Antioxidant capacity of different broccoli (Brassica oleracea) genotypes using the oxygen radical absorbance capacity (ORAC) assay

Antioxidant capacity of hydrophilic and lipophilic extracts from eight broccoli genotypes was compared using the oxygen radical absorbance capacity (ORAC) assay. Each genotype was analyzed for carotenoid, tocopherol, ascorbic acid, and flavonoid content. Results indicate that the antioxidant capacity of hydrophilic extracts ranged from 65.8 to 121.6 micromol trolox equivalents (TE)/g of tissue, and the capacity of lipophilic extracts ranged from 3.9 to 17.5 micromol TE/g. Ascorbic acid and flavonoid content of the hydrophilic extracts did not explain the total variation in antioxidant capacity of those extracts, suggesting either the presence of other antioxidant components that have yet to be identified or that the known antioxidants are producing synergistic effects. The carotenoids did correlate with antioxidant capacity of the lipophilic extracts and accounted for the majority of the variability in that fraction. The variability in hydrophilic and lipophilic antioxidant capacity found among these genotypes suggests that potential efficacy from antioxidants will vary considerably from genotype to genotype.     

Assays for hydrophilic and lipophilic antioxidant capacity (oxygen radical absorbance capacity (ORAC(FL))) of plasma and other biological and food samples

Methods are described for the extraction and analysis of hydrophilic and lipophilic antioxidants, using modifications of the oxygen radical absorbing capacity (ORAC(FL)) procedure. These methods provide, for the first time, the ability to obtain a measure of "total antioxidant capacity" in the protein free plasma, using the same peroxyl radical generator for both lipophilic and hydrophilic antioxidants. Separation of the lipophilic and hydrophilic antioxidant fractions from plasma was accomplished by extracting with hexane after adding water and ethanol to the plasma (hexane/plasma/ethanol/water, 4:1:2:1, v/v). Lipophilic and hydrophilic antioxidants were efficiently partitioned between hexane and aqueous solvents. Conditions for controlling temperature effects and decreasing assay variability using fluorescein as the fluorescent probe were validated in different laboratories. Incubation (37 degrees C for at least 30 min) of the buffer to which AAPH was dissolved was critical in decreasing assay variability. Lipophilic antioxidants represented 33.1 +/- 1.5 and 38.2 +/- 1.9% of the total antioxidant capacity of the protein free plasma in two independent studies of 6 and 10 subjects, respectively. Methods are described for application of the assay techniques to other types of biological and food samples.     

Phytochemicals and antioxidant activity of milled fractions of different wheat varieties

The health-promoting effects of whole-grain consumption have been attributed in part to their unique phytochemical contents and profiles that complement those found in fruits and vegetables. Wheat is an important component of the human diet; however, little is known about the phytochemical profiles and total antioxidant activities of milled fractions of different wheat varieties. The objectives of this study were to investigate the distribution of phytochemicals (total phenolics, flavonoids, ferulic acid, and carotenoids) and to determine hydrophilic and lipophilic antioxidant activity in milled fractions (endosperm and bran/germ) of three different wheat varieties, two of which were grown in two environments. Grain samples of each of the wheat varieties were milled into endosperm and bran/germ fractions. Each fraction was extracted and analyzed for total phenolics, ferulic acid, flavonoids, carotenoid contents, and hydrophilic and lipophilic antioxidant activities. Total phenolic content of bran/germ fractions (2867-3120 micromol of gallic acid equiv/100 g) was 15-18-fold higher (p < 0.01) than that of respective endosperm fractions. Ferulic acid content ranged from 1005 to 1130 micromol/100 g in bran/germ fractions and from 15 to 21 micromol/100 g in the endosperm fractions. The bran/germ fraction flavonoid content was 740-940 micromol of catechin equiv/100 g. On average, bran/germ fractions of wheat had 4-fold more lutein, 12-fold more zeaxanthin, and 2-fold more beta-cryptoxanthin than the endosperm fractions. Hydrophilic antioxidant activity of bran/germ samples (7.1-16.4 micromol of vitamin C equiv/g) was 13-27-fold higher than that of the respective endosperm samples. Similarly, lipophilic antioxidant activity was 28-89-fold higher in the bran/germ fractions (1785-4669 nmol of vitamin E equiv/g). Hydrophilic antioxidant activity contribution to the total antioxidant activity (hydrophilic + lipophilic) was >80%. In whole-wheat flour, the bran/germ fraction contributed 83% of the total phenolic content, 79% of the total flavonoid content, 51% of the total lutein, 78% of the total zeaxanthin, 42% of the total beta-cryptoxanthin, 85% of the total hydrophilic antioxidant activity, and 94% of the total lipophilic antioxidant activity. Our results showed that different milled fractions of wheat have different profiles of both hydrophilic and lipophilic phytochemicals. These findings provide information necessary for evaluating contributions to good health and disease prevention from whole-wheat consumption.     

