amedea B.,De Souza, Gabriela F. P.,De Oliveira, Marcelo G.
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experimental part
p. 1885 - 1895
(2011/01/12)
-
- Proteins modified by the lipid peroxidation aldehyde 9,12-dioxo-10(E)- dodecenoic acid in MCF7 breast cancer cells
-
The hydroperoxide of linoleic acid (13-HPODE) degrades to 9,12-dioxo-10(E)-dodecenoic acid (DODE), which readily modifies proteins. This study identified the major proteins in MCF7 cells modified by DODE. To reduce false positives, three methods were used to identify DODE-modified proteins. First, cells were treated with a synthetically biotinylated 13-HPODE (13-HPODE-biotin). Modified proteins were enriched by neutravidin affinity and identified by two-dimensional liquid chromatography-tandem mass spectrometry (2D LC-MS/MS). Second, cells were treated with native 13-HPODE. Protein carbonyls were biotinylated with an aldehyde reactive probe, and modified proteins were enriched by neutravidin affinity and identified by 2D LC-MS/MS. Third, using a newly developed DODE antibody, DODEmodified proteins were located by 2D sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot and identified by in-gel digestion and LC-MS/MS. Analysis of the proteins characterized by all three methods revealed a significant overlap and identified 32 primary proteins modified by DODE in MCF7 cells. These results demonstrated the feasibility for the cellular formation of DODE protein-carbonyl adducts that may be future indicators of oxidative stress.
- Slade, Peter G.,Williams, Michelle V.,Brahmbhatt, Viral,Dash, Ajit,Wishnok, John S.,Tannenbaum, Steven R.
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experimental part
p. 557 - 567
(2011/02/24)
-
- Quantitation of hydroperoxy-, keto- and hydroxy-dienes during oxidation of FAMEs from high-linoleic and high-oleic sunflower oils
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The objective of this work was to study the quantitative formation of hydroperoxydienes, ketodienes and hydroxydienes during autoxidation at 40 °C of fatty acid methyl esters derived from two sunflower oils with different degree of unsaturation, high-linoleic sunflower oil and high-oleic sunflower oil. The analysis of the oxidation compounds was carried out by NP-HPLC-UV and results were compared to the specific extinction at 232 nm (K 232) and the peroxide value (PV). Analysis of FAME polymers by HPSEC was also performed to discard samples of advanced oxidation. Results showed that the contents of hydroperoxydienes with respect to the PV were higher for the high linoleic (HL) sample. At the end of the period of slow polymerization (ΔPol ≤ 1 wt%), the content of hydroperoxydienes was found to be 86.0 and 30.7 μg/mg for the HL and high oleic (HO) samples, respectively. Throughout this period, hydroperoxydienes constituted around 90 and 50 wt% of the total hydroperoxides in the HL and HO samples, respectively, suggesting that a significant oxidation of oleic acid also occurred in both samples. The contents of ketodienes and hydroxydienes as a whole constituted 2-3 wt% of the diene compounds analyzed at the end of the period of slow polymerization. Higher contents of ketodienes than of hydroxydienes were found throughout the oxidation time, and the ratio between the contents of ketodienes and hydroxydienes increased with a factor that changed from 1 to 2 throughout the period of slow polymerization.
