Linoleic Oxidation Research Articles

New fatty dihydropyridines present cardioprotective potential in H9c2 cardioblasts submitted to simulated ischemia and reperfusion

Nifedipine is a calcium channel blocker dihydropyridine that has been used in the treatment of hypertension. The production of reactive species and calcium overload are the main contributors to myocardial ischemia-reperfusion (I / R) injury. We investigated the ability of novel dihydropyridines (DHPs) to improve the effect of protecting against the injury induced by ischemia and reperfusion in cardioblasts when compared to nifedipine. Forty three DHPs were created varying the fatty chains derived from palmitic acid, stearic acid and oleic acids and aromatic moiety in addition to the addition of chemical elements such as chlorine, nitrogen dioxide, furfural, hydroxyl and methoxy. Cytotoxicity and inhibition of linoleic oxidation were evaluated for all new DHPs and also for nifedipine. The alpha-tocopherol and butylated hydroxytoluene (BHT) were used as antioxidants controls. The compounds with the best antioxidant potential were used in the ischemia and reperfusion (I / R) induction test in cardioblasts (H9c2). Cardioblasts were treated 24 h after assembly of plates and submitted to the ischemia simulation (30 min), after which, normoxia and cellular nutrition conditions were reestablished, simulating reperfusion (additional 30 min). Right after, cell viability, apoptosis, necrosis, and the generation of reactive oxygen species (ROS) were evaluated. Cell viability during I / R was not altered in cells treated with nifedipine, BHT and the new DHP composed of palmitic acid with hydroxyl group in the aromatic substituent. The other new DHPs increased cell viability during I / R simulation and reduced levels of reactive species compared to the I / R group, demonstrating the antioxidant capacity of the new DHPs. Therefore, DHPS with palmitic and oleic acids in the C3 and C5 position with NO2 or Cl in aromatic moiety, presented the highest antioxidant potential (linoleic oxidant test). The new DHPs increased cell viability during I / R simulation and reduced levels of reactive species compared to the ischemia and reperfusion group, demonstrating the antioxidant capacity of the new DHPs. Taken together, these results indicate that those new DHPs have a greater cardioprotective antioxidant capacity to face the damages of ischemia and reperfusion.

New Insights on the Oxidation of Unsaturated Fatty Acid Methyl Esters Catalyzed by Niobium(V) Oxide. A Study of the Catalyst Surface Reactivity

The catalytic properties of niobium(V) oxide (Nb2O5-CBMN) of different grades: amorphous, optical and ultra-pure, untreated or heat-treated at 400, 500, 700 and 900 °C were studied, before and after interaction with H2O2, by in situ Raman, FTIR-ATR and diffuse reflectance UV-Visible spectroscopy. The presence of different reaction sites for NbO7 and NbO8 type systems, which are directly related to surface defects present in different states of crystallization, were fully characterized. The reactivity of different catalysts obtained from niobium(V) oxide was investigated, using the oxidation of methyl linoleate in the presence of hydrogen peroxide as probe reaction. The reaction was followed by GC-MS, as well as by 1H and 13C NMR spectrometry and the dominant product was 9-oxo-nonanoic acid methyl ester. A reaction mechanism related to an auto-oxidation process must be occurring, leading initially to the formation of hydroperoxides, which decompose rapidly via Hock-type rearrangement, leading to the formation of aldehydes.

Superoxide radicals in the kinetics of nitroxide-inhibited oxidation of methyl linoleate in micelles

The kinetics of the oxidation of methyl linoleate in micelles inhibited by stable nitroxides under the conditions of initiation by superoxide radicals was studied. Multiple breakdown of the oxidation chains was observed in this process. The antioxidant activity of nitroxides increased when the reduction potential of the oxoammonium cation/nitroxide pair decreased and their lipophilicity increased.