Optimization of the extraction of antioxidative constituents of six barley cultivars and their antioxidant properties

Response surface methodology (RSM) was used to predict the optimum conditions of extraction of barley samples (organic solvent percent in the extraction medium, temperature, and time). Antioxidant capacity in the barley meals was highest under optimum extraction conditions of 80.2% methanol and 60.5 degrees C for 38.36 min as predicted by RSM. Phenolic antioxidative compounds of six barley cultivars, namely, Falcon, AC Metcalfe, Tercel, Tyto, Phoenix, and Peregrine, were extracted under the conditions obtained by RSM after defatting with hexane, and subsequently the extracts were assessed for their antioxidant and antiradical activities and metal chelation efficacy. The potential of barley extracts in inhibiting peroxyl and hydroxyl radical induced supercoiled DNA double-strand scission was also studied. Total phenolic content as measured according to Folin-Ciocalteu's method ranged from 13.58 to 22.93 mg of ferulic acid equiv/g of defatted material, with the highest content in Peregrine. Total antioxidant activity as measured by Trolox equivalent antioxidant capacity ranged from 3.74 to 6.82 micromol/g of defatted material. Metal chelation capacity of the extracts as measured by 2,2'-bipyridyl competition assay varied from 1.1 to 2.1 micromol of ethylenediaminetetraacetic acid equiv/g of defatted material. IC(50) values for 1,1-diphenyl-2-picrylhydrazyl radical as measured by electron paramagnetic resonance ranged from 1.51 to 3.33 mg/mL, whereas the corresponding values for hydroxyl radical ranged between 2.20 and 9.65 mg/mL. Inhibition of peroxyl radical induced supercoiled DNA scission ranged from 78.2 to 92.1% at the concentration of 4 mg/mL of extracts, whereas the corresponding values for hydroxyl radical induced DNA scission ranged from 53.1 to 65.3%.     

Development and validation of oxygen radical absorbance capacity assay for lipophilic antioxidants using randomly methylated beta-cyclodextrin as the solubility enhancer

We recently reported the improved oxygen radical absorbance capacity (ORAC) assay using fluorescein (FL) as the fluorescent probe. The current ORAC(FL) assay is limited in hydrophilic antioxidant due to the aqueous environment of the assay. Lipophilic antioxidants mainly include the vitamin E family and carotenoids, which play a critical role in biological defense systems. In this paper, we expanded the current ORAC(FL) assay to lipophilic antioxidants. Randomly methylated beta-cyclodextrin (RMCD) was introduced as the water solubility enhancer for lipophilic antioxidants. Seven percent RMCD (w/v) in a 50% acetone-H(2)O mixture was found to sufficiently solubilize vitamin E compounds and other lipophilic phenolic antioxidants in 75 mM phosphate buffer (pH 7.4). This newly developed ORAC assay (abbbreviated ORAC(FL-LIPO)) was validated through linearity, precision, accuracy, and ruggedness. The validation results demonstrate that the ORAC(FL-LIPO) assay is reliable and robust. For the first time, by using 6-hydroxy-2,5,7,8-tetramethyl-2-carboxylic acid as a standard (1.0), the ORAC values of alpha-tocopherol, (+)-gamma-tocopherol, (+)-delta-tocopherol, alpha-tocopherol acetate, tocotrienols, 2,6-di-tert-butyl-4-methylphenol, and gamma-oryzanol were determined to be 0.5 +/- 0.02, 0.74 +/- 0.03, 1.36 +/- 0.14, 0.00, 0.91 +/- 0.04, 0.16 +/- 0.01, and 3.00 +/- 0.26, respectively. The structural information of oxidized alpha-tocopherol obtained by liquid chromatography/mass spectrometry reveals that the mechanism for the reaction between the vitamin E and the peroxyl radical follows the hydrogen atom transfer mechanism, which is in agreement with the notion that vitamin E is the chain-breaking antioxidant.     

