Evaluation of antioxidant activity and preventing DNA damage effect of pomegranate extracts by chemiluminescence method

The antioxidant activities of three parts (peel, juice, and seed) and extracts of three pomegranate varieties in China were investigated by using a chemiluminescence (CL) method in vitro. The scavenging ability of pomegranate extracts (PEs) on superoxide anion, hydroxide radical, and hydrogen peroxide was determined by the pyrogallol-luminol system, the CuSO4-Phen-Vc-H2O2 system, and the luminol-H2O2 system, respectively. DNA damage preventing the effect of PE was determined by the CuSO4-Phen-Vc-H2O2-DNA CL system. The results showed that the peel extract of red pomegranate had the best effect on the scavenging ability of superoxide anion because its IC50 value (4.01 +/- 0.09 microg/mL) was the lowest in all PEs. The seed extract of white pomegranate could scavenge hydroxide radical most effectively of the nine extracts (the IC50 value was 1.69 +/- 0.03 microg/mL). The peel extract of white pomegranate had the best scavenging ability on hydrogen peroxide, which had the lowest IC50 value (0.032 +/- 0.003 microg/mL) in the nine extracts. The seed extract of white pomegranate (the IC50 value was 3.67 +/- 0.03 microg/mL) was the most powerful on the DNA damage-preventing effect in all of the PEs. Also, the statistical analysis indicated that there were significant differences (at P < 0.05) among the extracts of the different varieties and parts in each system.     

Variation in major antioxidants and total antioxidant activity of Yuzu (Citrus junos Sieb ex Tanaka) during maturation and between cultivars

Epidemiological studies suggest that a high consumption of fruits can reduce the risk of some cancers and cardiovascular disease, and this may be attributable to the antioxidant activity of vitamins and phenolic compounds. The present study investigated the variations in vitamin C, total phenolic, hesperidin, and naringin contents, and total antioxidant activity of yuzu (Citrus junos Sieb ex Tanaka)-which is a popular citrus fruit in Korea and Japan-between cultivars and during maturity. The amounts of phenolics and vitamin C and the antioxidant activity in all tested yuzu cultivars were higher in peel than in flesh. Ripening increased the total antioxidant activity and vitamin C content in both peel and flesh of yuzu. However, the amounts of all total phenolics, hesperidin, and naringin in peel increased with ripening, whereas they decreased slightly in flesh. There was a highly linear relationship between the vitamin C content and the total antioxidant activity in both peel (r(2) = 1.000) and flesh (r(2) =0.998), suggesting that vitamin C plays a key role in the antioxidant activity of yuzu. In addition, the contribution of each antioxidant to the total antioxidant activity of yuzu was determined using a 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging assay and is expressed here in terms of the vitamin C equivalent antioxidant capacity (VCEAC). The means of vitamin C, naringin, and hesperidin in yuzu were 90.4, 63.8, and 65.7 mg/100 g fresh yuzu, respectively. The relative VCEAC values of these compounds were in the following order: vitamin C (1.00) > naringin (0.195) > hesperidin (0.162). Therefore, the estimated contribution of each antioxidant to the total antioxidant capacity of 100 g of fresh yuzus is as follows (in mg of VCEAC): vitamin C (90.36 mg) > naringin (12.44 mg) > hesperidin (10.64 mg). Our results indicate that mature yuzu contains higher amounts of vitamin C and phenolics than other citrus fruits and could therefore be used as a significant dietary source of antioxidants.     

Differences in the carotenoid content of ordinary citrus and lycopene-accumulating mutants

High-performance liquid chromatography, coupled with photodiode array detection, was used to analyze the carotenoid composition of peel and juice vesicle tissues of ordinary and lycopene-accumulating mutants (referred to as red mutants in this article) of orange, pummelo, and grapefruit. Thirty-six major carotenoids, including some cis-trans isomers, were separated on a C30 reversed phase column, and 23 of them were identified on the basis of retention times and spectral characteristics with authentic standards. Carotenoid profiles varied with tissue types, citrus species, and mutations. beta-Citraurin occurred in the peel of oranges but not in juice vesicles, whereas the reverse was found for violaxanthin, 9-cis-violaxanthin, and luteoxanthin. The diversity of carotenoids in peel and juice vesicle tissues and the fact that there was over 250 times higher content of total carotenoids in peels of Yuhuan pummelo than juice vesicles suggested that the biosynthesis of carotenoids in these two tissues was independent and exchange of carotenoids between the tissues was not likely. Lutein was observed in peels of pummelos and grapefruits and juice vesicles of ordinary pummelo but not in orange tissues. Accumulation of lycopene and beta-carotene was observed in red mutant citrus, except for the peel of Cara Cara red orange. Additionally, phytoene accumulated in all tissues except for the peel of Chuzhou Early Red pummelo. No obvious change in the total content of xanthophylls was observed in the Cara Cara red orange. Ordinary grapefruit (Marsh) tissues and pummelo (Yuhuan) juice vesicles were almost devoid of carotenoids, and in red mutants, the content of total carotenoids increased dramatically up to 790-fold. The different changes in carotenoid content and profiles in mutant(s) of different citrus species suggest that the underlying mechanisms for the mutations might be different.     

