Characterization of the antioxidant activity of sugars and polyhydric alcohols in fish oil emulsions

Polyols have been incorporated into fish oil emulsions as a means for the inhibition of lipid oxidation and suppression of fishy flavor. However, the role of sugars and polyhydric alcohols as antioxidants has not been clearly established. Selected polyols were evaluated for their performance as antioxidants and modifiers of oxidation pathways in a model system. Oil/water (O/W) emulsions were prepared with freshly steam-deodorized menhaden oil. A layer of emulsion in aluminum pans held at 5 degrees C was exposed to 2550 lx fluorescent lights for 24 h before peroxide values and volatile flavor compounds were analyzed by GC headspace entrainment procedure. Antioxidant activity was confirmed for fructose, sucrose, raffinose, sorbitol, or mannitol when incorporated at 16% of the aqueous phase into model fish oil-in-water emulsions. Peroxide values were suppressed 10-18% in treated samples compared to control samples. Viscosity data did not exclude possible contributions from a restricted oxygen diffusion mechanism in the antioxidant activity, but revealed that emulsion viscosity did not govern fish oil oxidation rates. Combining polyols with phenolic antioxidants (alpha-tocopherol, BHT, or TBHQ) frequently diminished the antioxidant activity compared to that for individual phenolic antioxidants, which was interpreted as indicating that the H-donating activity of phenolic antioxidants was hindered by the H-bonding activity of polyols. A viscosity-based inhibition of the retroaldol conversion of (E,Z)-2,6-nonadienal to (Z)-4-heptenal with a high fructose concentration (67%) was attributed to a restriction of molecular mobility of reactants, but the conversion was only slightly inhibited by the concentration of fructose (16%) used in experimental emulsions. The data supported a hypothesis that either or both free radical scavenging and transition state metal chelation activities were provided by polyols in fish oil emulsions. Also, polyols retarded the water-requiring retroaldol decomposition of (E,Z)-2,6-nonadienal to (Z)-4-heptenal in the model systems and the reaction may be involved in some suppression of fishy flavors in emulsions.     

Antioxidant activity of oregano, parsley, and olive mill wastewaters in bulk oils and oil-in-water emulsions enriched in fish oil

The antioxidant activity of oregano, parsley, olive mill wastewaters (OMWW), Trolox, and ethylenediaminetetraacetic acid (EDTA) was evaluated in bulk oils and oil-in-water (o/w) emulsions enriched with 5% tuna oil by monitoring the formation of hydroperoxides, hexanal, and t-t-2,4-heptadienal in samples stored at 37 degrees C for 14 days. In bulk oil, the order of antioxidant activity was, in decreasing order (p < 0.05), OMWW > oregano > parsley > EDTA > Trolox. The antioxidant activity in o/w emulsion followed the same order except that EDTA was as efficient an antioxidant as OMWW. In addition, the total phenolic content, the radical scavenging properties, the reducing capacity, and the iron chelating activity of OMWW, parsley, and oregano extracts were determined by the Folin-Ciocalteau, oxygen radical absorbance capacity, ferric reducing antioxidant power, and iron(II) chelating activity assays, respectively. The antioxidant activity of OMWW, parsley, and oregano in food systems was related to their total phenolic content and radical scavenging capacity but not to their ability to chelate iron in vitro. OMWW was identified as a promising source of antioxidants to retard lipid oxidation in fish oil-enriched food products.     

Oxidative stability of fish and algae oils containing long-chain polyunsaturated fatty acids in bulk and in oil-in-water emulsions

The oxidative stability of long-chain polyunsaturated fatty acid (PUFA) and docosahexaenoic acid (DHA)-containing fish and algae oils varies widely according to their fatty acid composition, the physical and colloidal states of the lipids, the contents of tocopherols and other antioxidants, and the presence and activity of transition metals. Fish and algal oils were initially much more stable to oxidation in bulk systems than in the corresponding oil-in-water emulsions. The oxidative stability of emulsions cannot, therefore, be predicted on the basis of stability data obtained with bulk long-chain PUFA-containing fish oils and DHA-containing algal oils. The relatively high oxidative stability of an algal oil containing 42% DHA was completely lost after chromatographic purification to remove tocopherols and other antioxidants. Therefore, this evidence does not support the claim that DHA-rich oils from algae are unusually stable to oxidation. Addition of ethylenediaminetetraacetic acid (EDTA) prevented oxidation of both fish and algal oil emulsions without added iron and at low iron:EDTA molar concentrations. EDTA, however, promoted the oxidation of the corresponding emulsions that contained high iron:EDTA ratios. Therefore, to be effective as a metal chelator, EDTA must be added at molar concentrations higher than that of iron to inhibit oxidation of foods containing long-chain PUFA from either fish or algae and fortified with iron.     

