Determination of the total antioxidant activity of fruits and vegetables by a liposome assay

The effects of mixtures of antioxidants on the oxidation of phospholipids have been investigated in large unilamellar liposomes following initiation by 2,2'-azobis(2-aminopropane) dihydrochloride. The lag phase increased linearly with antioxidant concentration. The lag phases of mixtures containing alpha-tocopherol with ascorbic acid showed synergy between the antioxidants, but mixtures of beta-carotene with cc-tocopherol or ascorbic acid were not synergistic. The liposome system was used to investigate the total antioxidant activity of lipid- and water-soluble extracts from 16 samples of fruits, vegetables, and related food products. The water-soluble extracts caused greater increases in lag phase than the lipid-soluble extracts. The lag phase of liposomes containing the water-soluble extracts from fruits and vegetables increased linearly with the total phenolic concentration, with the continental salad extract having the longest lag phase. The lipid-soluble extract from apples caused the largest increase in lag phase of the lipid-soluble extracts. The lag phases of the lipid-soluble and water-soluble extracts of all fruits and vegetables studied were additive, but no synergy was detected. The lag phase of the liposomes containing both the water-soluble and lipid-soluble extracts varied from 611.5 min for the continental salad extracts to 47.5 min for the cauliflower extracts.

The influence of ripening stage and cultivation system on the total antioxidant activity and total phenolic compounds of yellow passion fruit pulp

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of the cultivation system in the aroma of the volatile compounds and total antioxidant activity of passion fruit

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Enhancement of the total phenolic compounds and antioxidant activity of aqueous Citrus limon L. pomace extracts using microwave pre-treatment on the dry powder

The effect of microwave pre-treatment on the levels of total phenolic compounds, flavonoids, proanthocyanidins and individual major compounds as well as the total antioxidant activity of the dried lemon pomace was investigated. The results showed that microwave pre-treatment significantly affected all the examined parameters. The total phenolic content, total flavonoids, proanthocyanidins, as well as the total antioxidant activity significantly increased as the microwave radiation time and power increased (e.g., 2.5 folds for phenolics, 1.4 folds for flavonoids and 5.5 folds for proanthocyanidins), however irradiation more than 480 W for 5 min resulted in the decrease of these parameters. These findings indicate that microwave irradiation time and power may enhance higher levels of the phenolic compounds as well as the antioxidant capacity of the dried lemon pomace powder. However, higher and longer irradiation may lead to a degradation of phenolic compounds and lower the antioxidant capacity of the dried lemon pomace.

A novel near-infrared spectroscopy and chemometrics method for rapid analysis of several chemical components and antioxidant activity of mint (mentha haplocalyx briq.) samples

A novel near-infrared spectroscopy (NIRS) method has been researched and developed for the simultaneous analyses of the chemical components and associated properties of mint (Mentha haplocalyx Briq.) tea samples. The common analytes were: total polysaccharide content, total flavonoid content, total phenolic content, and total antioxidant activity. To resolve the NIRS data matrix for such analyses, least squares support vector machines was found to be the best chemometrics method for prediction, although it was closely followed by the radial basis function/partial least squares model. Interestingly, the commonly used partial least squares was unsatisfactory in this case. Additionally, principal component analysis and hierarchical cluster analysis were able to distinguish the mint samples according to their four geographical provinces of origin, and this was further facilitated with the use of the chemometrics classification methods-K-nearest neighbors, linear discriminant analysis, and partial least squares discriminant analysis. In general, given the potential savings with sampling and analysis time as well as with the costs of special analytical reagents required for the standard individual methods, NIRS offered a very attractive alternative for the simultaneous analysis of mint samples.