High-throughput relative DPPH radical scavenging capacity assay

A high-throughput relative 2,2-diphenyl-1-picryhydrazyl (DPPH) radical scavenging capacity (RDSC) assay was developed and validated in the present study. This RDSC assay is easy to perform and has acceptable accuracy (90-110% recovery), precision [3.9-7.0% pooled relative standard deviation (RSD)], and reproducibility (2.2 and 3.5% interday and intraday RSD). This assay reports the RDSC values for antioxidant samples, which make it possible to compare the DPPH radical scavenging capacities of antioxidants determined in different laboratories. The RDSC assay may be conducted in aqueous alcohol and acetone for hydrophilic antioxidants or in the organic solvents for lipophilic antioxidants without solubilizing agents, which makes it possible to directly compare the radical scavenging capacities of hydrophilic and lipophilic antioxidants. In addition, the high-throughput RDSC assay could be utilized for EC50 value estimation. The high-throughput RDSC assay may be used for screening and investigating potential natural antioxidants.     

Determination of free flavan-3-ol content in barley (Hordeum vulgare L.) air-classified flours: comparative study of HPLC-DAD/MS and spectrophotometric determinations

The determination of free flavan-3-ol compounds in barley flours (cv. Gotic) and two resulting milling fractions (fine fraction 57% and coarse fraction 43%, w/w) obtained by air classification of dehulled grain is herein described. The determinations were carried out using reversed phase high-performance liquid chromatography coupled with both diode array detection and ESI-MS compared with conventional spectrophotometric determinations (total phenolic compounds by the Folin-Ciocalteu method and free radical scavenging activity with the DPPH assay). Significant correlations among the HPLC quantification, the spectrophotometric data, and the antioxidant capacity of extracts were revealed by Pearson's analysis. Nine flavan-3-ols were identified by HPLC-MS. Catechins and their derivatives were found to make a substantial contribution to the antioxidant power of extracts. The coarse fraction showed larger concentrations of flavan-3-ols (221%) with respect to the fine fraction. This was confirmed by the antioxidant activity of the analyzed flours. The coarse fraction showed the greatest antioxidant activity (1200.1 +/- 66.2 micromol of Trolox equiv/100 g of flour) with respect to whole meal and fine fraction (1025.9 +/- 18.3 and 761.7 +/- 55.3 micromol of Trolox equiv/100 g of flour, respectively).     

Lipophilic and hydrophilic antioxidant capacities of common foods in the United States

Both lipophilic and hydrophilic antioxidant capacities were determined using the oxygen radical absorbance capacity (ORAC(FL)) assay with fluorescein as the fluorescent probe and 2,2'-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator on over 100 different kinds of foods, including fruits, vegetables, nuts, dried fruits, spices, cereals, infant, and other foods. Most of the foods were collected from four different regions and during two different seasons in U.S. markets. Total phenolics of each sample were also measured using the Folin-Ciocalteu reagent. Hydrophilic ORAC(FL) values (H-ORAC(FL)) ranged from 0.87 to 2641 micromol of Trolox equivalents (TE)/g among all of the foods, whereas lipophilic ORAC(FL) values (L-ORAC(FL)) ranged from 0.07 to 1611 micromol of TE/g. Generally, L-ORAC(FL) values were <10% of the H-ORAC(FL) values except for a very few samples. Total antioxidant capacity was calculated by combining L-ORAC(FL) and H-ORAC(FL). Differences of ORAC(FL) values in fruits and vegetables from different seasons and regions were relatively large for some foods but could not be analyzed in detail because of the sampling scheme. Two different processing methods, cooking and peeling, were used on selected foods to evaluate the impact of processing on ORAC(FL). The data demonstrated that processing can have significant effects on ORAC(FL). Considering all of the foods analyzed, the relationship between TP and H-ORAC(FL) showed a very weak correlation. Total hydrophilic and lipophilic antioxidant capacity intakes were calculated to be 5558 and 166 micromol of TE/day, respectively, on the basis of data from the USDA Continuing Survey of Food Intakes by Individuals (1994-1996).     