Antioxidant activities and volatile constituents of various essential oils

Thirteen essential oils were examined for their antioxidant activity using three different assay systems. Jasmine, parsley seed, rose, and ylang-ylang oils inhibited hexanal oxidation by over 95% after 40 days at a level of 500 microg/mL in the aldehyde/carboxylic acid assay. Scavenging abilities of the oils for the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical ranged from 39% for angelica seed oil to 90% for jasmine oil at a level of 200 microg/mL. The greatest inhibitory activity toward malonaldehyde (MA) formation from squalene upon UV-irradiation was obtained from parsley seed oil (inhibitory effect, 67%), followed by rose oil (46%), and celery seed oil (23%) at the level of 500 microg/mL. The main compounds of oils showing high antioxidant activity were limonene (composition, 74.6%) in celery seed, benzyl acetate (22.9%) in jasmine, alpha-pinene (33.7%) in juniper berry, myristicin (44%) in parsley seed, patchouli alcohol (28.8%) in patchouli, citronellol (34.2%) in rose, and germacrene (19.1%) in ylang-ylang.     

Activities of antioxidants are affected by colloidal properties of oil-in-water and water-in-oil emulsions and bulk oils

The activity of alpha-tocopherol, Trolox, propyl gallate, gallic acid, methyl carnosoate, and carnosic acid was studied in two oil-in-water (o/w) emulsions, in two water-in-oil (w/o) emulsions, and in bulk oil with and without added emulsifiers. All antioxidants had either moderate or higher activity in bulk oil than in the emulsions. In most emulsions, the most polar antioxidants, propyl gallate and gallic acid, exhibited either prooxidant activity or no antioxidant activity. Methyl carnosoate was the most active antioxidant in w/o emulsions but was less active than Trolox in o/w emulsions. alpha-Tocopherol was less active in bulk oil than in emulsions, but its activity in bulk oil was markedly enhanced by the addition of o/w emulsifiers. Partitioning of antioxidants, hydrogen bonding, interphase transport, surface accessibility, and interaction of emulsifier with antioxidants are considered to be important parameters that determine antioxidant activity in lipid-containing systems.     

High-throughput quantitation of peroxyl radical scavenging capacity in bulk oils

Autoxidation of methyl linoleate (8:2 mixture with decane, 37 degrees C) was induced by 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN, 17.7 mM) and the kinetics of oxygen consumption monitored using a 96-well microplate coated with an oxygen-sensitive fluorescence probe, a ruthenium dye, embedded in a silicone matrix at the bottom of the microplate. The probe does not participate in the reaction; instead, its fluorescence intensity is inversely proportional to the solution oxygen concentration as it changes during oxidation. In the absence of antioxidants, the oxidation rate has a linear relationship with the square root of the initiator concentrations. This is in agreement with theoretical autoxidation kinetics equations. In the presence of tocopherol-type antioxidants, a sharp lag phase appears. The quantitation of the antioxidant capacity is achieved using the area under the curve (AUC) approach. The assay has a 2 h running time, a linearity range from 1.56 to 18.7 microM (Trolox), and a limit of quantitation at 2.7 microM Trolox equivalency. The peroxyl radical scavenging capacities of several cold-pressed and organically grown plant seed oils were quantified along with the tocopherol concentrations of the oils. Tocopherols contribute only a fraction of the peroxyl radical scavenging capacity of the oils, and there is poor correlation between total tocopherol concentrations and radical scavenging capacity, suggesting that the antioxidant capacity of oils is due not only to tocopherols but also to other lipid-soluble antioxidants.     

