Linoleic Model System Research Articles

Utilization of Morchella esculenta-mediated green synthesis golden nanoparticles in biomedicine applications

This study aimed to synthesize gold nanoparticles (AuNPs) by hot water extract in room conditions using edible Morchella esculenta (ME) and investigate the bioactive properties of the synthesized Morchella esculenta-based gold nanoparticles (ME-AuNPs). The characterization of the biologically synthesized ME-AuNPs was made using the ultraviolet–visible spectrophotometry, X-ray crystallography, scanning electron microscopy, Fourier transforms infrared spectroscopy, and energy dispersive X-ray spectrum methods. The ME-AuNPs, with a particle size of 16.51 nm, were found to have strong bioactive properties. The antioxidant activity of the ME-AuNPs attempted by metal chelating activity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity and the β-carotene linoleate model system. The activities at 10 mg/mL were 82, 85, and 77% for the chelation of ferrous ions, DPPH scavenging, and β-carotene linoleate tests, respectively. The ME-AuNPs also showed strong antimicrobial activity against various pathogen microorganisms and strong cytotoxic activity in the A549 and HepG2 cell lines. This study demonstrated the possibility of using a cheap and nontoxic fungal extract as a reducing and stabilizing agent for the synthesis of size-controlled, large-scale, and biocompatible AuNPs that could be used in future diagnostic and therapeutic applications.

Determination of Antioxidant and cytotoxic activities of king oyster mushroom mediated AgNPs synthesized with environmentally friendly methods

Synthesizing nanoparticles (NPs) using wild edible fungi with environmentally friendly synthesis methods is more preferred because of the advantages it provides. The fact that its synthesis is easy, economical, non-toxic and has a wide range of uses increases the interest in this subject. The aim of this study was to determine the antioxidant and cytotoxic activity of biomolecular synthesized Pleurotus eryngii silver nanoparticles (PE-AgNPs) against human prostate carcinoma (PC-3), human cervix (HeLa) and breast carcinoma (MCF-7) cells. PE-AgNPs showed significant cytotoxic activity against HeLa, PC-3, MCF-7 cell lines, and also dimethyl sulfoxide solvents of PE-AgNPs applied for their metal chelating activity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity and antioxidant activity using the β-carotene linoleate model system. Biosynthetic PE-AgNPs were found to inhibit the proliferation of PC-3, HeLa and MCF-7 cells with IC50 values of 2.185, 46.594 and 6.169 µg / ml, respectively, during a 24-hour incubation period. With the parallel of increasing concentration (1, 2, 5, 10 mg/mL) the activities were also increased at all the tests studied. At 10 mg/ml antioxidant activities were 82%, 85% and 77% for chelation of ferrous ions reducing power, DPPH scavenging and β-carotene linoleate tests respectively. The results show that PE-AgNPs may contribute to the development of a suitable anticancer drug that can lead to a new development of nanoparticles for cancer treatment. It also appears to be advantageous to use nanotechnology and green chemistry to improve the existing therapeutic properties of P.eryngii.

Comparison of phenolic content and antioxidant activities of millet varieties grown in different locations in Sri Lanka.

Soluble and bound phenolic compounds were extracted from different varieties of millet types namely, finger millet, foxtail, and proso millet cultivated at dry and intermediate climatic zones in Sri Lanka. The extracts were examined for their total phenolic content (TPC), total flavonoid content (TFC), and proanthocyanidin content (PC). The antioxidant activities were meassured by reducing power (RP), trolox equivalent antioxidant capacity (TEAC), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activity, ferrous ion chelating ability (FICA), and using a β carotene linoleate model system. The ferulic acid content of extracts were determined using high‐performance liquid chromatoghraphy (HPLC). Finger millet showed the highest phenolic content and antioxidant activities compared to proso and foxtail millets. The phenolic content as well as antioxidant activites of soluble and bound phenolic extracts of millets were affected by variety and cultivated location. The highest phenolic content and antioxidant activites were reported for millet samples cultivated in areas belonging to the dry zone in Sri Lanka.

