Synergism and antagonism between quercetin and other chain-breaking antioxidants in lipid systems of increasing structural organisation

Antioxidative effect of quercetin was affected differently in neat sunflower oil, in methyl linoleate o/w emulsion and in phospholipid liposomes by the other chain-breaking antioxidants, α-tocopherol, rutin and astaxanthin. Quercetin was better than or comparable to α-tocopherol as an antioxidant in the three lipid systems. The presence of α-tocopherol showed a strong synergistic effect for quercetin in the emulsion, less in the liposomes and a clear antagonistic effect in the neat oil. Astaxanthin, without any effect alone in neat oil or in the liposomes, but with some effect in the emulsion, did not affect quercetin as an antioxidant. Rutin was only effective as an antioxidant in the liposomes where rutin showed clear synergism with quercetin. The interaction of quercetin with the other antioxidants is classified according to the structural organisation of the lipid substrate.     

Effects of chitosan and collagen containing α-tocopherol on the oxidative stability in bulk oil and oil-in-water emulsion

To provide efficient antioxidant capacities, proper carriers are needed to protect antioxidants against oxidative stress. Collagen mesh structure or chitosan gel was loaded with α-tocopherol and their effects were evaluated in bulk corn oil or oil-in-water (O/W) emulsion at 60 °C. Added collagen and chitosan enhanced oxidative stability in corn oil and O/W emulsions at 60 °C compared to corn oils without carriers or with addition of α-tocopherol (p < 0.05). Stability of α-tocopherol in corn oil loaded in collagen or chitosan was significantly enhanced compared to that in oils without carriers (p < 0.05). In O/W emulsions, α-tocopherol loaded collagen showed higher antioxidant properties than α-tocopherol loaded chitosan (p < 0.05). Collagen mesh structure and chitosan gel retarded the rates of lipid oxidation efficiently in both food matrices when α-tocopherol was not loaded. Collagen mesh structure and chitosan gel can be useful carriers for α-tocopherol in bulk oil or O/W emulsion.     

Evaluation of Antioxidant Activity of Rosemary Extracts,Carnosol and Carnosic Acid in Bulk Vegetable Oils and Fish Oil and Their Emulsions

The antioxidant effectiveness of two rosemary extracts, carnosol and carnosic acid, was significantly influenced by the type of system tested (bulk oils vs oil-in-water emulsions), by the oil substrates, the methods used to follow oxi-dation, and the concentrations of test compounds. The rosemary extracts and compounds effectively inhibited conjugated diene hydroperoxide formation in corn oil, soya bean oil, peanut oil and fish oil, when tested in bulk. Test compounds also inhibited hexanal formation in bulk vegetable oils, and propanal and pentenal formation in bulk fish oils. In contrast, these test compounds were either inactive or promoted oxidation in the corresponding vegetable oil-in-water emulsions. In fish oil emulsions, however, the rosemary compounds inhibited the formation of conjugated diene and pentenal but not that of propanal. Interfacial phenomena may explain why the hydrophilic rosemary antioxidants afford more protection in the bulk oil systems by being oriented in the air–oil interface, and less protection in the oil-in-water emulsion systems by partitioning into the water phase.     

Antioxidants in lipid foods and their impact on food quality

This paper reviews the antioxidant properties of tocopherols and ascorbic acid in edible oils, and the impact of interfacial phenomena on their activities in emulsions and the effects of edible oil processing. Tocopherols are the most important natural antioxidants found in vegetable oil-derived foods. These antioxidants can interrupt lipid autoxidation by interfering with either the chain propagation or the decomposition processes. α-Tocopherol at high concentrations inhibits hydroperoxide decomposition but promotes hydroperoxide formation. The effect of antioxidants in inhibiting hydroperoxide decomposition may thus be critical in preserving food quality by reducing rancidity due to aldehyde formation. Ascorbic acid can regenerate α-tocopherol, inactivate metal initiators and reduce hydroperoxides. The activity of natural antioxidants is greatly affected by complex interfacial phenomena in emulsions and multi-component foods. In an oil-in-water emulsion system, the lipophilic antioxidants α-tocopherol and ascorbyl palmitate are more effective than in bulk oil, while the opposite trend is found for the hydrophilic antioxidants Trolox and ascorbic acid. The methodology to evaluate natural antioxidants must be carefully interpreted depending on whether oxidation is carried out in bulk oils or in emulsions, and what method is used to measure lipid oxidation.     