Antioxidant protection of resveratrol and catechin in Saccharomyces cerevisiae

Moderate consumption of red wine reduces the risk of heart disease and extends lifespan, but the relative contribution of wine polyphenols to these effects is unclear. In this work, the capacity of resveratrol and catechin to protect the eukaryotic microorganism Saccharomyces cerevisiae against oxidative stress caused by different agents, hydrogen peroxide, carbon tetrachloride, and cadmium, was evaluated. Under all stress conditions, both polyphenols increased tolerance, although their protection was more evident under peroxide exposure. By using mutant strains deficient in specific antioxidant defense systems (superoxide dismutases, catalase, or glutathione), it was observed that increased H2O2 tolerance produced by both polyphenols was associated with catalase, as well as the rise in survival rates caused by resveratrol under CCl4. The acquisition of tolerance was correlated with a reduction in lipid peroxidation, indicating that the antioxidant property of resveratrol and catechin involves protection against membrane oxidation.     

Antioxidant behavior in bulk oil: limitations of polar paradox theory

The polar paradox theory that explains the efficacy of antioxidants as affected by their polarity and that of the medium involved was re-evaluated. For the first time, the effect of concentration on validity of the polar paradox theory was investigated using four pairs of polar and nonpolar representative antioxidants in bulk oil. A model on antioxidant behavior in response to their polarity is proposed.     

Authentication of vegetable oils by bulk and molecular carbon isotope analyses with emphasis on olive oil and pumpkin seed oil

The authenticity of vegetable oils consumed in Slovenia and Croatia was investigated by carbon isotope analysis of the individual fatty acids by the use of gas chromatography-combustion-isotope ratio mass spectrometry (GC/C/IRMS), and through carbon isotope analysis of the bulk oil. The fatty acids from samples of olive, pumpkin, sunflower, maize, rape, soybean, and sesame oils were separated by alkaline hydrolysis and derivatized to methyl esters for chemical characterization by capillary gas chromatography/mass spectrometry (GC/MS) prior to isotopic analysis. Enrichment in heavy carbon isotope ((13)C) of the bulk oil and of the individual fatty acids are related to (1) a thermally induced degradation during processing (deodorization, steam washing, or bleaching), (2) hydrolytic rancidity (lipolysis) and oxidative rancidity of the vegetable oils during storage, and (3) the potential blend with refined oil or other vegetable oils. The impurity or admixture of different oils may be assessed from the delta(13)C(16:0) vs. delta(13)C(18:1) covariations. The fatty acid compositions of Slovenian and Croatian olive oils are compared with those from the most important Mediterranean producer countries (Spain, Italy, Greece, and France).     

Antioxidant activity and partitioning of phenolic acids in bulk and emulsified methyl linoleate.

To evaluate the effect of colloidal parameters on the activity of natural antioxidants, the effect of selected phenolic acids on both bulk and emulsified methyl linoleate oxidation (in the dark at 40 degrees C) was examined. Oxidation was monitored by determining the formation of hydroperoxides; their isomer distribution and ketodiene (oxodiene) products were monitored by using high-performance liquid chromatography. This study showed the system- and concentration-dependent antioxidant activity of phenolic acids. The scavenging of alpha,alpha-diphenyl-beta-picrazylhydrazyl radicals reflected the antioxidant activity in a bulk oil system but not in an emulsion. Specific interactions of the antioxidant with other compounds, for example, the emulsifier, and intramolecular hydrogen bonds may play an important role in reducing the antioxidant activity. Furthermore, these interactions of antioxidants with emulsifier have a strong influence on the partitioning of antioxidants. Thus, the proportion of the antioxidant solubilized in the lipid phase and particularly in the interface did not necessarily reflect the efficiency of the antioxidant.     

Determination of esters of fatty acids with low molecular weight alcohols in olive oils

A simple and precise analytical method was developed for the simultaneous determination of squalene and methyl, ethyl, propyl, and butyl esters of fatty acids present in olive and olive pomace oils. A fraction containing squalene and fatty acid alkyl esters was isolated from the oil by solid phase extraction on silica gel cartridges and quantitatively analyzed by gas chromatography. A modification of the procedure allowed the isolation of squalene and esters separately. Repeatability and recovery of the method were good. The method was applied to extra and lampant virgin olive oil categories and also to oils obtained from olive pomace by second centrifugation and solvent extraction. Extra virgin olive oils contained low amounts of fatty acid methyl and ethyl esters, while oils obtained from altered olive or olive pomace showed high concentrations of fatty acid alkyl esters, mainly ethyl esters. Correlation between oil acidity and ethyl esters concentration was poor.     