Effect of Drought Stress on Total Phenolic, Lipid Peroxidation, and Antioxidant Activity of Achillea Species.

The changes in total phenolic content (TPC), total flavonoid content (TFC), proline, malondialdehyde (MDA), H2O2, and antioxidant activity were assessed based on three model systems in three Achillea species (Achillea millefolium, A. nobilis, and A. filipendulina) growing under four irrigation regimes, including 100% FC (field capacity as normal irrigation) 75% FC (low stress), 50% FC (moderate stress), and 25% FC (severe stress) conditions. The highest TPC (47.13 mg tannic acid/g DW) and TFC (20.86 mg quercetin/g W) were obtained in A. filipendulina under moderate and severe stress conditions. In 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, the highest and the lowest antioxidant activity was obtained for A. millefolium (70.28%) and A. filipendulina (53.21%), respectively, while in the FTC model system A. nobilis revealed the highest antioxidant activity (1.934) in severe drought condition. In the linoleic model system, the highest antioxidant activity was observed under low drought stress condition in A. nobilis. MDA and H2O2 content were increased due to both low (75% FC) and moderate (50% FC) drought stress, but they were decreased under severe stress condition (25% FC). Furthermore, A. millefolium revealed the lowest H2O2 (4.96 nm/g FW) and MDA content (176.32 μmol/g). Investigation of the relationship among different metabolites showed a strong positive correlation with TPC and TFC. Finally, the moderate drought stress treatment (50% FC) was introduced as the optimum condition to obtain appreciable TPC and TFC,, while the highest antioxidant activity was obtained in severe stress condition (25%FC).

Microkinetic modeling of the autoxidative curing of an alkyd and oil-based paint model system

Elucidating the curing and aging mechanisms of alkyd and other oil-based paints is valuable for the fields of conservation and bio-based coatings. Recent research has demonstrated the limitations of artificial aging in predicting the actual properties of paints that are hundreds of years old. Kinetic modeling offers pathways to develop a realistic and dynamic description of the composition of these oil-based paint coatings and facilitates the exploration of the effects of various environmental conditions on their long-term chemical stability. This work presents the construction of a kinetic Monte Carlo framework from elementary steps for the cobalt-catalyzed autoxidative curing of an ethyl linoleate model system up to the formation of single cross-links. Kinetic correlations for reaction families of similar chemistry are employed to reduce the number of parameters required to calculate rate constants in Arrhenius form. The model, developed from mechanisms proposed in the literature, shows good agreement with experiment for the formation of primary products in the early stages of curing. The model has also revealed that the mechanisms proposed in the literature for the formation of secondary products, such as volatile aldehydes, are still not well established, and alternative routes are under evaluation.

Physicochemical characteristics and oxidative stability of de-acidified lampante high acid olive oil

The aim of this investigation was to enhance the quality of high free fatty acid olive oil (HFFAO). Silica gel (SG) was used as adsorbent by applying filtration and stirring techniques. Alkali treatments with NaOH and Ca(OH)2 were also conducted to neutralize high acidity of HFFAO. The levels of linoleic acid (C18:2) in neutralized oils were lower than in reference olive oil. Untreated and treated HFFAO samples were stored under oxidative conditions for 30 days at 60 °C. The progress of oxidation was followed by measuring acid value (AV), the formation of oxidative products [i.e., peroxide value (PV) and p-anisidine value (AnV)], total phenolic compounds (TPC), radical scavenging activity toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and inhibition of β-carotene in a linoleate model system. The results indicated that SG and alkali treatments were effective in reducing the acidity of HFFAO. Alkali treatments reduced the AV of HFFAO, while treatments with SG induced variable degrees of reduction in HFFAO acidity. The percentage of reduction in the PV for HFFAO using SG was in the range of 10.5–47.3 %. Filtration with SG had a significant effect on AnV. Levels of TPC were reduced (ca. 70 %) with alkali treatments, while treatments with SG resulted in reduction of about 22–48 %. After 60 min incubation with DPPH, 78 % of DPPH radicals were quenched by control sample, while HFFAO treated with SG or alkali were able to quench from 48 to 56 %. SG and alkali treatments were not effective in inhibiting the oxidation of linoleic acid and the subsequent bleaching of β-carotene in comparison with control oil. During autoxidation experiments the same trends of results were noted for both control and treated oils. The results stated that SG with permitted high adsorbing capacity reduced free fatty acids levels in HFFAO and the effect was close to that induced with chemical treatments which are used commercially in a large scale to improve oil quality.