- Morales, Arturo,Dobarganes, Carmen,Marquez-Ruiz, Gloria,Velasco, Joaquin
-
experimental part
p. 1271 - 1279
(2011/08/21)
-
- Rate constants for peroxidation of polyunsaturated fatty acids and sterols in solution and in liposomes
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Rate constants for autoxidation propagation of several unsaturated lipids in benzene solution at 37°C and in phosphatidylcholine liposomes were determined by a linoleate radical clock. This radical clock is based on competition between hydrogen atom abstraction by an intermediate peroxyl radical derived from linoleic acid that leads to a trans,cis-conjugated hydroxyoctadecadienoic product and β-fragmentation of the same peroxyl that gives the trans,trans-product hydroxyoctadecadienoic acid. Rate constants determined by this approach in solution relative to linoleic acid (k p) 62 M-1 s-1) were: arachidonic acid (k p = 197 ± 13 M-1 s-1), eicosapentaenoic acid (kp = 249 ± 16 M-1 s-1), docosahexaenoic acid (kp = 334 ± 37 M-1 s -1), cholesterol (kp= 11 ± 2 M-1 s -1), and 7-dehydrocholesterol (kp = 2260 ± 40 M-1 s-1). Free radical oxidations of multilamellar and unilamellar liposomes of various mixtures of glycerophosphatidylcholine molecular species were also carried out. In some experiments, cholesterol or 7-dehydrocholesterol was incorporated into the lipid mixture undergoing oxidation. A phosphatidylcholine bearing a linoleate ester at sn-2 was a component of each liposome peroxidation reaction and the ratio of trans,cis/trans,trans (t,c/t,t)-conjugated diene oxidation products formed from this phospholipid was determined for each oxidation reaction. This t,c/t,t-product ratio from linoleate was used to "clock" liposome constituents as hydrogen atom donors in the lipid bilayer. Application of this lipid bilayer radical clock gives relative autoxidation propagation rate constants of arachidonate (20:4), eicosapentaenoate (20:5), docosahexaenoate (22:6), and 7-dehydrocholesterol to be 115 ± 7, 145 ± 8, 172 ± 13, and 832 ± 86, respectively, a reactivity trend that parallels the one in solution. We also conclude from the liposome oxidations that linoleate peroxyl radicals at different positions on the eighteen-carbon chain (at C-9 and C-13) have different kinetic properties. This is in contrast to the results of solution oxidations of linoleate in which the C-9 and C-13 peroxyl radicals have similar reactivities. We suggest that peroxyl radical β-scission depends on solvent polarity and the polarity of the local environment of peroxyl radicals in liposomal oxidations depends on the position of the peroxyl radical on the 18-carbon chain.
- Xu, Libin,Davis, Todd A.,Porter, Ned A.
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experimental part
p. 13037 - 13044
(2009/12/08)
-
- Physcomitrella patens has lipoxygenases for both eicosanoid and octadecanoid pathways
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Mosses have substantial amounts of long chain C20 polyunsaturated fatty acids, such as arachidonic and eicosapentaenoic acid, in addition to the shorter chain C18 α-linolenic and linoleic acids, which are typical substrates of lipoxygenases in flowering p
- Anterola, Aldwin,G?bel, Cornelia,Hornung, Ellen,Sellhorn, George,Feussner, Ivo,Grimes, Howard
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experimental part
p. 40 - 52
(2009/07/11)
-
- Antioxidative activities of galloyl glucopyranosides from the stem-bark of Juglans mandshurica
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Two phenolics, 1,2,6-trigalloylglucose (1) and 1,2,3,6-tetragalloylglucose (2), isolated from the stem-bark of Juglans mandshurica were evaluated for their antioxidative activities. The results showed that compounds 1 and 2 exhibited strong scavenging activities against 1,1′-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis-(3-ethylbenzenthiazoline-6-sulphonic) acid (ABTS?+), and superoxide radicals (O2 ?-), and also had a significant inhibitory effect on lipid peroxidation and low-density lipoprotein (LDL) oxidation. The strong superoxide radical scavenging of 1 and 2 resulted from the potential competitive inhibition with xanthine at the active site of xanthine oxidase (OX). In addition, compounds 1 and 2 displayed significant lipoxygenase inhibitory activity, the mode of inhibition also being identified as competitive. In comparison, the antioxidative activities of compounds 1 and 2, together with gallic acid, indicated that the number of galloyl moieties could play an important role in the antioxidative activity.