Antioxidant activity of 3-dehydroshikimic acid in liposomes,emulsions, and bulk oil

The antioxidant activity of 3-dehydroshikimic acid (DHS), an intermediate in the biosynthesis of aromatic amino acids, was evaluated in three assay systems: bulk oil (lard), liposomes, and a 10% corn oil-in-water emulsion. Upon initiation of peroxidation in the liposome or emulsion systems, DHS exhibited weak antioxidant activity. In contrast, DHS displayed strong antioxidant activity in lard, suppressing peroxidation with activity comparable to that of tert-butylhydroquinone, propyl gallate, and gallic acid and superior to that of alpha-tocopherol. Two major DHS oxidation products, gallic acid and protocatechuic acid, were identified by gas chromatography/mass spectral analysis of lard extracts; both compounds are effective antioxidants in the bulk oil system. In the liposome system, DHS remained intact throughout the assay period. A small amount of gallic acid was observed in extracts of the emulsion; however, protocatechuic acid was not detected. A mechanism to explain the different activities of DHS in the three lipid systems is proposed.     

High-yield preparation of wax esters via lipase-catalyzed esterification using fatty acids and alcohols from crambe and camelina oils

Fatty acids obtained from seed oils of crambe (Crambe abyssinica) and camelina (Camelina sativa) via alkaline saponification or steam splitting were esterified using lipases as biocatalysts with oleyl alcohol and the alcohols derived from crambe and camelina oils via hydrogenolysis of their methyl esters. Long-chain wax esters were thus obtained in high yields when Novozym 435 (immobilized lipase B from Candida antarctica) and papaya (Carica papaya) latex lipase were used as biocatalysts and vacuum was applied to remove the water formed. The highest conversions to wax esters were obtained with Novozym 435 (> or =95%) after 4-6 h of reaction, whereas with papaya latex lipase such a high degree of conversion was attained after 24 h. Products obtained from stoichiometric amounts of substrates were almost exclusively (>95%) composed of wax esters having compositions approaching that of jojoba (Simmondsia chinensis) oil, especially when crambe fatty acids in combination with camelina alcohols or camelina fatty acids in combination with crambe alcohols were used as substrates.     

Antioxidant activity and soluble sugars of African ginger (Siphonochilus aethiopicus) in response to irrigation regimen and nitrogen levels

African ginger (Siphonochilus aethiopicus), as a medicinal plant, is known for its medicinal properties, containing various antioxidant compounds and carbohydrates. Rhizome yield is improved by water regimens and fertilizers applied at plant phenological stages. However, the rhizomatous herb, which is traditionally used for the treatment of asthma, inflammation and malaria has limited information on water and nitrogen requirements for its production. This study assessed the effect of irrigation regimens (30%, 50% and 70% allowable depletion level (ADL) and nitrogen (N) levels (0, 50, 100, 150 and 200?kg?ha^?1) on antioxidant activity and carbohydrates on plant leaf, root and rhizome. The interaction treatment effect of severely stressed (70% ADL) with the N application of 100?kg?ha^?1 had significant effect on leaf phenolic concentration (87.02?±?2.51?mg?g^?1 gallic acid equivalent). Interaction effect of moderately stressed (50% ADL) and severely stressed (70% ADL) treatment with N application rate of 0?kg?ha^?1 had significant effect on plant flavonoids and phenolics in all plant parts. In plant carbohydrates, root had high sucrose content (47.68?±?9.0?mg?g^?1 dry weight) with the application of low N (0?kg?ha^?1) grown under severely stressed treatment. In conclusion, this implies that different S. aethiopicus parts can produce substantial amount of antioxidants and carbohydrates, as exhibited under low N and reduced water supply applied during the phenological cycle.     

Antioxidant effect of two virgin olive oils depends on the concentration and composition of minor polar compounds

In vitro studies show that some individual minor polar phenolic compounds (MPC) present in virgin olive oil prevent oxidation of human low-density lipoproteins (LDL), but few data are available on the antioxidant effect of whole oil extract. Thus, whole virgin olive extracts were studied to determine whether they maintain the antioxidant activity and whether this last is linked to MPC composition of a single virgin oil. Using HPLC-DAD the MPC content in Taggiasca and Seggianese virgin olive oils was measured. Taggiasca oil was less rich in total MPC (208.5 mg/L) than Seggianese oil (441.9 mg/L). In addition, the major compounds of Taggiasca oil were lignan derivatives, whereas the major compounds in Seggianese oils were secoiridoid derivatives. Moreover, Taggiasca oil was practically free of 5-hydroxytyrosol and 5-hydroxytyrosol derivatives, deacetoxy-oleuropein aglycone and oleuropein aglycone. The antioxidant activity of the oils on human LDL was evaluated by measuring malondialdehyde and conjugate diene generation induced by copper ions. In both tests, the oil extracts dose-dependently reduced malondialdehyde and conjugate diene generation. Moreover, antioxidant potency correlated with total MPC; thus, Seggianese extract was more active. The two oils differed quantitatively and qualitatively, and these differences influenced their biological activities; thus clinical trials focused on studying the effects of olive oils should specify the oils used.     