Scavenging capacity of berry crops on superoxide radicals, hydrogen peroxide, hydroxyl radicals, and singlet oxygen

The antioxidant activities against superoxide radicals (O(2)(*)(-)), hydrogen peroxide (H(2)O(2)), hydroxyl radicals (OH(*)), and singlet oxygen ('O(2)) was evaluated in fruit juice from different cultivars of thornless blackberries (Rubus sp.), blueberries (Vaccinium spp.), cranberries (Vaccinium macrocarpon Aiton), raspberries (Rubus idaeus L. and Rubus occidentalis L.), and strawberries (Fragaria x ananassa Duch.). Among the different cultivars, juice of 'Hull Thornless' blackberry, 'Earliglow' strawberry, 'Early Black' cranberry, 'Jewel' raspberry, and 'Elliot' blueberry had the highest antioxidant capacity against superoxide radicals (O(2)(*)(-)), hydrogen peroxide (H(2)O(2)), hydroxyl radicals (OH(*)), and singlet oxygen ('O(2)). In general, blackberries had the highest antioxidant capacity inhibition of O(2)(*)(-), H(2)O(2), and OH(*). Strawberry was second best in the antioxidant capacity assay for these same free radicals. With regard to 'O(2) scavenging activity, strawberry had the highest value, while blackberry was second. Cranberries had the lowest inhibition of H(2)O(2) activity. Meanwhile, blueberries had the lowest antioxidant capacity against OH(*) and 'O(2). There were interesting and marked differences among the different antioxidants in their abilities to scavenge different reactive oxygen species. beta-Carotene had by far the highest scavenging activity against 'O(2) but had absolutely no effect on H(2)O(2). Ascorbic acid was the best at inhibiting H(2)O(2) free radical activity. For OH(*), there was a wide range of scavenging capacities from a high of 15.3% with alpha-tocopherol to a low of 0.88% with ascorbic acid. Glutathione had higher O(2)(*)(-) scavenging capacity compared to the other antioxidants.     

Comparison of antioxidant potency of commonly consumed polyphenol-rich beverages in the United States

A number of different beverage products claim to have antioxidant potency due to their perceived high content of polyphenols. Basic and applied research indicates that pomegranate juice (PJ), produced from the Wonderful variety of Punica granatum fruits, has strong antioxidant activity and related health benefits. Although consumers are familiar with the concept of free radicals and antioxidants, they are often misled by claims of superior antioxidant activity of different beverages, which are usually based only on testing of a limited spectrum of antioxidant activities. There is no available direct comparison of PJ's antioxidant activity to those of other widely available polyphenol-rich beverage products using a comprehensive variety of antioxidant tests. The present study applied (1) four tests of antioxidant potency [Trolox equivalent antioxidant capacity (TEAC), total oxygen radical absorbance capacity (ORAC), free radical scavenging capacity by 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP)]; (2) a test of antioxidant functionality, that is, inhibition of low-density lipoprotein (LDL) oxidation by peroxides and malondialdehyde methods; and (3) evaluation of the total polyphenol content [by gallic acid equivalents (GAEs)] of polyphenol-rich beverages in the marketplace. The beverages included several different brands as follows: apple juice (3), a?aí juice (3), black cherry juice (3), blueberry juice (3), cranberry juice (3), Concord grape juice (3), orange juice (3), red wines (3), iced tea beverages (10) [black tea (3), green tea (4), white tea (3)], and a major PJ available in the U.S. market. An overall antioxidant potency composite index was calculated by assigning each test equal weight. PJ had the greatest antioxidant potency composite index among the beverages tested and was at least 20% greater than any of the other beverages tested. Antioxidant potency, ability to inhibit LDL oxidation, and total polyphenol content were consistent in classifying the antioxidant capacity of the polyphenol-rich beverages in the following order: PJ>red wine>Concord grape juice>blueberry juice>black cherry juice, a?aí juice, cranberry juice>orange juice, iced tea beverages, apple juice. Although in vitro antioxidant potency does not prove in vivo biological activity, there is also consistent clinical evidence of antioxidant potency for the most potent beverages including both PJ and red wine.     