Antioxidant activity and cytoprotective effect of kappa-carrageenan oligosaccharides and their different derivatives

Antioxidant activity of kappa-carrageenan oligosaccharides (OM) and their chemical modification derivatives was investigated employing various established in vitro systems, such as reducing power, iron ion chelation, and total antioxidant activity using beta-carotene-linoleic acid system. The oversulfated (SD), lowly (LAD), and highly acetylated derivatives (HAD) in reducing power assay, the phosphorylated derivative (PD) in metal chelating assay, and oversulfated and phosphorylated derivatives in total antioxidant activity assay exhibited antioxidant activity higher than that of carrageenan oligosaccharides. The results indicated that the chemical modification of carrageenan oligosaccharides can enhance their antioxidant activity in vitro. The protective effects of the carrageenan oligosaccharides and their chemically modified derivatives against H2O2 and UVA (long-wave ultraviolet radiation) induced oxidative damage on rat thymic lymphocyte were investigated by measuring cell viability via 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT). Thymic lymphocyte exposure to H2O2 and UVA, a marked reduction in cell survival was observed, which was significantly prevented by carrageenan oligosaccharides and their derivatives (preincubated for 2 h) at 66.7-2000 mu g/mL. But both the carrageenan oligosaccharides and their different derivatives showed the similar protective effects on intracellular level. Taken together, these results suggest that carrageenan oligosaccharides and their derivatives show relevant antioxidant activity both in vitro and in a cell system. (C) 2005 Elsevier Ltd. All rights reserved.

In vitro determination of antioxidant activity of proteins from jellyfish Rhopilema esculentum

In this study, the antioxidant activity of proteins isolated from jellyfish, Rhopilema esculentum Kishinouye (R. esculentum), was determined by various antioxidant assays, including superoxide anion radical-scavenging, hydroxyl radical-scavenging, total antioxidant activity, reducing power and metal chelating activity. Butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), alpha-tocopherol, vitamin C and mannitol were used as standards in those various antioxidant activities. The crude protein (CP) and the protein fractions isolated by Sephadex chromatography, first peak (FP) and second peak (SP), had very low reductive power and metal chelating abilities compared to EDTA, but they showed strong scavenging effects on the superoxide anion radical, hydroxyl radical and varying total antioxidant activity. FP and SP exhibited stronger scavenging effects on the superoxide anion radical than BHA, BHT or a-tocopherol. The EC50 values of FP and SP were 6.12 and 0.88 mu g/ml, respectively, while values EC50 of BHA, BHT and alpha-tocopherol were 31, 61 and 88 mu g/ml, respectively. CP, FP and SP showed far higher hydroxyl radical-scavenging activities than did vitamin C or mannitol. The EC50 values of CP, FP and SP were 48.76, 45.42 and 1.52 mu g/ml, but EC50 values of vitamin C and mannitol were 1907 and 4536 mu g/ml, respectively. In a beta-carotene-linoleate system, SP and CP showed antioxidant activity, but lower than BHA. Of the three samples, SP had the strongest antioxidant activity. So, SP may have a use as a possible supplement in the food and pharmaceutical industries. (c) 2005 Elsevier Ltd. All rights reserved.

Antioxidant activity of differently regioselective chitosan sulfates in vitro

Differently regioselective chitosan sulfates were prepared according to Hanno Baumann's methods. Their antioxidant potencies were investigated employing various established in vitro systems, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH)/superoxide/hydroxyl radicals scavenging, reducing power, iron ion chelating and total antioxidant activity. All kinds of sulfated chitosans (HCTS, TSCTS, SCTS, TCTS) showed strong inhibitory activity toward superoxide radical by the PMS-NADH system compared to Vc. According to the above-mentioned order their IC50 were 0.012, 0.040, 0.015, 0.022mg/mL, respectively, however, scavenging activity of Vc on superoxide radical was 68.19% at 2.0mg/mL. Scavenging activity of superoxide radical was found to be in the order of HCTS > SCTS > TCTS > TSCTS > Vc. Furthermore, all kinds of sulfated chitosans exhibited strong concentration-dependent inhibition of deoxyribose oxidation. Except for HCTS, others had stronger scavenging activity on hydroxyl radical than Vc. Scavenging effect of TSCTS on 1, 1 -diphenyl-2-picrylhydrazy] radical was little lower than that of BHA, but better than that of others. All kinds of sulfated chitosans were efficient in the reducing power, especially TSCTS. TSCTS and TCTS showed considerable ferrous ion chelating potency. The data obtained in vitro models clearly establish the antioxidant potency of all kinds of sulfated chitosans. These in vitro results suggested the possibility that sulfated chitosans could be effectively employed as ingredient in health or functional food, to alleviate oxidative stress. However, comprehensive studies need to be conducted to ascertain the in vivo safety of sulfated chitosans in experimental animal models. (C) 2004 Elsevier Ltd. All rights reserved.