Fluorescence and Ultraviolet Spectroscopic Evaluation of Phenolic Compounds, Antioxidant and Binding Activities in Some Kiwi Fruit Cultivars

Spectrophotometric assays (Folin–Ciocalteu, ferric-reducing/antioxidant power, cupric-reducing antioxidant capacity, and β-carotene linoleate model system) have been used to evaluate the total phenolics and flavonoids in kiwi fruit cultivars in ethanol and water extracts. Fluorescent and infrared measurements were correlated with the obtained spectroscopic data. It was found that the contents of the bioactive compounds and the level of antioxidant activity in different extracts differ significantly (p < 0.05). Bioactive compounds and antioxidant activities were significantly higher in two kiwi fruit cultivars (“Bidan” and “SKK12”) than in other studied samples. To our knowledge this is the first report showing the differences and similarities in new kiwi fruit cultivars, using these spectroscopic data. The ethanol extracts of these cultivars exhibited high binding properties with human serum albumin compared with rutin. In conclusion, the applied analytical methods showed the main compounds in the kiwi fruit cultivars and can be used for determination of these compounds in any plants. The relative knowledge would contribute to the pharmaceutical development and clinical application of extracts of kiwi fruit extracts.

Deacidification of High-acid Olive Oil

The objective of the present work was to improve the quality of high-free fatty acid olive (HFFAO) oil. Silica gel (SG) was used as adsorbent by applying filtration and stirring techniques. Chemical treatments with alkali using NaOH and/or Ca(OH)2 were also conducted to neutralize the acidity of HFFAO oil. The percentages of linoleic acid (C18:2) in the neutralized oils were lower than those in the reference olive oil. Untreated and treated HFFAO oil samples were stored under accelerated conditions for 30 days. The progress of oxidation at 60°C was followed by measuring acid value (AV), the formation of oxidative products (peroxide value (PV) and p-anisidine value (AnV)), total phenolic compounds (TPC), recording radical scavenging activity (RSA) toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and inhibition of β-carotene in a linoleate model system. The results indicated that SG and alkali treatments were effective in reducing the acidity of HFFAO oil. Generally, alkali treatments reduced the AV of HFFAO oil, while treatments with SG induced variable degrees of improvements in HFFAO oil acidity. Alkali treatments resulted in increasing the PV levels to 35 and 28 meq peroxide kg−1 oil for HFFAO treated with soda and lime, respectively. The corresponding improvement in the PV reduction (%) for HFFAO oil using SG was in the range of 10.5% to 47.3%.Treatments with SG or alkali resulted in reduction of AnV, wherein filtration with SG had a remarkable effect on AnV. Levels of TPC were reduced (ca. 70%) with alkali treatments, while treatments with SG resulted in reduction of about 22-48%. Antiradical properties of HFFAO oils were compared using stable DPPH free radicals. After 60 min incubation with DPPH, 78% of DPPH radicals were quenched by control sample, while HFFAO oils treated with SG or alkali were able to quench from 48 to 56%. Different SG and alkali treatments were not effective in inhibiting the oxidation of linoleic acid and the subsequent bleaching of β-carotene in comparison with the control. During autoxidation experiments the same trends of results was noted for both control and treated oils. Practical application: Olive oil is one of the most important edible oils in the world. Crude vegetable oils refined to remove free fatty acids (FFA) as well as other impurities that affect flavor, odor and appearance of oils. Deacidification process significantly influences the economics of oil production. Several methods to remove FFA have been developed to enhance the value of degraded vegetable oils, for example, physical refining based on distillation and chemical refining with sodium hydroxide. In this work, the quality of high-free fatty acid olive (HFFAO) oil was improved using silica gel (SG) as an adsorbent by applying filtration and stirring methods. The results stated that SG with small particle size permitted high adsorbing capacity and close to that induced with chemical treatments which are used commercially in a large scale to improve oil quality.