Activity of caffeic acid in different fish lipid matrices: A review

Caffeic acid, a hydroxycinnamic acid common in different vegetable sources, has been employed as a natural antioxidant for inhibiting oxidation of fish lipids present in different food matrices. The aim of this review is to discuss the mechanisms involved in the antioxidative and prooxidative effects of caffeic acid found in different model systems containing fish lipids. These model systems include bulk fish oils, liposomes from cod roe phospholipids, fish oil emulsions, washed cod mince, regular horse mackerel mince and a fish oil fortified fitness bar. The data reported show that the antioxidant activity depends on the physical state of the lipids and the composition of the intrinsic matrix in which they are situated. Caffeic acid significantly prevented rancidity in both unwashed and washed fish mince, the latter which was fortified with haemoglobin. In the unwashed mince, the activity was however clearly dependent on the lipid to antioxidant ratio. In these systems, an important redox cycle between caffeic acid and the endogenous reducing agents ascorbic acid and tocopherol were further thought to play an important role for the protective effects. The effect of caffeic acid was also highly dependent on the storage temperature, showing higher effectiveness above than below 0 °C. Caffeic acid was not able to inhibit oxidation of bulk fish oils, fish oil in water emulsions and the fish-oil enriched fitness bar. In the liposome system, caffeic acid inhibited haemoglobin (Hb)-promoted oxidation but strongly mediated Fe²⁺ mediated oxidation. In conclusion, caffeic acid can significantly prevent Hb-mediated oxidation in fish muscle foods but its activity in food emulsions and liposomes is highly dependent on the pH, the emulsifier used and the prooxidants present.     

Effects of different polarity of onion skin extracts on antioxidative properties and non-volatile profiles

Onion skins are agricultural by-products that contain high levels of antioxidants, including quercetin and protocatechuic acid. The solubility of extracts can affect their antioxidant capacity in food oil matrices. The antioxidative properties of onion skin extracts with different polarity were compared and the chemical profiles of the extracts were identified by GC-MS. Highly lipophilic, moderately hydrophilic and highly hydrophilic onion skin extracts (HLE, MHE and HHE, respectively) were prepared and their antioxidant properties were tested using in vitro assays and bulk oil or oil-in-water (O/W) emulsions. The most abundant phenolic compounds in the onion skin extracts were quercetin and protocatechuic acid. The lipophilicity levels of HLE, MHE and HHE were 0.674, 0.394 and −1.225, respectively. HLE showed higher antioxidant capacity in bulk oil and O/W emulsion matrices compared to MHE and HHE. The antioxidant capacity of HLE was higher in the O/W emulsion than in the bulk oil system. Therefore, highly lipophilic onion skin extracts can be used as effective natural antioxidants in oil matrices, especially O/W emulsions.     

Effects of blackcurrant seeds and rosemary extracts on oxidative stability of bulk and emulsified lipid substrates

The effects of blackcurrant seeds extract and commercially available rosemary extracts on rapeseed oil and rapeseed oil triacylglycerol oxidative stability were evaluated. The antioxidant activity of plant extracts was investigated, both in bulk and emulsified lipid substrates, and compared with those of α-tocopherol and BHT. The investigation showed that blackcurrant seeds and rosemary extracts are the source of active antioxidants and are appropriate for food lipid stabilization. The extracts performed better in stripped substrates as they may interfere with native tocopherols present in rapeseed oil and show different activity according to the presence of water. α-Tocopherol, a 200 ppm, was inactive in bulk and emulsified rapeseed oil but was an effective antioxidant in triacylglycerols. BHT showed the best performance of all used additives in emulsified substrates.     

Evaluation of the Chemical Composition and Antioxidant Activity of the Peel Oil of Citrus nobilis

Peel oil of Citrus nobilis (Lour) was analyzed for determining its chemical composition. Fourteen identified components accounted for 99.1% (GC) and 100.0% (FID) of the total oil. Major component of the oil was limonene (76.8%-GC and 86.2%-FID). Essential oil was also evaluated for its antioxidant activity in four complementary test systems namely; β-carotene/linoleic acid, DPPH radical scavenging, reducing power and metal chelating activities. In the first system, antioxidant activity increased with the increasing concentration. At 20.0 mg.ml^?1 concentration, antioxidant property of the oil was 96.8% ± 0.2 and as strong as the positive controls BHT and α-tocopherol. Scavenging effect of the oil was superior to the positive controls BHT and α-tocopherol at 1.5 mg.ml^?1 concentration (96.4% ± 0.1). Reducing power and chelating effect of the essential oil increased with the increasing concentration.     