Effect of superoxide dismutase on the oxidation of methyl linoleate in micelles inhibited by nitroxyl radicals

The kinetics of oxidation of methyl linoleate in micelles inhibited by stable nitroxyl radicals in the presence of superoxide dismutase was studied. In the presence of superoxide dismutase, nitroxyl radicals decrease the rate of oxidation to a lower extent and the process is characterized by lower inhibition coefficients. The results obtained demonstrate an important role of hydroperoxide radical in the mechanism of nitroxyl radical regeneration during the oxidation of methyl linoleate in micelles.

The Precise Structures and Stereochemistry of Trihydroxy-linoleates Esterified in Human and Porcine Epidermis and Their Significance in Skin Barrier Function

Creation of an intact skin water barrier, a prerequisite for life on dry land, requires the lipoxygenase-catalyzed oxidation of the essential fatty acid linoleate, which is esterified to the ω-hydroxyl of an epidermis-specific ceramide. Oxidation of the linoleate moiety by lipoxygenases is proposed to facilitate enzymatic cleavage of the ester bond, releasing free ω-hydroxyceramide for covalent binding to protein, thus forming the corneocyte lipid envelope, a key component of the epidermal barrier. Herein, we report the transformations of esterified linoleate proceed beyond the initial steps of oxidation and epoxyalcohol synthesis catalyzed by the consecutive actions of 12R-LOX and epidermal LOX3. The major end product in human and porcine epidermis is a trihydroxy derivative, formed with a specificity that implicates participation of an epoxide hydrolase in converting epoxyalcohol to triol. Of the 16 possible triols arising from hydrolysis of 9,10-epoxy-13-hydroxy-octadecenoates, using LC-MS and chiral analyses, we identify and quantify specifically 9R,10S,13R-trihydroxy-11E-octadecenoate as the single major triol esterified in porcine epidermis and the same isomer with lesser amounts of its 10R diastereomer in human epidermis. The 9R,10S,13R-triol is formed by SN2 hydrolysis of the 9R,10R-epoxy-13R-hydroxy-octadecenoate product of the LOX enzymes, a reaction specificity characteristic of epoxide hydrolase. The high polarity of triol over the primary linoleate products enhances the concept that the oxidations disrupt corneocyte membrane lipids, promoting release of free ω-hydroxyceramide for covalent binding to protein and sealing of the waterproof barrier.

Effect of microheterogeneity on the kinetics of oxidation of methyl linoleate in micelles

The kinetic results of the radical chain oxidation of methyl linoleate (LH) in micelles were given. The oxidation rate depends on the average number of substrate molecules in the micelle and is almost independent of the micelle concentration under the given conditions. The chain propagation and termination were assumed to predominantly occur inside the micelle. Possible reasons for linear chain termination during the oxidation of polyunsaturated fatty esters in microheterogeneous systems were discussed.

Antioxidative Properties of Stearoyl Ascorbate in a Food Matrix System.

Stearoyl ascorbate or 6-O-stearoyl l-ascorbate is a lipophilic derivative of l-ascorbic acid and is commercially used in foods as a fat-soluble antioxidant and surfactant to overcome the disadvantages of using l-ascorbic acid. The objective of this research is to evaluate the antioxidative ability of stearoyl ascorbate, in the presence of wheat starch or gluten as a matrix, by measuring the unoxidized methyl linoleate available in the mixture of them after oxidation under accelerated conditions compared to that when using ascorbic acid. We observed that stearoyl ascorbate and ascorbic acid exhibited mutually adjacent antioxidative ability against oxidation of the methyl linoleate at a molar ratio of 0.0001 in presence of either wheat starch or gluten. In addition, the oxidation process in the mixture containing either stearoyl ascorbate or ascorbic acid was significantly slower than that in the mixture without stearoyl ascorbate or ascorbic acid. Moreover, by altering the initiation and propagation periods of the oxidation process, the mixture containing the stearoyl ascorbate and gluten as the matrix exhibited conspicuously slower oxidation than the mixture containing either the wheat starch or stearoyl ascorbate alone. However, increase in the ratio of stearoyl ascorbate to methyl linoleate to 0.001 or higher resulted in adverse effects due to acceleration of the oxidation process.