- Ngoc, Tran Minh,Hung, Tran Manh,Thuong, Phuong Thien,Kim, Jin-Cheon,Choi, Jae Sue,Bae, Kihwan,Hattori, Masao,Choi, Chung-Sig,Lee, Joon Seok,Min, Byung-Sun
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p. 2158 - 2163
(2008/12/23)
-
- Properties of a mini 9R-lipoxygenase from Nostoc sp. PCC 7120 and its mutant forms
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Lipoxygenases (LOXs) consist of a class of enzymes that catalyze the regio- and stereospecific dioxygenation of polyunsaturated fatty acids. Current reports propose that a conserved glycine residue in the active site of R-lipoxygenases and an alanine residue at the corresponding position in S-lipoxygenases play a crucial role in determining the stereochemistry of the product. Recently, a bifunctional lipoxygenase with a linoleate diol synthase activity from Nostoc sp. PCC7120 with R stereospecificity and the so far unique feature of carrying an alanine instead of the conserved glycine in the position of the sequence determinant for chiral specificity was identified. The recombinant carboxy-terminal domain was purified after expression in Escherichia coli. The ability of the enzyme to use linoleic acid esterified to a bulky phosphatidylcholine molecule as a substrate suggested a tail-fist binding orientation of the substrate. Site directed mutagenesis of the alanine to glycine did not cause alterations in the stereospecificity of the products, while mutation of the alanine to valine or isoleucine modified both regio- and enantioselectivity of the enzyme. Kinetic measurements revealed that substitution of Ala by Gly or Val did not significantly influence the reaction characteristics, while the A162I mutant showed a reduced vmax. Based on the mutagenesis data obtained, we suggest that the existing model for stereocontrol of the lipoxygenase reaction may be expanded to include enzymes that seem to have in general a smaller amino acid in R and a bulkier one in S lipoxygenases at the position that controls stereospecificity.
- Andreou, Alexandra-Zoi,Vanko, Marian,Bezakova, Lydia,Feussner, Ivo
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p. 1832 - 1837
(2008/09/20)
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- Regiochemical and stereochemical evidence for enzyme-initiated catalysis in dual positional specific maize lipoxygenase-1
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Dual positional specific maize lipoxygenase-1 catalyzed the formation of racemic mixtures of four possible regioisomers and was strongly inhibited by the radical scavenger, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinoxy radical. Molecular modeling studies indicated that the oxygen-binding cavity is segregated from the substrate-binding cavity. The data suggest that a bis-allylic radical reaction intermediate is generated enzymatically, released from the enzyme active site, and subsequently oxygenated outside of the enzyme active site by a nonenzymatic mechanism.
- Jang, Sungkuk,Huon, Thavrak,Kim, Keumhwa,Um, Eunji,Han, Oksoo
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p. 3113 - 3116
(2008/02/10)
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- Linoleic acid 10-hydroperoxide as an intermediate during formation of 1-octen-3-ol from linoleic acid in Lentinus decadetes.
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In order to confirm the biosynthetic pathway to 1-octen-3-ol from linoleic acid, a crude enzyme solution was prepared from the edible mushroom, Lentinus decadetes. When the reaction was performed in the presence of glutathione peroxidase, which can reduce
- Matsui, Kenji,Sasahara, Satomi,Akakabe, Yoshihiko,Kajiwara, Tadahiko
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p. 2280 - 2282
(2007/10/03)
-
- Mechanism of lipid peroxidation photosensitized by tiaprofenic acid: Product studies using linoleic acid and 1,4-Cyclohexadienes as model substrates
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A careful study of the linoleic acid hydroperoxide (LOOH) profile obtained upon peroxidation of linoleic acid (LA) photosensitized by tiaprofenic acid (TPA) and analogous ketones has been undertaken to distinguish between type-I and type-II photoperoxidation mechanisms. 1,4-Cyclohexadiene and 1,2-dimethylcyclohexa-2,5-diene-carboxylic acid (CHDCA) have also been used as models for LA since they also have double allylic systems. Coir-radiation of LA with TPA and decarboxytiaprofenic acid (DTPA) in acetonitrile and micellar media produced significant amounts of conjugated dienic LOOH. The cis,trans to trans,trans ratio depended on the irradiation time; thus, this parameter is an ambiguous tool for mechanistic assignment. An interesting finding was the decrease of the LOOH level after long irradiation times in mixtures photooxidized by DTPA, which is attributed to quenching of the DTPA triplet by the generated dienic LOOH. High-performance liquid chromatography analyses confirmed that the main pathway operating in photodynamic lipid peroxidation sensitized by (D)TPA is a type-I mechanism. However, product studies using CHDCA have clearly shown that a type-II mechanism is also operating and might contribute to the overall photooxidation process in a significant way.
