Relationship between the action of reactive oxygen and nitrogen species on bilayer membranes and antioxidants

Spirulina sp. LEB 18-extracted phycocyanin: Effects on liposomes' physicochemical parameters and correlation with antiradical/antioxidant properties

This study describes the physicochemical properties of soybean asolectin (ASO) liposomes loaded with phycocyanin (Phy) extracted from Spirulina sp. LEB 18. The effects of Phy in the liposomes' properties were investigated by Fourier transform infrared spectroscopy (FTIR), ¹H and ³¹P nuclear magnetic resonance (NMR), zeta (ζ)-potential, dynamic light scattering (DLS) and ultraviolet-visible (UV-vis) techniques. Phy restricted the motion of ASO polar and interface groups and disrupted the package arrangement of the lipid hydrophobic regions, as a likely effect of dipolar and π interactions related to its amino acid residues and pyrrole portions. These interactions were correlated to antiradical/antioxidant Phy responses obtained by 2,2-diphenyl-1-picrylhidrazil (DPPH) assay, thiobarbituric acid reactive substances (TBARS) and ferric reducing antioxidant power (FRAP) methods, and discussed to bring new chemical perspectives about Phy-loaded liposomes-related nutraceutical applications in inflammatory and viral infection processes.

The gravity dependence of pharmacodynamics: the integration of lidocaine into membranes in microgravity

To realize long-term manned space missions, e.g. to Mars, some important questions about pharmacology under conditions of different gravity will have to be answered to ensure safe usage of pharmaceuticals. Experiments on the International Space Station showed that the pharmacokinetics of drugs are changed in microgravity. On Earth, it is well known that the incorporation of substances into cellular membranes depends on membrane fluidity, therefore the finding that membrane fluidity is gravity dependent possibly has effects on pharmacodynamics of hydrophobic and amphiphilic substances in microgravity. To validate a possible effect of gravity on pharmacodynamics, experiments have been carried out to investigate the incorporation of lidocaine into plain lipid membranes under microgravity conditions. In microgravity, the induced increase in membrane fluidity associated with lidocaine incorporation is smaller compared to 1g controls. This experiment concerning the gravity dependence of pharmacodynamics in real microgravity clearly shows that the incorporation of amphipathic drugs into membranes is changed in microgravity. This might have significant impact on the pharmacology of drugs during long-term space missions and has to be investigated in more detail to be able to assess possible risks.

A role for Sel-Plex™, a source of organic selenium in selenised yeast cell wall protein, as a factor that influences meat stability

Selenium is an important mineral required in the antioxidant system in animals, which is involved with oxidative stability in tissues, particularly membranes, and is involved in various aspects of meat quality and stability on the shelf, due to its protective properties on lipids, preventing rancidity. Se can be supplied in an inorganic or chemically organic form, and it is well known that the latter has beneficial properties and improved functionality in physiological systems compared to the former. Research has shown that organic Se is associated with increased tenderness and the prevention of certain problems in pale exudative meat, discolouration and off-flavours and odours in meat, although this depends on other components of the antioxidant system, such as vitamin E, being present as well. The change in prominence of glutathione peroxidase forms in their interaction with vitamin E in cell membranes is also noted. The following review (the third in a series) details the research that has been conducted into the role of Se in meat stability and related factors, with specific focus on organic forms of Se, namely the commercial product Sel-Plex™ (Alltech Inc, Nicholasville, KY, USA), which is derived from yeast and in which selenium replaces sulphur in methionine forming selenomethionine in yeast protein.

Organic selenium in animal nutrition – utilisation, metabolism, storage and comparison with other selenium sources

The importance of selenium as a key component of antioxidant systems in animals is well recognised due to much research about this mineral in many species. Selenium is required as part of the antioxidant enzyme structure and plays a major role in various protective systems in animal physiology, including immunity, cellular stability and DNA protection. The following review is the first in a series of three which details the importance of selenium in animal nutrition, and how the chemically organic form, which is akin to the form of the mineral in natural feed materials, can provide increased benefits in utilisation, storage and metabolism compared to inorganic sources.

Effects of high CO₂ levels on fermentation, peroxidation, and cellular water stress in Fragaria vesca stored at low temperature in conditions of unlimited O₂

To better understand the tolerance of strawberries (Fragaria vesca L.) to high CO2 in storage atmospheres, fermentation and cellular damage were investigated. Fruits were stored for 3 and 6 days at 0 °C in the presence of different CO2 levels (0, 20, or 40%) with 20% O2. Changes in pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) gene expression and in fermentative metabolites, as well as in bound water and malondialdehyde (MDA) concentrations, were analyzed. In strawberries stored without added CO2, up-regulation of PDC and ADH was not associated with an increase in fermentative metabolites. By contrast, moderate ethanol fermentation in fruits exposed to 20% CO2 seems to be essential to maintain fruit metabolism, reducing both lipid peroxidation and cellular water stress. However, if the CO2 concentration increases (40%), the excess acetaldehyde and ethanol produced were closely correlated with a decrease in bound water and production of MDA.