Five-membered cyclic nitroxyl radicals as inhibitors of the oxidation of methyl linoleate in micelles

The kinetics of methyl linoleate oxidation in micelles inhibited by five-membered cyclic nitroxyl radicals and the corresponding hydroxylamines was studied. The partial regeneration of nitroxyl radicals in this process was found. The activity of the studied inhibitors increases with an increase in their lipophilicity.

Stable nitroxyl radicals and hydroxylamines as inhibitors of methyl linoleate oxidation in micelles

The kinetics of methyl linoleate oxidation in micelles inhibited by nitroxyl radicals and hydroxylamines was studied. The regeneration of nitroxyl radicals in this process was found. The activity of the studied inhibitors increases with increasing their lipophilicity. This effect was explained by increasing the distribution coefficient of the antioxidants in a micelles–water system. The reaction of nitroxyl radicals with the hydroperoxide radical formed upon the oxidation of methyl linoleate in micelles is proposed to be the key reaction in nitroxyl radical regeneration.

Maize death acids, 9-lipoxygenase-derived cyclopente(a)nones, display activity as cytotoxic phytoalexins and transcriptional mediators.

Plant damage promotes the interaction of lipoxygenases (LOXs) with fatty acids yielding 9-hydroperoxides, 13-hydroperoxides, and complex arrays of oxylipins. The action of 13-LOX on linolenic acid enables production of 12-oxo-phytodienoic acid (12-OPDA) and its downstream products, termed "jasmonates." As signals, jasmonates have related yet distinct roles in the regulation of plant resistance against insect and pathogen attack. A similar pathway involving 9-LOX activity on linolenic and linoleic acid leads to the 12-OPDA positional isomer, 10-oxo-11-phytodienoic acid (10-OPDA) and 10-oxo-11-phytoenoic acid (10-OPEA), respectively; however, physiological roles for 9-LOX cyclopentenones have remained unclear. In developing maize (Zea mays) leaves, southern leaf blight (Cochliobolus heterostrophus) infection results in dying necrotic tissue and the localized accumulation of 10-OPEA, 10-OPDA, and a series of related 14- and 12-carbon metabolites, collectively termed "death acids." 10-OPEA accumulation becomes wound inducible within fungal-infected tissues and at physiologically relevant concentrations acts as a phytoalexin by suppressing the growth of fungi and herbivores including Aspergillus flavus, Fusarium verticillioides, and Helicoverpa zea. Unlike previously established maize phytoalexins, 10-OPEA and 10-OPDA display significant phytotoxicity. Both 12-OPDA and 10-OPEA promote the transcription of defense genes encoding glutathione S transferases, cytochrome P450s, and pathogenesis-related proteins. In contrast, 10-OPEA only weakly promotes the accumulation of multiple protease inhibitor transcripts. Consistent with a role in dying tissue, 10-OPEA application promotes cysteine protease activation and cell death, which is inhibited by overexpression of the cysteine protease inhibitor maize cystatin-9. Unlike jasmonates, functions for 10-OPEA and associated death acids are consistent with specialized roles in local defense reactions.

Determination of Oxidation of Methyl Ricinoleates

AbstractRicinoleate esters have desirable properties as biolubricants, but their oxidative stability has been questioned. To systematically study the stability of ricinoleate ester and its derivative, methyl esters of castor oil were prepared and methyl ricinoleate was isolated by solvent partitioning. Methyl 12‐acetyl ricinoleate was synthesized from the methyl ricinoleate by interesterification with excess methyl acetate and was then purified by solvent partitioning. The rates of oxidation of methyl linoleate, methyl oleate and the two ricinoleate esters were measured by oxidation of lipid dispersed on glass beads under three temperatures (40–80 °C). The relative amounts of the unoxidized methyl esters were determined periodically by gas chromatography, and the peroxide value of the oils was also determined. The oxidation rates were determined as the peroxide value increase rate, as well as the ester disappearance rate, and the stability of the various esters was compared. Overall, methyl ricinoleate was much more oxidatively stable than methyl oleate at mildly elevated temperatures, and the acetylation of the hydroxyl group on the 12th carbon decreased the stability.