- Samadi, Abdelouahid,Martinez, Luis A.,Miranda, Miguel A.,Morera, Isabel M.
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p. 359 - 365
(2007/10/03)
-
- Antioxidant activities of major components of γ-oryzanol from rice bran using a linoleic acid model
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The change in hydroperoxides of linoleic acid incubated with constant micro air flow at 37°C was used to evaluate the antioxidant activities of three major components of γ-oryzanol from rice bran (cycloartenyl ferulate, 24-methylene cycloartanyl ferulate, and campesteryl ferulate) compared with α-tocopherol and ferulic acid. The four hydroperoxide isomers of linoleic acid, 9-hydroperoxy-10-trans, 12-cis-octadecadienoic acid [9HPODE(t,c)], 9-hydroperoxy-10-trans,12-trans-octadecadienoic acid, 13-hydroperoxy-9-cis, 11-trans-octadecadienoic acid [13HPODE(c,t)], and 13-hydroperoxy-9-trans, 11-trans-octadecadienoic acid, were measured using normal-phase high-performance liquid chromatography with an ultraviolet detector. The three components of γ-oryzanol evidenced significant antioxidant activity when they were mixed with linoleic acid in a molar ratio of 1:100 and 1:250 but not in a molar ratio of 1:500 (P 0.05). α-Tocopherol and ferulic acid also demonstrated significant antioxidant activity at all three molar ratios (P 0.05). The highest molar ratio (1:100) of α-tocopherol, however, caused greater levels of 9HPODE(t,c) and 13HPODE(c,t) than the other two less concentrated treatments.
- Xu,Samuel Godber
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p. 645 - 649
(2007/10/03)
-
- Quantitative HPLC determination of the antioxidant activity of capsaicin on the formation of lipid hydroperoxides of linoleic acid: A comparative study against BHT and melatonin
-
The antioxidant activity of capsaicin, as compared to BHT and melatonin, was determined by the direct measurement of lipid hydroperoxides formed upon linoleic acid autoxidation initiated by AIBN. The formation of four isomeric lipid hydroperoxides was detected after reverse-phase HPLC separation. Data from three detectors, UV absorption, glassy carbon electrode electrochemical detection, and postcolumn chemiluminescence using luminol, were compared. Capsaicin was more effective than melatonin in suppressing the formation of lipid hydroperoxides but not as effective as BHT. The formation of capsaicin and BHT dimers was observed during oxidation, and the dimers were characterized using APCI MS(n).
- Henderson, David E.,Slickman, Adam M.,Henderson, Susan K.