Effects of α-eleostearic acid on asolectin liposomes dynamics: relevance to its antioxidant activity

In this study, the effect of α-eleostearic acid (α-ESA) on the lipid peroxidation of soybean asolectin (ASO) liposomes was investigated. This effect was correlated to changes caused by the fatty acid in the membrane dynamics. The influence of α-ESA on the dynamic properties of liposomes, such as hydration, mobility and order, were followed by horizontal attenuated total reflection Fourier transform infrared spectroscopy (HATR-FTIR), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and UV-vis techniques. The α-ESA showed an in vitro antioxidant activity against the damage induced by hydroxyl radical (OH) in ASO liposomes. The analysis of HATR-FTIR frequency shifts and bandwidths and (1)H NMR spin-lattice relaxation times, related to specific lipid groups, showed that α-ESA causes an ordering effect on the polar and interfacial regions of ASO liposomes, which may restrict the OH diffusion in the membrane. The DSC enthalpy variation analysis suggested that the fatty acid promoted a disordering effect on lipid hydrophobic regions, which may facilitate interactions between the reactive specie and α-ESA. Turbidity results showed that α-ESA induces a global disordering effect on ASO liposomes, which may be attributed to a change in the lipid geometry and shape. Results of this study may allow a more complete view of α-ESA antioxidant mode of action against OH, considering its influence on the membrane dynamics.

Vitamin (B1, B2, B3 and B6) content and oxidative stability of Gastrocnemius muscle from dry-cured hams elaborated with different nitrifying salt contents and by two ageing times

The effect of the amount of added nitrate and nitrate plus nitrite to dry-cured hams on the vitamin (B1, B2, B3, B6) content, the antioxidant enzyme superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx) activities and the thiobarbituric acid reactive substances (TBARS) was assessed in Gastrocnemius muscle at the end of two ripening processes. Five different curing mixtures (Hi-N: 600 KNO3; Lo-N: 150 KNO3; Hi-Mix: 600 KNO3+600 NaNO2; Lo-Mix: 150 KNO3+150 NaNO2; Hi-Mix/Asc: 600 KNO3+600 NaNO2+500 sodium ascorbate, expressed as mg of salts added on surface per kg of fresh ham) were evaluated in dry-cured hams aged for 11.5months (standard process, SP) and 22months (long process, LP). Minor differences in target parameters between the hams due to the process were found. The amount of nitrate when it was added alone or as a mixture of nitrate and nitrite, as well as the ascorbate addition to dry-cured hams did not affect vitamin B1, B2 and B3 contents. The level of vitamin B6 was affected by both the amount and the mixture of salts; the addition of nitrite reduced around 40% the content of vitamin B6, but it was not affected by nitrate or ascorbate. The activity of SOD and CAT decreased with the amount of nitrate and nitrite, while GSHPx and TBARS resulted unaffected.

Response surface optimized ultrasonic-assisted extraction of flavonoids from Sparganii rhizoma and evaluation of their in vitro antioxidant activities

An efficient ultrasound-assisted extraction technique was employed to extract total flavonoids from Sparganii rhizoma. The optimum extraction conditions for the highest yield of total flavonoids were ethanol concentration 53.62%, ultrasonication time 29.41 min and ultrasound power 300 W, which were determined using response surface methodology. The extraction yields of the optimal ultrasound-assisted extraction were higher than using conventional extraction. The crude extract was then purified on a polyamide resin, whereby the flavonoids content in the purified extract increased to 94.62%. The antioxidant activities of the purified flavonoids including DPPH radical scavenging activity, ABTS+ radical scavenging activity, reducing power, hydroxyl radical scavenging activity and superoxide anion scavenging activity, were evaluated in vitro, which suggested that the flavonoids showed significant antioxidant activities. Rutin, kaempferol and formononetin were identified in the extract by comparing relative retention times and UV-Vis spectra with those of reference standards.

The natural antioxidant rosmarinic acid spontaneously penetrates membranes to inhibit lipid peroxidation in situ

Exogenous molecules from dietary sources such as polyphenols are very efficient in preventing the alteration of lipid membranes by oxidative stress. Among the polyphenols, we have chosen to study rosmarinic acid (RA). We investigated the efficiency of RA in preventing lipid peroxidation and in interacting with lipids. We used liposomes of 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC) to show that RA was an efficient antioxidant. By HPLC, we determined that the maximum amount of RA associated with the lipids was ~1 mol%. Moreover, by using Langmuir monolayers, we evidenced that cholesterol decreases the penetration of RA. The investigation of transferred lipid/RA monolayers by atomic force microscopy revealed that 1 mol% of RA in the membrane was not sufficient to alter the membrane structure at the nanoscale. By fluorescence, we observed no significant modification of membrane permeability and fluidity caused by the interaction with RA. We also deduced that RA molecules were mainly located among the polar headgroups of the lipids. Finally, we prepared DLPC/RA vesicles to evidence for the first time that up to 1 mol% of RA inserts spontaneously in the membrane, which is high enough to fully prevent lipid peroxidation without any noticeable alteration of the membrane structure due to RA insertion.