Antioxidant and antiproliferative activities of Spirulina and Chlorella water extracts

Liver fibrosis is a chronic liver disease that will further develop to cirrhosis if severe damage continues to form. A potential treatment for liver fibrosis is to inhibit activated hepatic stellate cell (HSC) proliferation and, subsequently, to induce HSC apoptosis. It has been reported that antioxidants are able to inhibit the proliferation of HSCs. In this study, the aqueous extract of spirulina was chosen as the source of antioxidant to investigate the inhibitory effect on the proliferation of HSC. The growth inhibitory effects of aqueous spirulina and chlorella extract on human liver cancer cells, HepG2, were also studied and compared in pairs. Results indicated that the total phenol content of spirulina was almost five times greater than that of chlorella (6.86 +/- 0.58 vs 1.44 +/- 0.04 mg tannic acid equivalent/g of algae powder, respectively). The antioxidant activity of spirulina determined by the ABTS*+ method was higher than chlorella (EC50: 72.44 +/- 0.24 micromol of trolox equivalent/g of spirulina extract vs 56.09 +/- 1.99 micromol of trolox equivalent/g of chlorella extract). Results of DPPH* assay also showed a similar trend as the ABTS*+ assay (EC50: 19.39 +/- 0.65 micromol of ascorbic acid equivalent/g of spirulina extract vs 14.04 +/- 1.06 micromol of ascorbic acid equivalent/g of chlorella extract). The aqueous extracts of these two algae both showed antiproliferative effects on HSC and HepG2, but spirulina was a stronger inhibitor than chlorella. Annexin-V staining showed that aqueous extract of spirulina induced apoptosis of HSC after 12 h of treatment. In addition, the aqueous extract of spirulina triggered a cell cycle arrest of HSC at the G2/M phase.     

Phytochemical quantification and total antioxidant capacities of emmer (Triticum dicoccon Schrank) and einkorn (Triticum monococcum L.) wheat landraces

In this study, samples of 18 ancient wheat (12 emmer, 6 einkorn) and 2 bread wheat varieties grown in different regions of Turkey were examined for their total phenolics and flavonoids, phenolic acids, lutein, total yellow pigment, and total radical scavenging capacities against ABTS cation. Results showed that health beneficial phytochemicals and total antioxidant capacities were generally significantly different in emmer and einkorn wheat groups. Remarkably higher total antioxidant activity (18.31 +/- 1.31 micromol Trolox equiv/g), total phenolics (6.33 +/- 0.98 micromol gallic acid equiv/g), ferulic acid (662.95 +/- 61.07 microg/g), and flavonoids (1.61 +/- 0.34 micromol catechin equiv/g) content were detected in emmer wheat samples (n = 12), suggesting that they may have high potential for utilization as a novel grain, rich in natural antioxidants. In addition, quite high levels of lutein (7.33 +/- 2.43 microg/g) of einkorn samples (n = 6) hold the potential of developing high-lutein bakery products to considerably raise the dietary intake of carotenoids. These findings for ancient wheat varieties are considered to be very useful in breeding programs for selecting and breeding wheat varieties for higher concentration and better composition of health-beneficial phytochemicals.     

Procyanidin and catechin contents and antioxidant capacity of cocoa and chocolate products