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p. 2563 - 2570
(2007/10/03)
-
- Retinoic acid-dependent stimulation of 2,2'-azobis(2-amidinopropane)- initiated autoxidation of linoleic acid in sodium dodecyl sulfate micelles: A novel prooxidant effect of retinoic acid
-
(E)-Retinoic acid (RA) was shown to stimulate the rate of 2,2'-azobis(2- amidinopropane) (AAPH)-initiated autoxidation of linoleic acid (18:2) in sodium dodecyl sulfate (SDS) micelles. RA-dependent stimulation of 18:2 autoxidation was characterized by enhanced rates of dioxygen uptake which were linear with retinoid concentration. In contrast, 5,6-epoxy-RA, a major oxidation product of RA, failed to affect the rate of dioxygen consumption at all concentrations tested. RA was also shown to stimulate peroxyl radical- dependent oxidation of styrene to the corresponding oxirane when styrene was included in the micellar system as a molecular probe. Furthermore, unequivocal evidence of RA-dependent stimulation of 18:2 autoxidation was obtained by relative quantitation of 13-hydroxy-(9Z, 11E)-octadecadienoic acid (13-HODE) plus 9-hydroxy-(10E,12Z)-octadecadienoic acid (9-HODE) production. In addition, enhanced carboncentered radical formation was demonstrated in the presence of RA by EPR spectroscopy using α-(4-pyridyl 1- oxide)-N-tert-butylnitrone (4-POBN) as a spin trap. Analysis and quantitation of RA oxidation products indicated that RA was oxidized to one primary product, 5,6-epoxy-RA, which was identified on the basis of cochromatography with synthetic standard (in a reverse-phase HPLC system), electronic absorption spectroscopy, and positive chemical ionization mass spectrometry of the corresponding methyl ester. Other minor oxidation products were also detected but not characterized. In contrast, reaction mixtures devoid of 18:2 failed to demonstrate significant retinoid oxidation. Mechanisms are proposed to account for the prooxidant effects of RA in this system.
- Freyaldenhoven, Mary Ann,Lehman, Paul A.,Franz, Thomas J.,Lloyd, Roger V.,Samokyszyn, Victor M.
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p. 102 - 110
(2007/10/03)
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- Iron-mediated generation of the neurotoxin 6-hydroxydopamine quinone by reaction of fatty acid hydroperoxides with dopamine: A possible contributory mechanism for neuronal degeneration in parkinson's disease
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Exposure of dopamine to an excess of linoleic acid 13-hydroperoxide (13- hydroperoxyoetadecadienoic acid) in the presence of ferrous ions in Tris buffer, pH 7.4, resulted in a relatively fast, oxygen-independent reaction exhibiting first-order kinetics wi
- Pezzella, Alessandro,D'Ischia, Marco,Napolitano, Alessandra,Misuraca, Giovanna,Prota, Giuseppe
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p. 2211 - 2216
(2007/10/03)
-
- Preparative Separation and 1H NMR Identification of Products of Linoleic Acid Autooxidation
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Bulk phase oxidation of linoleic acid in a diffuse system in the dark at 2-5 deg C was found to produce three types of oxygenated derivatives.An effective method of HPLC on the nitrile phase was developed for the analysis and preparative isolation of products, which made it possible to prepare individual structural isomers of each type.After preliminary identification by chemical, chromatographic, and UV methods, the isolated compounds were identified as 9- and 13-isomers of hydroperoxy-, hydroxy-, and ketooctadecadienoic acids with Z-E-conjugated double bond systems.The formation of minor E-E-regioisomers of linoleic acid hydroperoxides was also observed.The assignment of signals in the 1H NMR spectra of the compounds isolated, including homonuclear proton-decoupled spectra, validated the proposed structures.It is suggested that the preferable formation of Z-E-isomers of oxygenated products during linoleic acid autooxidation under low temperature is connected with impossibility of overcoming the energy barrier of primary peroxyradical isomerization.Key words: polyunsaturated fatty acids, peroxidation, isolation and identification of products, high-performance liquid chromatography (HPLC), 1H NMR spectroscopy
- Chudinova, V. V.,Chudinov, M. V.,Eremin, S. V.,Alekseev, S. M.
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p. 470 - 477
(2007/10/03)
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- High-Performance Liquid Chromatographic Analysis of the Products of Linoleic Acid Oxidation Catalyzed by Pea (Pisum sativum) Seed Lipoxygenases
-
An HPLC method is discussed for the analysis of the products formed by the pea (Pisum sativum) lipoxygenase catalyzed oxidation of linoleic acid.The results demonstrate the feasibility of analyzing all of the hydroperoxides, hydroxides, and keto fatty acids in a single chromatographic step and show that it will be possible to analyze the product profile from the lipoxygenase activity contained in a portion of a seed, which will permit the remainder of the seed to be grown on for subsequent generations.The chemical structures of the products have been identified by HPLC analysis and GC-MS. Keywords: Lipoxygenase; hydroperoxides; chromatography
- Wu, Zecai,Robinson, David S.,Domoney, Claire,Casey, Rod
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p. 337 - 342
(2007/10/02)
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- Auto-growth inhibitory substance from the fresh-water cyanobacterium Phormidium tenue
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An extract of the cyanobacterium P. tenue showed a significant inhibitory effect on its own growth. Bioassay-directed fractionation has led to the identification of the auto-growth inhibitory substance as a mixture of fatty acids. Unsaturated fatty acids such as linoleic and linolenic acids appear to be predominantly responsible for the auto-growth inhibitory effect.