Effect of mercaptoethanol on the hydrocarbon oxidation and cis—trans-isomerization of unsaturated lipids

The kinetics of the oxidation of ethylbenzene, limonene, and methyl linoleate containing mercaptoethanol additives were studied, as well as cis—trans-isomerization of the double bonds in methyl linoleate. Mercaptoethanol (RSH) additives were found to accelerate the oxidation of hydrocarbons and methyl linoleate due to the reaction of RSH with hydroperoxides (primary oxidation products) resulting in a low yield of free radicals. The cis—trans-isomerization catalyzed by thiyl radicals produced in the exchange radical reactions with RSH decelerates in the presence of oxygen.

Kinetic study and simulation of methyl linoleate oxidation in micelles

The results of experiments and computer simulations on the radical-chain oxidation of methyl linoleate in micelles are reported. The reaction rate constants included in the developed mathematical model are estimated. The ratio of the rates of first-order and bimolecular chain termination is examined. It is demonstrated that the rate constant of bimolecular chain termination in micelles is lower than that in the homogeneous phase.

Extraction, antioxidative, and antimicrobial activities of brown seaweed extracts, Turbinaria ornata and Sargassum polycystum, grown in Thailand

Total phenolic content and antioxidative and antimicrobial activities of methanolic and ethanolic extracts from brown seaweeds, Turbinaria ornata and Sargassum polycystum, were determined. Among all extracts, methanolic extract of T. ornata contained the highest total phenolic content (2.07 mg catechin/g dry seaweed) (p < 0.05) and exhibited the highest antioxidative activity as indicated by the greatest ABTS and DPPH radical scavenging activity as well as reducing activity power (RAP), compared with other extracts (p < 0.05). When different concentrations of seaweed extracts (100–500 mg/L) were used, antioxidative activities were dose-dependent. Correlations between ABTS and DPPH radical scavenging activity; DPPH radical scavenging activity and RAP; ABTS radical scavenging activity and RAP were observed. Therefore, antioxidants in seaweed extracts possessed the capability of scavenging the radicals together with reducing power. The efficacy in prevention of lipid oxidation of methanolic extract of T. ornata in lecithin-liposome and linoleic oxidation systems was studied. The extract at levels of 100–500 mg/L could retard the oxidation, regardless of chlorophyll removal but its efficacy was lower than that of BHT at levels of 50 and 200 mg/L. For antimicrobial activity, all extracts could not inhibit the growth of Bacillus subtilis, Salmonella enteritidis, and Aspergillus niger, while Staphylococcus aureus was inhibited with the extracts at 500 mg/L.

Effects of various emulsification methods on the oxidation of methyl linoleate.

The effects of mechanical stress during emulsification on the oxidation of methyl linoleate were investigated by four methods (high-pressure homogenization, high-speed stirring, ultrasonic homogenization, and membrane emulsification). The oxidation rates and induction periods were almost constant, regardless of the emulsification method, except for membrane emulsification, by which the induction period was prolonged when a cellulose acetate membrane was used.

Oxidation of methyl linoleate with chemically generated singlet oxygen by the sodium molibdate/hydrogen peroxide system

Oxidation of the methyl linoleate with singlet oxygen, generated chemically by the sodium molybdate/hydrogen peroxide system (Na2 MoO4 /H2 O2 ), was studied in a type microemulsion micelle inverted (O/W). The monitoring of methyl linoleate oxidation with singlet oxygen was carried out using a UVVis spectrocopy, measuring the absorbance at 234 nm corresponding to the conjugated hydroperoxides. Under room temperature and pressure, products of the decomposition of possible dioxetane were not identified by HPLC and GC-MS, as some studies have suggested.