In vitro antioxidant and mineral-chelating properties of natural and autocleaved ovotransferrin.

Egg white proteins can be excellent substrates for the development of functional foods and nutraceuticals. In this study, several in vitro antioxidant methods, namely the β-carotene linoleate model system, the ferric thiocyanate method, the 2-thiobarbituric acid-reactive substances (TBARS) method and copper/calcium ion chelation, were used to determine the antioxidant capacity of natural and autocleaved ovotransferrin. Autocleaved ovotransferrin was prepared by reducing natural ovotransferrin with tris(2-carboxyethyl)phosphine (TCEP) for 6 h at 37 °C. Autocleaved ovotransferrin suppressed the discoloration of β-carotene effectively and prevented the oxidation of linoleic acid during 5 days of storage at 4 °C. However, the concentration of autocleaved ovotransferrin had no influence on its antioxidant effect. Similarly, the highest TBARS values were obtained from autocleaved ovotransferrin (>90%) and the lowest value in natural ovotransferrin (24%) during incubation at 37 °C for 48 h. The hydrolysates obtained from autocleaved ovotranferrin showed better copper/calcium-solublilizing activity than those from natural ovotransferrin. The results indicated that autocleaved ovotransferrin has the potential to be used as a natural antioxidant in foods.

Effect of boiling in water of barley and buckwheat groats on the antioxidant properties and dietary fiber composition.

In recent years, there has been an ever-increasing interest in the research of polyphenols obtained from dietary sources, and their antioxidative properties. The purpose of this study was to determine the effect of boiling buckwheat and barley groats on the antioxidant properties and dietary fiber composition. Antioxidative properties were investigated using methyl linoleate model system, by assessing the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity and metal chelating activity. The results were compared with butylated hydroxytoluene (BHT). Raw barley and buckwheat groats extracts showed higher DPPH scavenging ability compared to boiled barley and buckwheat groats extracts. Raw barley groats extract exhibited higher antioxidant activity than boiled groats extract in the methyl linoleate emulsion. Higher chelating ability in relation to Fe (II) ions was observed for boiled groats extracts as compared to raw groats extracts. BHT showed small antiradical activity and metal chelating activity, while showing higher antioxidative activity in emulsion system. The analysis of groats extracts using HPLC method showed the presence of rutin, catechin, quercetin, gallic, p-hydroxybenzoic, p-coumaric, o-coumaric, vanillic, sinapic, and ferulic acids. Differences in the content of dietary fiber and its fractions were observed in the examined products. The highest total dietary fiber content was detected in boiled buckwheat groats, while the lowest - in boiled barley groats. The scientific achievements of this research could help consumers to choose those cereal products available on the market, such as barley and buckwheat groats, which are a rich source of antioxidative compounds and dietary fiber.