Effect of roasting on the antioxidant activity of coffee brews

Colombian Arabica coffee beans were roasted to give light, medium, and dark samples. Their aqueous extracts were analyzed by gel filtration chromatography, UV-visible spectrophotometry, capillary electrophoresis, and the ABTS(.+) assay. A progressive decrease in antioxidant activity (associated mainly with chlorogenic acids in the green beans) with degree of roasting was observed with the simultaneous generation of high (HMM) and low molecular mass (LMM) compounds possessing antioxidant activity. Maximum antioxidant activity was observed for the medium-roasted coffee; the dark coffee had a lower antioxidant activity despite the increase in color. Analysis of the gel filtration chromatography fractions showed that the LMM fraction made a greater contribution to total antioxidant activity than the HMM components.

Changes in phenolic composition and antioxidant activity of virgin olive oil during frying

The concentration of hydroxytyrosol (3,4-DHPEA) and its secoiridoid derivatives (3,4-DHPEA-EDA and 3,4-DHPEA-EA) in virgin olive oil decreased rapidly when the oil was repeatedly used for preparing french fries in deep-fat frying operations. At the end of the first frying process (10 min at 180 degreesC), the concentration of the dihydroxyphenol components was reduced to 50-60% of the original value, and after six frying operations only about 10% of the initial components remained. However, tyrosol (p-HPEA) and its derivatives (p-HPEA-EDA and p-HPEA-EA) in the oil were much more stable during 12 frying operations. The reduction in their original concentration was much smaller than that for hydroxytyrosol and its derivatives and showed a roughly linear relationship with the number of frying operations. The antioxidant activity of the phenolic extract measured using the DPPH test rapidly diminished during the first six frying processes, from a total antioxidant activity higher than 740,mumol of Trolox/kg down to less than 250 mumol/kg. On the other hand, the concentration of polar compounds, oxidized triacylglycerol monomers (oxTGs), dimeric TGs, and polymerized TGs rapidly increased from the sixth frying operation onward, when the antioxidant activity of the phenolic extract was very low, and as a consequence the oil was much more susceptible to oxidation. The loss of antioxidant activity in the phenolic fraction due to deep-fat frying was confirmed by the storage oil and oil-in-water emulsions containing added extracts from olive oil used for 12 frying operations.

Antioxidant Activity of Commercial Ready-to-Drink Orange Juice and Nectar

Total antioxidant activity (TAA), total phenolic compounds (TPC), and physicochemical characteristics of ready-to-drink orange juice and nectar from the most consumed brands available in Brazil were evaluated. TPC ranged from 18.7 to 54.2 mg of gallic acid/100 mL, and TAA varied from 57.88 to 349.32 mu mol TEAC/100 mL ready-to-drink orange juice and nectar. The ascorbic acid content was the only physicochemical parameter that showed strong variation among packages and brands. Correlation of TPC with TAA showed that the higher the level of TPC the higher the TAA. Correlation of ascorbic acid content with TAA is higher for ready-to-drink orange juice than nectar. The same was found for the correlation of ascorbic acid content with TPC. The results confirm the contribution of the TPC to TAA.

Validation of an alternative analytical method for the quantification of antioxidant activity in plant extracts

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Validation of an alternative analitycal method for the quantification of antioxidant activity in plant extracts

SUMMARY. A new method was developed to evaluate the total antioxidant activity in plant extracts, which was based on radical scavenging using 2,2’-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid. The proposed method was linear in the range of 0.86 to 26.0 μg/mL, displaying a correlation coefficient of 0.999. Moreover, the accuracy and precision analysis showed agreement with ANVISA guidelines (96.66 to 98.46 % and < 5.0%, respectively). The method demonstrated sensitivity, robustness and efficiency in detecting low concentrations of plant extracts (detection and quantification limit of 0.86 and 2.87 μg/mL, respectively) that may be present in pharmaceuticals and cosmetics preparations, again in agreement with ANVISA. In addition, the assay is inexpensive and easy to perform.

Antioxidant Activity and Total Phenols from the Methanolic Extract of Miconia albicans (Sw.) Triana Leaves

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Antioxidant activity, ascorbic acid and total phenol of exotic fruits occurring in Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)