Antioxidant activity of brown alga Saccharina bongardiana from Kamchatka (Pacific coast of Russia). A methodological approach

The present study aims to investigate the levels of polyphenols and antioxidant activity in one of the most important commercial species of seaweeds in Kamchatka, an edible brown seaweed Saccharina bongardiana. Six extracts of S. bongardiana, acetone, methanol, ethanol, and the respective 70 % aqueous solutions, were assessed for total phenol content in order to determine the most efficient extracting solvent. The total phenol content was measured by the Folin–Ciocalteu method and expressed as phloroglucinol equivalents (PGE). The antioxidant tests used were 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, linoleic acid-β carotene oxidation inhibiting assay, and Fe2+ ion chelating method. Higher phenolic contents were obtained using aqueous organic solvents, as compared to the respective absolute solvents; 70 % acetone was found to be the most efficient solvent (1.039 mg PGE 100 mg−1 dry algal powder). High significant correlations were noted between total phenol content and the tested antioxidant activities; so the aqueous organic extracts exhibited the highest antioxidant activities versus DPPH radicals (EC50 values of 0.6–1.1 mg dry weight (DW) mL−1), linoleic acid-β carotene oxidation (74–78 % at 0.8 mg DW mL−1), as well as ferrous ions (EC50 values of 5.0–7.9 mg DW mL−1). Some methodological recommendations regarding the assays used and the expression of results are proposed.

Reactivity toward oxygen radicals and antioxidant action of thiol compounds

Thiol compounds exert diverse functions in the defense network against oxidative stress in vivo. Above all, the role of glutathione in the enzymatic removal of hydrogen peroxide and lipid hydroperoxides has been well established. The scavenging of reactive free radicals is one of the many functions. In this study, the reactivities of several thiol compounds toward oxygen- and nitrogen-centered radicals were measured from their reaction with galvinoxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and also from their sparing effects on the decay of fluorescein, pyrogallol red, and BODIPY induced by peroxyl radicals. Furthermore, the antioxidant capacity against lipid peroxidation was assessed in the oxidation of methyl linoleate induced by free radicals in micelle systems. Cysteine, homocysteine, and glutathione exhibited considerable reactivity toward galvinoxyl, DPPH, and peroxyl radicals in this order but methionine did not. Bovine serum albumin (BSA) was less reactive toward these radicals than cysteine on molar base. Cysteine, homocysteine, and glutathione suppressed the oxidation of methyl linoleate in micelle systems, but methionine did not. The reactivity toward free radicals and antioxidant capacity of these thiol compounds were less than that of ascorbic acid, but higher than that of uric acid.

Antioxidant anti-inflammatory activity of Alstonia scholaris R.Br. stem bark extract

Background: The plant Alstonia scholaris R.Br. (Labiatae) is widely cultivated throughout India. The bark of this tree is medicinally used as an astringent, tonic, anthelmintic, antiperiodic and febrifuge. Methods: The effect of Methanolic extract of stem bark of Alstonia scholaris R.Br. was investigated to evaluate the antioxidant activity by TLC method and anti-inflammatory activity by Carrageenan induced rat paw odema, dextran induced rat paw odema and cotton pellet induced granuloma. Result: Anti-inflammatory activity of the tested extract and its fractions was comparable with that of the standard drug Indomethacin (10 mg/kg). Conclusion: The present investigation for the first time, confirms the potential anti-inflammatory activity in the methanol extract of Alstonia scholaris stem bark. Antioxidant property of the extract was confirmed quantitatively by β-carotene–linoleate oxidation method by thin layer chromatography.

Oxidation of Methyl Linoleate Mixed with Methyl Octanoate, Laurate or Palmitate

Oxidation of Methyl Linoleate Mixed with Methyl Octanoate, Laurate or Palmitate