Corn starch-calcium alginate matrices for the simultaneous carrying of zinc and yerba mate antioxidants

A new strategy for the simultaneous carrying of zinc and yerba mate antioxidants into starch-alginate matrices was developed. Firstly, the use of native corn starch as vehicle of zinc was evaluated and then the starch-zinc carriers were incorporated into calcium alginate beads containing antioxidant extract of yerba mate. The loading capacity and the antioxidant activity of the beads were determined. Moreover, the systems were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR) and differential scanning calorimetry (DSC). Compartmentalized beads containing yerba mate polyphenols and zinc were obtained without affecting their morphological aspect. Moreover, the encapsulating systems exhibited a high antioxidant activity assayed by both, β-carotene linoleate model system and DPPH radical scavenging method. FT-IR and DSC analysis revealed that interactions between the active compounds and the encapsulating matrix were not formed. The proposed methodology constituted a useful strategy for the simultaneous transport of yerba mate antioxidants and zinc by preventing a possible interaction between them. The new beads could be incorporated into food formulations for preserving substances prone to oxidation and for providing compounds with beneficial properties for health.

α-Glucosidase Inhibition and Antioxidant Properties of Streptomyces sp.: In Vitro

Streptomyces strain isolated from the soil sediment was studied for its in vitro α-glucosidase and antioxidant properties. Morphological characterization and 16S rRNA partial gene sequencing were carried out to confirm that the strain Loyola AR1 belongs to genus Streptomyces sp. Modified nutrient glucose broth was used as the basal medium for growth and metabolites production. Ethyl acetate extract of Loyola AR1 (EA-Loyola AR1) showed 50% α-glucosidase inhibition at the concentration of 860.50 ± 2.68 μg/ml. Antioxidant properties such as total phenolic content of EA-Loyola AR1 was 176.83 ± 1.17 mg of catechol equivalents/g extracts. EA-Loyola AR1 showed significant scavenging activity on 2,2-diphenyl-picrylhydrazyl (50% inhibition (IC₅₀), 750.50 ± 1.61 μg/ml), hydroxyl (IC₅₀, 690.20 ± 2.38 μg/ml), nitric oxide (IC₅₀, 850.50 ± 1.77 μg/ml), and superoxide (IC₅₀, 880.08 ± 1.80 μg/ml) radicals, as well as reducing power. EA-Loyola AR1 showed strong suppressive effect on lipid peroxidation (IC₅₀, 670.50 ± 2.52 μg/ml). Antioxidants of β-carotene linoleate model system reveals significantly lower than butylated hydroxyanisole.

In Vitro α-Glucosidase Inhibition and Antioxidative Potential of an Endophyte Species (Streptomyces sp. Loyola UGC) Isolated from Datura stramonium L

Endophytic actinomycetes isolated from Datura stramonium L. was evaluated for its effects against in vitro α-glucosidase inhibition, antioxidant, and free radical scavenging activities. Based on microbial cultural characteristic and 16S rRNA sequencing, it was identified as Streptomyces sp. loyola UGC. The methanolic extract of endophytic actinomycetes (MeEA) shows remarkable inhibition of α-glucosidase (IC50 730.21±1.33μg/ml), scavenging activity on 2,2-diphenyl-picrylhydrazyl (DPPH) (IC50 435.31±1.79μg/ml), hydroxyl radical (IC50 350.21±1.02μg/ml), nitric oxide scavenging (IC50 800.12±1.05μg/ml), superoxide anion radical (IC50 220.31±1.47μg/ml), as well as a high and dose-dependent reducing power. The MeEA also showed a strong suppressive effect on rat liver lipid peroxidation. Antioxidants of β-carotene linoleate model system revels significantly lower than BHA. The total phenolic content of the extract was 176mg of catechol equivalents/gram extract. Perusal of this study indicates MeEA can be used as natural resource of α-glucosidase inhibitor and antioxidants.