Antioxidant activity of apple peels

Consumption of fruits and vegetables has been shown to be effective in the prevention of chronic diseases. These benefits are often attributed to the high antioxidant content of some plant foods. Apples are commonly eaten and are large contributors of phenolic compounds in European and North American diets. The peels of apples, in particular, are high in phenolics. During applesauce and canned apple manufacture, the antioxidant-rich peels of apples are discarded. To determine if a useful source of antioxidants is being wasted, the phytochemical content, antioxidant activity, and antiproliferative activity of the peels of four varieties of apples (Rome Beauty, Idared, Cortland, and Golden Delicious) commonly used in applesauce production in New York state were investigated. The values of the peels were compared to those of the flesh and flesh + peel components of the apples. Within each variety, the total phenolic and flavonoid contents were highest in the peels, followed by the flesh + peel and the flesh. Idared and Rome Beauty apple peels had the highest total phenolic contents (588.9 +/- 83.2 and 500.2 +/- 13.7 mg of gallic acid equivalents/100 g of peels, respectively). Rome Beauty and Idared peels were also highest in flavonoids (306.1 +/- 6.7 and 303.2 +/- 41.5 mg of catechin equivalents/100 g of peels, respectively). Of the four varieties, Idared apple peels had the most anthocyanins, with 26.8 +/- 6.5 mg of cyanidin 3-glucoside equivalents/100 g of peels. The peels all had significantly higher total antioxidant activities than the flesh + peel and flesh of the apple varieties examined. Idared peels had the greatest antioxidant activity (312.2 +/- 9.8 micromol of vitamin C equivalents/g of peels). Apple peels were also shown to more effectively inhibit the growth of HepG(2) human liver cancer cells than the other apple components. Rome Beauty apple peels showed the most bioactivity, inhibiting cell proliferation by 50% at the low concentration of 12.4 +/- 0.4 mg of peels/mL. The high content of phenolic compounds, antioxidant activity, and antiproliferative activity of apple peels indicate that they may impart health benefits when consumed and should be regarded as a valuable source of antioxidants.     

Continuous hot pressurized solvent extraction of 1,1-diphenyl-2-picrylhydrazyl free radical scavenging compounds from Taiwan yams (Dioscorea alata)

This study investigates a semicontinuous hot pressurized fluid extraction process and the scavenging activity on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical of the extract from Taiwan yams (Dioscorea alata). Liquid-liquid extractions were preliminarily employed to generate six fractions, initially extracted by ethanol. Then, the aqueous solution of dried crude ethanol extract was sequentially fractionated by hexane, chloroform, ethyl acetate, and n-butanol. The EC50 value was defined as the UV absorption of DPPH concentrations sufficiently decreased to 50% of the original value. It was found that all peel portions have a better effect on scavenging of the DPPH free radical than meat portions, especially for the ethyl acetate partition of the peel portion of Tainung #2 yam. Its EC50 value (14.5 microg mL(-1)) was even lower than that of ascorbic acid (21.4 microg mL(-1)). Furthermore, semicontinuous hot pressurized ethanol was superior to hot pressurized water in extracting the compound scavenging the DPPH radical from the Purpurea-Roxb peel. The recovery of four unknown compounds corresponded to the scavenging ratio of DPPH free radical in the hot pressurized ethanol extract. Finally, three-level and four-factor experimental design revealed that ethanol ratio and temperature were the most effective factors in order. Conditions of 80% of aqueous ethanol, 20.0 kg/kg solid ratio, 180 psig (1.342 MPa), and 100 degrees C were preferred to extract those antioxidants from the yam peel.     

Lipid peroxidation and coupled vitamin oxidation in simulated and human gastric fluid inhibited by dietary polyphenols: health implications

The Western diet contains large quantities of oxidized lipids, because a large proportion of the food in the diet is consumed in a fried, heated, processed, or stored form. We investigated the reaction that could occur in the acidic pH of the stomach and accelerate the generation of lipid hydroperoxides and cooxidation of dietary vitamins. To estimate the oxygen content in the stomach after food consumption, oxygen released from masticated bread (20 g) into deoxygenated water (100 mL) was measured. Under these conditions, the oxygen concentration rose by 250 microM and reached a full oxygen saturation. The present study demonstrated that heated red meat homogenized in human gastric fluid, at pH 3.0, generated hydroperoxides and malondialdehyde. The cross-reaction between free radicals produced during this reaction cooxidized vitamin E, beta-carotene, and vitamin C. Both lipid peroxidation and cooxidation of vitamin E and beta-carotene were inhibited at pH 3.0 by red wine polyphenols. Ascorbic acid (44 mg) at a concentration that represented the amount that could be ingested during a meal inhibited lipid peroxidation only slightly. Red wine polyphenols failed to prevent ascorbic acid oxidation significantly but, in conjunction with ascorbic acid, did inhibit lipid peroxidation. In the presence of catechin, a well-known polyphenol found in red wine, ascorbic acid at pH 3.0 works in a synergistic manner preventing lipid peroxidation and beta-carotene cooxidation. The present data may explain the major benefits to our health and the crucial role of consuming food products rich in dietary antioxidants such as fruits, vegetables, red wines, or green tea during the meal.     