Antioxidant and pro-oxidant activity of green tea extracts in marine oils

The activity of green tea extracts (GTE) on the oxidation of refined, bleached and deodorized (RBD) seal blubber oil (SBO) and menhaden oil (MHO) was examined under Schaal oven conditions at 65 °C. Progression of oxidation was monitored using weight gain, peroxide value (PV) and 2-thiobarbituric acid-reactive substances (TBARS) data. GTE exhibited a pro-oxidant effect in both oils examined, perhaps due to the catalytic effect of their chlorophyll constituents. Therefore, in follow-up experiments, a column chromatographic technique was employed to remove chlorophyll from GTE. The resultant dechlorophyllized green tea extract (DGTE) was applied to both SBO and MHO at 100, 200, 500 and 1000 ppm levels. The antioxidant activity of DGTE was compared with the effects of the commonly-used antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) at 200 ppm and α-tocopherol at 500 ppm. DGTE at ≥200 ppm exhibited excellent antioxidant activity in both oils and its efficacy was higher than that of BHA, BHT and α-tocopherol, but less than that of TBHQ.     

栎皮酮的抗氧化性能研究

栎皮酮是一种天然的食品抗氧化剂,通过诱导时间实验与烘箱贮藏实验测定了栎皮酮的抗氧化性能.研究发现,栎皮酮能显著延长花生油、棕榈油和猪板油的诱导时间,同时能提高这3种油样的贮藏稳定性.栎皮酮分别与BHT、TBHQ复配使用时,其协同作用并不明显.     

Effects of sesamol, sesamin, and sesamolin extracted from roasted sesame oil on the thermal oxidation of methyl linoleate

This study investigated the effects of lignan compounds extracted from roasted sesame oil, which were sesamol, sesamin, and sesamolin, on oxidation of methyl linoleate (ML) during heating. These compounds were added at 500 or 1000 mg/kg to ML, and α-tocopherol was used as a reference antioxidant. The ML added with lignans or α-tocopherol was heated at 180 °C for 60 min. Thermal oxidation of ML was evaluated by conjugated dienoic acid (CDA) contents, p-anisidine value (PAV), and ML retention. Contents changes of lignan compounds or α-tocopherol in ML during heating were monitored by high-performance liquid chromatography. CDA contents and PAV of samples increased and ML decreased with heating time at 180 °C. Samples added with lignan compounds showed lower CDA contents and PAV but higher ML retention than samples without lignan compounds. The antioxidant activity of sesame oil lignan compounds in ML oxidation during heating tended to be higher than that of α-tocopherol. The contents of lignan compounds in samples decreased with heating time due to their degradation, but the degradation rates were lower than that of α-tocopherol. This study suggested that sesame oil lignan compounds be used as antioxidants in oil at high temperatures for deep-fat frying due to their higher effectiveness and stability than α-tocopherol.     

STABILIZATION OF MARINE OILS WITH FLAVONOIDS

Antioxidant activity of a number of flavonoids in refined-bleached and deodorized (RBD) seal blubber oil (SBO) and menhaden oil (MHO) was compared with that of commercially used antioxidants, namely butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) as well as α-tocopherol. The study was carried under Schaal oven conditions at 65C and progression of oxidation was followed by monitoring weight gain, peroxide value (PV) and 2-thiobarbituric acid reactive substances (TBARS) value. Among the flavonoids tested in this study, the flavonols, namely myricetin, quercetin and morin exhibited a stronger antioxidant activity than BHA and BHT and effectively stabilized both SBO and MHO. Myricetin was the most effective flavonoid tested in this study and its effect in reducing lipid oxidation was similar to that of TBHQ.     