Antioxidant activity of phytosteryl phenolates in different model systems

As part of a comprehensive study of the physiochemical and biological properties of phytosteryl phenolates, successfully synthesized chemoenzymatically in our lab, their antioxidant activity was evaluated using three different in vitro model systems, namely bulk oil model system, β-carotene-linoleate model system and low-density lipoprotein cholesterol (LDL-C) oxidation assay. In the bulk oil system, phytosteryl phenolates showed similar or lower antioxidant activity compared with those of phenolic acids. However, in β-carotene-linoleate assay, an emulsion model system, phytosteryl phenolates showed enhanced antioxidant activity except phytosteryl ferulates. Moderate inhibitory effect of LDL-C oxidation by phytosteryl phenolates was observed. These findings demonstrate that use of multidimensional antioxidant activity determinations with differing reaction mechanisms is necessary to provide an overall understanding of the mechanisms of antioxidant action of phytosteryl phenolates.

Synergistic effect of lecithins for tocopherols: lecithin-based regeneration of α-tocopherol

Phospholipids synergistically enhance the antioxidant effect of phenolic antioxidants. Mixtures of lecithins, ascorbic acid and tocopherols are known as strong antioxidants. In our study, the mechanism of the synergistic effect of phospholipids with tocopherols was investigated. The oxidative deterioration and the degradation of tocopherols were analyzed in degummed rapeseed oil or in mixtures with ethyl linoleate at 25 or 110 °C. It was shown that lecithins reduce the degradation of tocopherols in rapeseed oil or in ethyl linoleate model system at 25 or 110 °C. It was found that phosphatidylethanolamine (PE) and phosphatidylserine (PS) can regenerate α-tocopheryl quinone (α-TQ) to α-tocopherol at elevated temperatures. The regeneration could be catalyzed by acetic acid. The synergistic effect of PE or PS with α-tocopherol and l-ascorbic acid resulted from the regeneration of α-TQ to α-tocopherol, because PE, l-ascorbic acid and α-tocopherol show the same stabilization effect upon ethyl linoleate as PE, l-ascorbic and α-TQ. Phosphatidylcholine as a non-amine phospholipid does not regenerate α-TQ. However, it improves the regeneration of α-tocopherol from α-tocopheroxyl radicals with l-ascorbic acid in ethyl linoleate through its ability to acts as a phase transfer catalyst between the polar l-ascorbic acid and the unpolar α-tocopheroxyl radicals. A mechanism for the regeneration of α-TQ by PE or PS is suggested. The activation of α-TQ by PE or PS and the formation of α-tocopherones are the key steps of the mechanism.

Antioxidants in mangrove plants and endophytic fungal associations

Abstract The manner in which fungal endophytes activate host stress response systems is unknown; the occurrence of additional mechanisms involved in symbiotically-conferred stress tolerance in mangrove plants (the primary producers of estuarine food chain) is also an unresolved issue. Here, we report antioxidant potentials of four different mangroves and their endophytic fungi. We elucidated the possible roles of antioxidants in symbiotic association between mangroves and their endophytic fungi. Four different mangrove species and the predominant endophytic fungus Aspergillus flavus were analyzed using various in vitro assay systems (such as iron chelating capacity, reducing power, and hydroxyl radicals/hydrogen peroxide/l-diphenyl-2-picrylhydrazyl radical scavenging and inhibition of lipid peroxidation using the β-carotene–linoleate model system). In vitro models clearly established the antioxidant potency of extracts of mangrove plants and their respective endophytic fungi, which aids in understanding the mutualistic associations of plant and endophyte against various biotic and abiotic stresses. Re-infection analysis of endophytic A. flavus in tobacco plants confirmed the endophytic status of the fungus and its enhancement effect on plant growth.

Antioxidant compounds from Rosalaevigata fruits

Rosa laevigata fruit is a foodstuff used in China to brew wine, extract brown pigments, and make a healthy vinegar-based beverage. It is also widely used in traditional Chinese medicine to treat nephropathy. We isolated 20 compounds from the fruit, including two new lignans, rosalaevins A and B (1 and 2), and 18 phenolic compounds isolated for the first time. Their antioxidant potentials were evaluated with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and ferric reducing antioxidant power (FRAP) assays, and a beta-carotene linoleate model system. Several compounds exhibited powerful antioxidant capacities. No compound inhibited nitric oxide production in macrophage cells. These results provide new insights into the role of R. laevigata fruit in the prevention of nephropathy, and may lend support to the development of this fruit as a health-promoting food. (C) 2011 Elsevier Ltd. All rights reserved.