Cocoa and chocolate products from major brands were analyzed blind for total antioxidant capacity (AOC) (lipophilic and hydrophilic ORAC(FL)), catechins, and procyanidins (monomer through polymers). Accuracy of analyses was ascertained by comparing analyses on a NIST standard reference chocolate with NIST certified values. Procyanidin (PC) content was related to the nonfat cocoa solid (NFCS) content. The natural cocoa powders (average 87% of NFCS) contained the highest levels of AOC (826 +/- 103 micromol of TE/g) and PCs (40.8 +/- 8.3 mg/g). Alkalized cocoa (Dutched powders, average 80% NFCS) contained lower AOC (402 +/- 6 micromol of TE /g) and PCs (8.9 +/- 2.7 mg/g). Unsweetened chocolates or chocolate liquor (50% NFCS) contained 496 +/- 40 micromol of TE /g of AOC and 22.3 +/- 2.9 mg/g of PCs. Milk chocolates, which contain the least amount of NFCS (7.1%), had the lowest concentrations of AOC (80 +/- 10 micromol of TE /g) and PCs (2.7 +/- 0.5 mg/g). One serving of cocoa (5 g) or chocolate (15 or 40 g, depending upon the type of chocolate) provides 2000-9100 micromol of TE of AOC and 45-517 mg of PCs, amounts that exceed the amount in a serving of the majority of foods consumed in America. The monomers through trimers, which are thought to be directly bioavailable, contributed 30% of the total PCs in chocolates. Hydrophilic antioxidant capacity contributed >90% of AOC in all products. The correlation coefficient between AOC and PCs in chocolates was 0.92, suggesting that PCs are the dominant antioxidants in cocoa and chocolates. These results indicate that NFCS is correlated with AOC and PC in cocoa and chocolate products. Alkalizing dramatically decreased both the procyanidin content and antioxidant capacity, although not to the same extent.     

Antioxidant activity of grains

Epidemiological studies have shown that consumption of whole grains and grain-based products is associated with reduced risk of chronic diseases. The health benefits of whole grains are attributed in part to their unique phytochemical composition. However, the phytochemical contents in grains have been commonly underestimated in the literature, because bound phytochemicals were not included. This study was designed to investigate the complete phytochemical profiles in free, soluble conjugated, and insoluble bound forms, as well as their antioxidant activities in uncooked whole grains. Corn had the highest total phenolic content (15.55 +/- 0.60 micromol of gallic acid equiv/g of grain) of the grains tested, followed by wheat (7.99 +/- 0.39 micromol of gallic acid equiv/g of grain), oats (6.53 +/- 0.19 micromol of gallic acid equiv/g of grain), and rice (5.56 +/- 0.17 micromol of gallic acid equiv/g of grain). The major portion of phenolics in grains existed in the bound form (85% in corn, 75% in oats and wheat, and 62% in rice), although free phenolics were frequently reported in the literature. Ferulic acid was the major phenolic compound in grains tested, with free, soluble-conjugated, and bound ferulic acids present in the ratio 0.1:1:100. Corn had the highest total antioxidant activity (181.42 +/- 0.86 micromol of vitamin C equiv/g of grain), followed by wheat (76.70 +/- 1.38 micromol of vitamin C equiv/g of grain), oats (74.67 +/- 1.49 micromol of vitamin C equiv/g of grain), and rice (55.77 +/- 1.62 micromol of vitamin C equiv/g of grain). Bound phytochemicals were the major contributors to the total antioxidant activity: 90% in wheat, 87% in corn, 71% in rice, and 58% in oats. Bound phytochemicals could survive stomach and intestinal digestion to reach the colon. This may partly explain the mechanism of grain consumption in the prevention of colon cancer, other digestive cancers, breast cancer, and prostate cancer, which is supported by epidemiological studies.     

Bioactive components of caper (Capparis spinosa L.) from Sicily and antioxidant effects in a red meat simulated gastric digestion

An increasing body of evidence on the association between adherence to the Mediterranean diet and healthy status is being accumulated. Floral buds of Capparis spinosa L. are commonly used in the Mediterranean cuisine as flavoring for meat and other foods. The present study evaluated bioactive components and antioxidant activity of Sicilian capers stabilized in salt. Whereas alpha-tocopherol was absent, low levels of gamma-tocopherol and vitamin C were measured. With reference to one serving size (8.6 g of capers), rutin was 13.76 mg, isothiocyanates, recently acknowledged as anticarcinogen phytochemicals, were 42.14 micromol, total phenols were 4.19 mg of gallic acid equivalents (GAE), and the total antioxidant potential measured using the [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] diammonium salt (ABTS) cation radical decolorization assay was 25.8 micromol of Trolox equivalents. The antioxidative activity of a caper hydrophilic extract was assessed in a number of assays. The extract at 3.5 and 7.0 microM GAE exhibited a dose-dependent peroxyl radical scavenging activity in a methyl linoleate methanol solution oxidized by azo initiator, and reduced hypervalent iron myoglobin species formed from met-Mb an H 2O 2, at 180 microM GAE. The hydrophilic extract, at 70-280 microM GAE, caused a dose-dependent inhibition of lipid autoxidation in heated red meat, incubated with simulated gastric fluid for 180 min. In the same model rutin tested at a concentration corresponding to its content in the extract was ineffective, and alpha-tocopherol at 25 microM was poorly effective. The hydrophilic extract (70 microM GAE) prevented the consumption of the co-incubated alpha-tocopherol, whereas lipid oxidation was inhibited for the experimental time, suggesting cooperative interactions between extract components and the vitamin. The findings encourage the use of caper with foods that contribute oxidizable lipids in view of the association between dietary oxidized lipids and risk of oxidative stress-based diseases.     