- Yamada,Murakami,Morimoto,Sakakibara
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p. 1863 - 1865
(2007/10/02)
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- Isomerization of Linoleic Acid Hydroperoxides under Argon and under Degassed Conditions
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The rearrangement of linoleic acid hydroperoxides, (9Z,11E)-13-hydroperoxy-9,11- and (9E,11E)-13-hydroperoxy-9,11-octadecadienoic acids (13-Z,E-LOOH and 13-E,E-LOOH, respectively), occurred under argon and under degassed conditions, as well as under aerobic conditions.In argon-saturated benzene, 13-Z,E-LOOH isomerized to 9-E,E- and 13-E,E-LOOHs, and 13-E,E-LOOH to 9-E,E-LOOH; the E,E-isomers hardly isomerized to E,Z-isomers.The hydroperoxides isomerized rapidly in benzene and chloroform, but slowly in n-propyl ether and methanol.However, they decomposed extensively in chloroform, and moderately in benzene and methanol.Decomposition was very slight in n-propyl ether.The isomerization rate of the 9Z,11E-isomer was much higher than that of the 9E,11E-isomer.Since the rate was found to be slow under degassed conditions, traces of dissolved molecular oxygen may be responsible for the isomerization.Keywords - linoleic acid hydroperoxide; rearrangement; isomerization; solvent effect; molecular oxygen; HPLC
- Kaneko, Takao,Matsuo, Mitsuyoshi
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p. 332 - 335
(2007/10/02)
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- Unified Mechanism for Polyunsaturated Fatty Acid Autooxidation. Competition of Peroxy Radical Hydrogen Atom Abstraction, β-Scission, and Cyclization
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The autooxidation of linoleic (18:2) and arachidonic (20:4) acids with several cosubstrates was investigated.Cumene, tetralin, 1,4-cyclohexadiene, and 9,10-dihydroanthracene in benzene were used as cosubstrates for the oxidation of linoleic acid.The distribution of products, trans,cis diene hydroperoxides and trans,trans diene hydroperoxides, was dependent on the ability of cosubstrates to donate hydrogen atoms to linoleate peroxy radicals.Arachidonic acid was oxidized in mixtures of benzene/1,4-cyclohexadiene with linoleic acid internal standard.Product distribution of six hydroperoxyeicosatetraenoic acids (HPETE) derived from arachidonic acid was established at different concentrations of 1,4-cyclohexadiene in the solvent mixture.A kinetic expression is derived that is useful in describing polyunsaturated fatty acid oxidation product mixtures.By the use of this kinetic derivation, the rate of cyclization of peroxy free radicals derived from arachidonic acid was determined.
- Porter, Ned A.,Lehman, Laura S.,Weber, Bruce A.,Smith, Karl J.
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p. 6447 - 6455
(2007/10/02)
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- Autoxidation of Polyunsaturated Lipids. Factors Controlling the Stereochemistry of Product Hydroperoxides
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The mechanism of the autoxidation of linoleic acid and phospholipid esters of this acid was investigated.The products of autoxidation,13-hydroperoxy-9-cis,11-trans-octadecadienoic (4), 13-hydroperoxy-9-trans,11-trans-octadecadienoic (5), 9-hydroperoxy-10-
- Porter, Ned A.,Weber, Bruce A.,Weenen, Hugo,Khan, Jamil A.
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p. 5597 - 5601
(2007/10/02)
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