In vitro antioxidant properties of red algal polysaccharides

Abstract The present study was devoted to in vitro antioxidant properties of lambda-, iks-, kappa-, kappa/beta- and kappa/iota-carrageenans from red algae of Gigartinaceae and Tichocarpaceae families collected from the Russian Pacific Coast. In vitro antioxidant capacity of carrageenans with different structural types was assessed by measuring their ferric-reducing antioxidant capacity, relative antioxidant capacity (phosphomolybdenum assay), and their scavenging effect on hydroxyl radicals, superoxide anion, nitric oxide and hydrogen peroxide. Influence of pH value on potential antioxidant capacity was also been investigated by means of linoleic model system. The reducing capacity of the investigated carrageenans was not much expressed, and capacity of the commercial polysaccharide samples was negligible. Iks-carrageenan containing three sulphate groups per disaccharide unit and a 3,6-anhydrogalactose unit was among the most effective superoxide anion (54.83% at the concentration of 1 mg/mL) and nitric oxide scavengers (37.26% at the concentration of 0.25 mg/mL) and the only polysaccharide possessing iron ion chelating capacity. Antioxidant actions of lambda-, iks-, kappa-, kappa/beta- and kappa/iota-carrageenans against reactive oxygen/nitrogen species depend on polysaccharide concentration and such fine structural characteristics as presence of hydrophobic 3,6-anhydrogalactose unit, amount and position of sulphate groups, and an oxidant agent, on which sample antioxidant action is directed. The results indicated that carrageenans possess antioxidant capacity in vitro , and this action notably depends on the structure of the polysaccharide itself than the reducing capacity of the polysaccharides.

Targeting excessive free radicals with peels and juices of citrus fruits: Grapefruit, lemon, lime and orange

A comparative study between the antioxidant properties of peel (flavedo and albedo) and juice of some commercially grown citrus fruit (Rutaceae), grapefruit (Citrus paradisi), lemon (Citrus limon), lime (Citrusxaurantiifolia) and sweet orange (Citrus sinensis) was performed. Different in vitro assays were applied to the volatile and polar fractions of peels and to crude and polar fraction of juices: 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, reducing power and inhibition of lipid peroxidation using beta-carotene-linoleate model system in liposomes and thiobarbituric acid reactive substances (TBARS) assay in brain homogenates. Reducing sugars and phenolics were the main antioxidant compounds found in all the extracts. Peels polar fractions revealed the highest contents in phenolics, flavonoids, ascorbic acid, carotenoids and reducing sugars, which certainly contribute to the highest antioxidant potential found in these fractions. Peels volatile fractions were clearly separated using discriminant analysis, which is in agreement with their lowest antioxidant potential.

Antioxidant activity of Portuguese honey samples: Different contributions of the entire honey and phenolic extract

The antioxidant activity of Portuguese honeys was evaluated considering the different contribution of entire samples and phenolic extracts. Several chemical and biochemical assays were used to screen the antioxidant properties of entire honeys with different colour intensity and phenolic extracts: reducing power, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging capacity, and inhibition of lipid peroxidation using the β-carotene linoleate model system and the thiobarbituric acid reactive substances (TBARS) assay. The amounts of phenols, flavonoids, ascorbic acid, β-carotene, lycopene and sugars present in the samples were also determined. The highest antioxidant contents and the lowest EC50 values for antioxidant activity were obtained in the dark honey. An analysis of variance was carried out to evaluate the influence of the colour intensity and extraction method in the antioxidant properties and phenolic contents. A discriminant analysis was also performed, giving satisfactory results once the six samples were clustered in six individual groups obtained through the definition of two discriminant analysis dimensions.