In vitro antioxidant properties and phenolic composition of Salvia halophila Hedge from Turkey

An endemic plant of Turkey Salvia halophila Hedge (Lamiaceae) was examined for its antioxidant activity and phenolic compositions. The aerial part of S. halophila was extracted with different solvents in an order of increasing polarity such as hexane, ethyl acetate, methanol, and 50% methanol using a Soxhlet apparatus. Water extract was also prepared from S. halophila by reflux. All solvent fractions were investigated for their total phenolic contents, flavonoids, flavonols, qualitative-quantitative compositions, iron(III) reductive activities, free radical scavenging activities and the effect upon linoleic acid peroxidation activities. The peroxidation level was also determined by the TBA method. The results of activity tests given as IC₅₀ values were estimated from non-linear algorithm and compared with standards via BHT, ascorbic acid, gallic acid. Polar fractions were found more active among the others in free radical activity system whereas non-polar fractions protected the peroxidation of linoleic acid. Rosmarinic acid was the most abundant component, in the extracts.

Peroxynitrite affects lidocaine by acting on membrane-constituting lipids

Inflammation frequently decreases local anesthetic effects, especially in dental anesthesia in patients with pulpitis and periodontitis. The pharmacokinetics and the mode of action of local anesthetics are closely associated with the hydrophobic interactions between these drugs and lipid bilayers that change the membrane physicochemical property, fluidity. A lipid oxidant, peroxynitrite, is produced by inflammatory cells, and it may act on nerve cell membranes and affect anesthetic efficacy. With respect to this speculated action, we addressed whether peroxynitrite acted on membrane-constituting lipids to decrease the membrane interactivity of lidocaine. Membrane fluidity changes were determined by measuring the fluorescence polarization of liposomes prepared with different phospholipids. Peroxynitrite (0.1-50 microM) rigidified nerve-cell model membranes consisting of unsaturated phospholipids, as well as liposomal membranes consisting of 1,2-dioleoylphosphatidylcholine and 1-stearoyl-2-arachidonylphosphatidylcholine, but peroxynitrite did not rigidify 1, 2-dipalmitoylphosphatidylcholine liposomal membranes. The pretreatment of nerve-cell model membranes with peroxynitrite (0.1-50 microM) decreased the membrane-fluidizing effects of lidocaine (5.0 mg x ml(-1)) to 63%-86% of the control (not treated with peroxynitrite) depending on the peroxynitrite concentration. As one of the mechanisms of the local anesthetic failure associated with inflammation, inflammatory peroxynitrite may affect local anesthesia by acting on membrane-constituting unsaturated phospholipids.

Melatonin location in egg phosphatidylcholine liposomes: possible relation to its antioxidant mechanisms

Although it is known that the antioxidant properties of melatonin can be modulated by its effect on membrane fluidity, there are few studies on this subject reported in the literature and they are controversial. In this study, viscosimetry and nuclear magnetic resonance (NMR) techniques were used to determine melatonin's effect and location on egg phosphatidylcholine bilayers mobility. Melatonin decreases the dynamic viscosity of the lipid dispersion. (31)P-NMR line width analysis indicated that melatonin induces a slight but uniform restriction of the lipid motional freedom in the polar head. However, melatonin changes in choline (13)C dynamics was only observed through chemical shift analysis. On the other hand, melatonin can induce an increase in the lipid nonpolar chain mobility, as observed by (13)C and (1)H relaxation time analysis. These results suggest the interfacial location of melatonin in the membrane. Additionally, the results of the analysis of the lipid (1)H-fitted exponential relaxation times suggest that melatonin promotes a molecular rearrangement of the bilayers. The melatonin effect and location in the lipid membrane may explain its antioxidant properties against lipid peroxidation induced by reactive species.

Antioxidant properties of violacein: Possible relation on its biological function

Violacein, a violet pigment produced by Chromobacterium violaceum, has attracted much attention in recent literature due to its pharmacological properties. In this work, the antioxidant properties of violacein were investigated. The reactivity with oxygen and nitrogen reactive species and 1,1-diphenyl-2-picryl-hydrazyl (DPPH), a stable free radical, was evaluated. EPR studies were carried out to evaluate the reactivity with the hydroxyl radical. The action of violacein against lipid peroxidation in three models of lipid membranes, including rat liver microsomes, Egg and Soy bean phosphathidylcholine liposomes were also evaluated. The compound reacted with DPPH (IC(50)=30microM), nitric oxide (IC(50)=21microM), superoxide radicals (IC(50)=125microM) and decreased the hydroxyl radical EPR signal. The compound protected the studied membranes against peroxidation induced by reactive species in the micromolar range. The reconstitution of violacein into the membranes increased its antioxidant effect. These results indicate that the compound has strong antioxidant potential. Based on these results we suggest violacein plays an important role with the microorganism membrane in defense against oxidative stress.