Palm-tocotrienol rich fraction (TRF) is a more effective inhibitor of LDL oxidation and endothelial cell lipid peroxidation than α-tocopherol in vitro

Comparative protective effects of palm tocotrienol rich fractions (TRF) and α-tocopherol on the copper-induced oxidation of plasma low density lipoprotein (LDL) and indices of lipid peroxidation in human umbilical vein endothelial cells (HUVEC) were investigated. LDL (100 μg protein/ml) was incubated at 37 °C with 1 μM CuSO₄ with or without the presence of 50 μM (TRF) or 50 μM α-tocopherol. Aliquots were collected at 0,1,2,3,6,9,12 and 24 h and thiobarbituric acid reactive substances (TBARS) determined. In the absence of antioxidant, TBARS increased significantly in LDL reaching a maximum after 6 h. α-Tocopherol and TRF delayed TBARs formation by 6 h with a maximum effect after 12 h. The rate of TBARs formation with TRF was significantly slower than with α-tocopherol, indicating a higher antioxidant efficacy for TRF. Low density lipoprotein isolated from volunteers consuming low or high polyunsaturated fatty acid (PUFA) diets were similarly incubated with 1 μM CuSO₄ with or without 50 μM TRF or 50 μM α-tocopherol. LDL oxidation was not significantly different between low and high PUFA groups. However, LDL treated with TRF was better protected against copper-induced oxidation than that treated with α-tocopherol. In HUVEC pre-incubated with 100 μM arachidonic acid, 25 μM TRF treatment decreased TBARS by ∼73% compared to ∼50% with 25 μM of α-tocopherol. Higher concentrations of TRF did not further decrease TBARS formation in the medium. However, treatment with higher concentrations of α-tocopherol again increased TBARS formation. Formation of conjugated diene in HUVEC subjected to arachidonic acid (ARA)-induced oxidative stress was decreased equally with either 10 μM TRF or 25 μM α-tocopherol. Results suggest that TRF is a more potent antioxidant than α-tocopherol, at least in vitro.     

Green tea extract as food antioxidant. Synergism and antagonism with α-tocopherol in vegetable oils and their colloidal systems

The antioxidant effects of α-tocopherol (TOH) in combination with green tea extract (GTE), the green tea polyphenol (−)-epicatechin (EC) or the isomeric (+)-catechin (C), were investigated using different lipid systems based on high linoleic sunflower oil: bulk oil, o/w-emulsion and a phosphatidylcholine-based liposome system. Both polyphenols as well as TOH were efficient antioxidants in all systems when used alone, as detected by the formation of free radicals and conjugated dienes and by oxygen consumption. Strong synergistic effect was found for the combination of TOH and GTE in a methyl linoleate o/w-emulsion and in the pure bulk oil, while only an additive effect was observed in a liposome system. The synergism was already evident for the tendency for radical formation in the bulk oil as detected by electron spin resonance (ESR) spectroscopy. On the contrary, combinations of TOH with either EC or C showed clear synergistic effects in both heterogeneous systems, but antagonistic or additive effects in bulk oil. GTE may accordingly be used to protect both vegetable oils and their emulsions against oxidation through enhancement of the activity of their endogenous antioxidants, while GTE is less efficient in the protection of phospholipids as in liposomes.     

Oxidative Stability in Oil‐in‐Water Emulsions with Quercetin or Rutin Under Iron Catalysis or Riboflavin Photosensitization

The effects of quercetin and rutin on the oxidative stability of oil‐in‐water (O/W) emulsions were tested under riboflavin (RF) photosensitization in the presence or absence of FeCl₂. The degree of oxidation in O/W emulsions was determined by headspace oxygen content, conjugated dienes, and lipid hydroperoxides. Quercetin chelated more metal than did rutin in iron catalyzed O/W emulsions. Generally, 0.1 mM quercetin and rutin was oxidative while 0.5 and 1.0 mM quercetin and rutin was antioxidative in O/W emulsions under RF photosensitization. Depending on the analysis method, the antioxidants had different strengths. The antioxidative or oxidative properties of quercetin and rutin vary in O/W emulsions and depend the quercetin and rutin concentrations and oxidative forces like transition metals, RF photosensitization, or a combination thereof.     

Effect of phenolic antioxidants on the dispersion state and chemical stability of olive oil O/W emulsions

The effect of gallic acid, catechin and quercetin on physical and chemical stability of olive oil-in-water emulsions was investigated. These molecules, characterised by different polarity and antioxidant activity, showed different interface activity and efficiency in delaying lipid oxidation. Gallic acid contributed positively to stabilise the colloidal properties of the systems toward physical instability whilst showed a low activity towards secondary oxidation. Catechin showed an interfacial localisation which was reflected in the enhancement of primary oxidation and in the inhibition of secondary oxidation. Quercetin poorly partitioned in the aqueous phase and was proven not to slow down the bimolecular phase of auto-oxidation.Results confirmed that polarity is not the only parameter to determine efficiency of antioxidants in emulsions but other variables, such as its antioxidant activity in terms of capacity and rapidity in donating an hydrogen atom, can affect its protective role towards lipids auto-oxidation in emulsions.     