Correlation analyses of phytochemical composition, chemical, and cellular measures of antioxidant activity of broccoli (Brassica oleracea L. Var. italica)

Chemical measures of antioxidant activity within the plant, such as the oxygen radical absorbance capacity (ORAC) assay, have been reported for many plant-based foods. However, the extent to which chemical measures relate to cellular measures of oxidative stress is unclear. The natural variation in the phytochemical content of 22 broccoli genotypes was used to determine correlations among chemical composition (carotenoids, tocopherols and polyphenolics), chemical antioxidant activity (ORAC), and measures of cellular antioxidation [prevention of DNA oxidative damage and of oxidation of the biomarker dichlorofluorescein (DCFH) in HepG2 cells] using hydrophilic and lipophilic extracts of broccoli. For lipophilic extracts, ORAC (ORAC-L) correlated with inhibition of cellular oxidation of DCFH (DCFH-L, r = 0.596, p = 0.006). Also, DNA damage in the presence of the lipophilic extract was negatively correlated with both chemical and cellular measures of antioxidant activity as measured by ORAC-L (r = -0.705, p = 0.015) and DCFH-L (r = -0.671, p = 0.048), respectively. However, no correlations were observed for hydrophilic (-H) extracts, except between polyphenol content and ORAC (ORAC-H; r = 0.778, p < 0.001). Inhibition of cellular oxidation by hydrophilic extracts (DCFH-H) and ORAC-H were approximately 8- and 4-fold greater than DCFH-L and ORAC-L, respectively. Whether ORAC-H has more biological relevance than ORAC-L because of its magnitude or whether ORAC-L bears more biological relevance because it relates to cellular estimates of antioxidant activity remains to be determined. Chemical estimates of antioxidant capacity within the plant may not accurately reflect the complex nature of the full antioxidant activity of broccoli extracts within cells.     

Comparison of antioxidant activity, anthocyanins, carotenoids, and phenolics of three native fresh and sun-dried date (Phoenix dactylifera L.) varieties grown in Oman

Fresh and sun-dried dates of three native varieties from Oman, namely, Fard, Khasab, and Khalas, were examined for their antioxidant activity and total contents of anthocyanins, carotenoids, and phenolics, as well as free and bound phenolic acids. All results are expressed as mean value +/- standard deviation (n = 3) on a fresh weight basis. Fresh date varieties were found to be a good source of antioxidants (11687-20604 micromol of Trolox equiv/g), total contents of anthocyanins (0.24-1.52 mg of cyanidin 3-glucoside equiv/100 g), carotenoids (1.31-3.03 mg/100 g), phenolics (134-280 mg of ferulic acid equiv/100 g), free phenolic acids (2.61-12.27 mg/100 g), and bound phenolic acids (6.84-30.25 mg/100 g). A significant (p < 0.05) amount of antioxidants and carotenoids was lost after sun-drying of dates, whereas the total content of phenolics and free and bound phenolic acids increased significantly (p < 0.05). Anthocyanins were detected only in fresh dates. Date varieties had different levels and patterns of phenolic acids. Four free phenolic acids (protocatechuic acid, vanillic acid, syringic acid, and ferulic acid) and nine bound phenolic acids (gallic acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, and o-coumaric acid) were tentatively identified. Of the date varieties studied, Khalas, which is considered to be premium quality, had higher antioxidant activity, total carotenoids, and bound phenolic acids than other varieties. These results suggest that all date varieties serve as a good source of natural antioxidants and could potentially be considered as a functional food or functional food ingredient, although some of their antioxidant constituents are lost during sun-drying.     