Fluorescence of raw cane sugars evaluated by chemometrics

In a fluorescence study of raw cane sugar samples, two-way and three-way chemometric methods have been used to extract information about the individual fluorophores in the sugar from fluorescence excitation-emission landscapes. A sample set of 47 raw sugar samples representing a varied selection was analyzed, and three individual fluorophores with (275, 350) nm, (340, 420) nm, and (390, 460) nm as their approximate excitation and emission maxima were found. The spectral profiles of the fluorophores were estimated with the three-way decomposition model PARAFAC. Two-way principal component analysis (PCA) of unfolded fluorescence landscapes confirmed the PARAFAC results and showed patterns of samples related to time of storage. Partial least squares (PLS) calibration models of color at 420 nm had a high model error due to the very high color range of the raw sugars, but variable selection performed on the fluorescence data revealed that all three fluorophores were correlated to color. The (275, 350) nm fluorophore is considered as a color precursor to the color developed on storage and the (340, 420) nm and (390, 460) nm fluorophores show colorant polymer characteristics.     

Effects of fishing protection on the genetic structure of fish populations

Marine reserves have been identified as an important tool in the management of fishery resources and their number is increasing rapidly, most of them being on islands. However, knowledge on the real effect of protection from fishing on the genetic structure of populations, the spatial scales involved, or the suitability of islands as reserves in terms of connectivity, is scarce. This paper analyses the effects of fishery protection on the genetic structure of populations of Diplodus sargus, a target species, in protected and non-protected areas of the western Mediterranean. Populations studied showed high genetic variability at spatial scales from 10¹ to 10³ km. Protected areas have significantly higher allelic richness. The lower levels of heterozygosis and higher heterozygote deficit showed by islands compared with coastal areas makes clear the importance of considering the connectivity processes when designing a MPA.     

Antioxidant properties of a radical-scavenging peptide purified from enzymatically prepared fish skin gelatin hydrolysate

Hoki (Johnius belengerii) skin gelatin was hydrolyzed with three commercial enzymes to identify radical-scavenging potencies of derived peptides. Peptides derived from tryptic hydrolysate exhibited the highest scavenging activities on superoxide, carbon-centered 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals assessed by ESR spectroscopy. Following consecutive chromatographic separations of tryptic hydroolysate, the peptide sequence His-Gly-Pro-Leu-Gly-Pro-Leu (797 Da) acted as a strong radical scavenger under studied conditions. Further, this peptide could act as an antioxidant against linoleic acid peroxidation and the activity was closer to the highly active synthetic antioxidant butylated hydroxytoluene (BHT). In addition, antioxidative enzyme levels in cultured human hepatoma cells were increased in the presence of this peptide and it was presumed to be the peptide involved in maintaining the redox balance in the cell environment. Present data indicate that free-radical-scavenging activities of hoki skin gelatin peptides substantially contribute to their antioxidant properties measured in different oxidative systems.     

Effect of cultivar on the protection of cardiomyocytes from oxidative stress by essential oils and aqueous extracts of basil (Ocimum basilicum L.)

Notwithstanding the wide range of biological and pharmacological activities reported for sweet basil (Ocimum basilicum L.), many discrepancies are still present in the evaluation of its health-promoting properties. These discordances could be at least in part due to insufficient details of qualitative and quantitative composition, connected to the ample variability of this species. Furthermore, many investigations have been carried out in vitro, with few data available on the effectiveness in biological systems. In this study, the protective effect of essential oils and water-soluble extracts derived from three different cultivars of sweet basil has been evaluated in cultured cardiomyocytes. To verify the effectiveness of supplemented oils/extracts in counteracting oxidative damage, cardiomyocytes were stressed by the addition of hydrogen peroxide. The results indicate that (a) in vitro antioxidant activity is not predictive of biological activity and (b) basil can yield extracts with substantially different protective effects, in relation to composition and extraction techniques. Variation among different cultivars has also been detected.