Effects of flavonoids on physical and oxidative stability of soybean oil O/W emulsions

Flavonoids have attracted attention due to pharmacological and antioxidative activities. The effects of flavonoids on the physical and oxidative stabilities of lecithin emulsified soybean oil-in-water (O/W) emulsions were investigated at 25°C during 29 days of storage. Addition of 100 ppm hesperidin, hesperitin, rutin, or quercetin improved the physical stability of O/W emulsions but did not change particle size values, compared to a control with no flavonoids during storage. Quercetin showed the highest antioxidant activity for inhibition of lipid oxidation based on lowered lipid hydroperoxide formation and 2-thiobarbituric acid reactive substances values in emulsions, followed by rutin, hesperitin, and hesperidin. Hesperidin and hesperitin did not affect antioxidative activities in O/W emulsions under metal ion-catalyzed conditions. Addition of hesperidin, hesperitin, rutin, and quercetin to soybean oil O/W emulsions improved the physical and oxidative stability of emulsions lacking added metal ions.     

ANTIOXIDANT EFFICACY OF EXTRACTS OF AN EDIBLE RED ALGA (GRATELOUPIA FILICINA) IN LINOLEIC ACID AND FISH OIL

The antioxidant activity of an extract of a marine red alga (Grateloupia filicina) was evaluated in linoleic acid and fish oil induct period oil at 65C. Oxidative stability of the oils was evaluated by employing peroxide value (PV), 2-thiobarbituric acid reactive substances (TBARS), conjugated diene (CD) and weight gain experiments. The algal extract was applied to linoleic acid and fish oil at 0.01, 0.03 and 0.05% and results were compared with those of commercial antioxidants such as butylated hydroxytoluene (BHT), butylated hydroxyanisol (BHA) and α-tocopherol at 0.01 %. Results indicated the ability of the alga extract to inhibit oxidation of linoleic acid and fish oil; at α 0.05%     

Activity of plant extracts for preserving functional food containing<Emphasis Type="Italic"> n</Emphasis>-3-PUFA

The ability of antioxidants obtained from natural sources to stabilise foodstuffs containing long n-3 fatty acids of marine origin has been determined. Food systems enriched in polyunsaturated fatty acids (PUFA) were: emulsified horse mackerel (Trauchurus trauchurus) muscle, fish oil-in-water emulsions (4% of n-3 PUFA) and fish oils (40% of n-3 PUFA). Rosemary leaves and extra virgin olive oil (EVO) were employed as sources of natural phenolic antioxidants. Both vegetable extracts were able to retard lipid oxidation in the different lipid systems. Rosemary extracts with a high content of carnosoic acid showed a significant synergism with fish proteins, by reinforcing their antioxidative effectiveness. Fish proteins and EVO-phenolics showed minor cooperative effects for inhibiting oxidation. The antioxidative partition into the different phases in the emulsified systems showed minor amounts of phenolics in the aqueous phases, except hydroxytyrosol and tyrosol, and a high adsorption on fish muscle.An erratum to this article can be found at     

Antioxidant activity of hydroxytyrosol in frankfurters enriched with n-3 polyunsaturated fatty acids

The capacity of hydroxytyrosol (HXT) to inhibit lipid oxidation in cooked pork meat batter, oil-in-water emulsions and potential functional frankfurters formulated with a healthier oil combination (as animal fat replacer) was studied during chilling storage, and its effect compared with those produced by synthetic antioxidants (BHA/BHT). Although efficiency varied, HXT was an effective antioxidant during chilling storage in the three food matrices studied. In general the order of inhibition capacity of HXT against lipid oxidation (thiobarbituric acid-reactive substances-TBARS) was cooked meat batter > oil-in-water emulsion > frankfurters, whereas in the case of BHA/BHT (with lower inhibitory activity than HXT) it was cooked meat batter > oil-in-water emulsion, and there was no antioxidative effect in frankfurters. Whereas significant correlations were established between lipid oxidation (TBARS) and antioxidative capacity measured by photochemiluminescence (PCL) in frankfurters supplemented with HXT and BHA/BHT, no significant correlations were found between ferric reducing/antioxidant power assay (FRAP) and TBARS and PCL.