Effect of foliar application of selenium on the antioxidant activity of aqueous and ethanolic extracts of selenium-enriched rice

Selenium fertilizer was foliar applied to determine the effects of antioxidant activity of selenium-enriched rice assessed by alpha,alpha-diphenyl-beta-picylhydrazyl (DPPH) radical scavenging and the ferric thiocyanate (FTC) method. Results showed that selenium concentration in rice was significantly enhanced dose dependently. Aqueous or ethanolic extracts of rice displayed significantly higher antioxidant activity against lipid peroxidation. The activities of aqueous extracts were significantly higher than those of ethanolic extracts and increased with the increasing selenium concentration in rice. The DPPH assay showed that the kinetic behaviors of aqueous extracts were complex and slow, while ethanolic extracts reacted quickly with DPPH radical. Aqueous extracts of rice exhibited higher antiradical efficiencies than ethanolic extracts, and rice (1.275 mg Se kg(-)(1)) presented the lowest EC(50) values of 533.46 +/- 0.58 microg mL(-)(1). As compared to rice extracts, all of the reference antioxidants showed more than 4-fold antiradical efficiencies than rice extracts. This radical scavenging activity was significantly correlated with selenium concentrations in rice (R = 0.862, p < 0.05), while ethanolic extracts were inversely correlated with selenium concentration in rice.     

Novel low-density lipoprotein (LDL) oxidation model: antioxidant capacity for the inhibition of LDL oxidation

A novel model of peroxyl radical initiated low-density lipoprotein (LDL) oxidation (LDL oxidation model for antioxidant capacity, or LOMAC) was developed to assess the free radical scavenging capacity of antioxidants and the extracts of natural products. A water-soluble free radical initiator, 2,2'-azobis(amidinopropane) dihydrochloride, was used at physiological temperature (37 degrees C) to generate peroxyl radicals to catalyze lipid oxidation of LDL isolated from human plasma samples. Headspace hexanal, a major decomposition product of LDL oxidation, was measured by a headspace gas chromatograph as an indicator of antioxidant capacity of different concentrations of pure antioxidants (vitamins C and E) and the extracts of natural products (fresh apple phytochemical extracts). All vitamin C and E and apple extract concentrations tested resulted in increasing partial suppression and delay of LDL oxidation. On the basis of the median effective dose (EC(50)) calculated for each compound or extract tested, the LOMAC value of 100 g of apple against LDL oxidation was equivalent to 1470 mg of vitamin E or to 402 mg of vitamin C. This study shows that the LOMAC assay can be routinely used to analyze or screen antioxidants or phytochemical extracts against LDL oxidation to prevent cardiovascular disease. The food-specific LOMAC values will be very useful as a new alternative biomarker for future epidemiological studies of cardiovascular disease.     

Antioxidant compounds and antioxidant activity in "early potatoes"

The antioxidant content and the antioxidant capacity of both hydrophilic and lipophilic antioxidant extracts from four "early potato" cultivars, grown in two different locations (Racale and Monteroni), were examined. There was a considerable variation in carotenoid content and weak differences in the ascorbic acid concentration of the examined cultivars of "early potato" and between the harvested locations. An increase in both methanol/water (8:2 v/v) and phosphate buffer soluble (PBS) free phenols (70%) and bound phenols (28%) in the extracts from the cultivars grown at Racale site was found and discussed. Examination of individual phenols revealed that chlorogenic acid and catechin were the major phenols present in potato tuber extracts; a moderate amount of caffeic acid and ferulic acid was also detected. The total equivalent antioxidant capacity (TEAC) was higher in the Racale extracts and a highly positive linear relationship ( R (2) = 0.8193) between TEAC values and total phenolic content was observed. The oxyradical scavenging capacity (TOSC) of methanol/water and PBS extracts of peel and whole potatoes against the reactive oxygen species (ROS) peroxyl radicals, peroxynitrite, and hydroxyl radicals was also analyzed. A highly significant linear correlation ( R (2) = 0.9613) between total antioxidant capacity (as a sum of peroxyl radicals + peroxynitrite) and total phenol content of methanol/water extracts was established. Moreover, proliferation of human mammalian cancer (MCF-7) cells was significantly inhibited in a dose-dependent manner after exposure to potato extracts. These data can be useful for "early potato" tuber characterization and suggest that the "early potato" has a potential as a dietary source of antioxidants.     

High-amylose corn exhibits better antioxidant activity than typical and waxy genotypes

The consumption of fruits, vegetables, and whole grains rich in antioxidative phytochemicals is associated with a reduced risk of chronic diseases such as cancer, coronary heart disease, diabetes, Alzheimer's disease, cataract, and aged-related functional decline. For example, phenolic acids are among the main antioxidative phytochemicals in grains that have been shown to be beneficial to human health. Corn (Zea mays L.) is a major staple food in several parts of the world; thus, the antioxidant activity of several corn types was evaluated. The 2,2-Diphenyl-1-picryhydrazyl free radical (DPPH*) scavenging activity, total phenolic content (TPC), antioxidant capacity of lipid-soluble substances (ACL), oxygen radical absorbance capacity (ORAC), and phenolic acid compositions of typical and mutant genotypes (typical-1, waxy, typical-2, and high-amylose) were investigated. The DPPH* scavenging activity at 60 min was 34.39-44.51% in methanol extracts and 60.41-67.26% in HCl/methanol (1/99, v/v) extracts of corn. The DPPH* scavenging activity of alkaline hydrolysates of corn ranged from 48.63 to 64.85%. The TPC ranged from 0.67 to 1.02 g and from 0.91 to 2.15 g of ferulic acid equiv/kg of corn in methanol and HCl/methanol extracts, respectively. The TPC of alkaline hydrolysates ranged from 2.74 to 6.27 g of ferulic acid equiv/kg of corn. The ACL values were 0.41-0.80 and 0.84-1.59 g of Trolox equiv/kg of corn in methanol and HCl/methanol extracts, respectively. The ORAC values were 10.57-12.47 and 18.76-24.92 g of Trolox equiv/kg of corn in methanol and HCl/methanol extracts, respectively. ORAC values of alkaline hydrolysates ranged from 42.85 to 68.31 g of Trolox equiv/kg of corn. The composition of phenolic acids in alkaline hydrolysates of corn was p-hydroxybenzoic acid (5.08-10.6 mg/kg), vanillic acid (3.25-14.71 mg/kg), caffeic acid (2.32-25.73 mg/kg), syringic acid (12.37-24.48 mg/kg), p-coumaric acid (97.87-211.03 mg/kg), ferulic acid (1552.48-2969.10 mg/kg), and o-coumaric acid (126.53-575.87 mg/kg). Levels of DPPH* scavenging activity, TPC, ACL, and ORAC in HCl/methanol extracts were obviously higher than those present in methanol extracts. There was no significant loss of antioxidant capacity when corn was dried at relatively high temperatures (65 and 93 degrees C) postharvest as compared to drying at ambient temperatures (27 degrees C). Alkaline hydrolysates showed very high TPC, ACL, and ORAC values when compared to methanol and HCl/methanol extracts. High-amylose corn had a better antioxidant capacity than did typical (nonmutant) corn genotypes.     

Cellular antioxidant activity (CAA) assay for assessing antioxidants, foods, and dietary supplements

A cellular antioxidant activity (CAA) assay for quantifying the antioxidant activity of phytochemicals, food extracts, and dietary supplements has been developed. Dichlorofluorescin is a probe that is trapped within cells and is easily oxidized to fluorescent dichlorofluorescein (DCF). The method measures the ability of compounds to prevent the formation of DCF by 2,2'-azobis(2-amidinopropane) dihydrochloride (ABAP)-generated peroxyl radicals in human hepatocarcinoma HepG2 cells. The decrease in cellular fluorescence when compared to the control cells indicates the antioxidant capacity of the compounds. The antioxidant activities of selected phytochemicals and fruit extracts were evaluated using the CAA assay, and the results were expressed in micromoles of quercetin equivalents per 100 micromol of phytochemical or micromoles of quercetin equivalents per 100 g of fresh fruit. Quercetin had the highest CAA value, followed by kaempferol, epigallocatechin gallate (EGCG), myricetin, and luteolin among the pure compounds tested. Among the selected fruits tested, blueberry had the highest CAA value, followed by cranberry > apple = red grape > green grape. The CAA assay is a more biologically relevant method than the popular chemistry antioxidant activity assays because it accounts for some aspects of uptake, metabolism, and location of antioxidant compounds within cells.