Phenol antioxidant quantity and quality in foods: fruits.

The free and bound phenols have been measured in 20 fruits commonly consumed in the American diet. Phenols were measured colorimetrically using the Folin-Ciocalteu reagent with catechin as the standard after correction for ascorbic acid contribution. On a fresh weight basis, cranberry had the highest total phenols, and was distantly followed by red grape. Free and total phenol quality in the fruits was analyzed by using the inhibition of lower density lipoprotein oxidation promoted by cupric ion. Ascorbate had only a minor contribution to the antioxidants in fruits with the exception of melon, nectarine, orange, white grape, and strawberry. The fruit extracts' antioxidant quality was better than the vitamin antioxidants and most pure phenols, suggesting synergism among the antioxidants in the mixture. Using our assay, fruits had significantly better quantity and quality of phenol antioxidants than vegetables. Fruits, specifically apples and cranberries, have phenol antioxidants that can enrich lower density lipoproteins and protect them from oxidation. The average per capita consumption of fruit phenols in the U.S. is estimated to be 255 mg/day of catechin equivalents.     

Simple assessment of radical scavenging capacity of beverages

The radical-scavenging antioxidants play an important role against oxidative stress in the defense system in vivo. The beneficial effects of antioxidants contained in foods and beverages have been well-accepted, and their antioxidant capacity has been assessed by various methods. In the present study, a simple method is proposed in which the total radical scavenging capacity is assessed from the bleaching of pyranine and pyrogallol red induced by free radicals generated from azo initiator. The total content of antioxidants contained in red wine, green tea, and cassis drink and their reactivities toward peroxyl radicals were measured from the lag phase and rate of bleaching using pyranine and pyrogallol red as a probe, respectively. It was found that this method to follow the bleaching of two probes by visible light spectrophotometer is convenient and applicable for assessment of total radical scavenging capacity of both content and activity of the antioxidants contained in beverages.     

Free radical scavenging properties of conjugated linoleic acids.

Conjugated linoleic acids (CLA) were investigated for free radical scavenging properties against the stable 2,2-diphenyl-1-picryhydrazyl radical (DPPH.) by electron spin resonance (ESR) spectrometry and spectrophotometric methods. ESR results demonstrated that CLA directly reacted and quenched free DPPH radicals in benzene, while spectrophotometric analysis showed the radical scavenging capacity of CLA in ethanol. Dose and time effects of CLA-DPPH. reactions were observed in both tests. The ED(50) of CLA was 18 mg/mL under experimental conditions. CLA are much weaker radical scavengers as compared to vitamin E, vitamin C, and BHT. Kinetics of CLA-DPPH. reactions was different to that of linoleic acid (LA)-DPPH. reactions. CLA reacted and quenched DPPH radicals at all tested levels without a lag phase, while LA had a lag phase and showed no radical quenching activity at levels of 5-80 mg/mL in 30 min. These data indicated that CLA can provide immediate protection against free radicals, but LA cannot.     

Antioxidant properties of various solvent extracts of total phenolic constituents from three different agroclimatic origins of drumstick tree (Moringa oleifera Lam.) leaves

Water, aqueous methanol, and aqueous ethanol extracts of freeze-dried leaves of Moringa oleifera Lam. from different agroclimatic regions were examined for radical scavenging capacities and antioxidant activities. All leaf extracts were capable of scavenging peroxyl and superoxyl radicals. Similar scavenging activities for different solvent extracts of each collection were found for the stable 1,1-diphenyl 2-picrylhydrazyl (DPPH(*)) radical. Among the three different moringa samples, both methanol and ethanol extracts of Indian origins showed the highest antioxidant activities, 65.1 and 66.8%, respectively, in the beta-carotene-linoleic acid system. Nonetheless, increasing concentration of all the extracts had significantly (P < 0.05) increased reducing power, which may in part be responsible for their antioxidant activity. The major bioactive compounds of phenolics were found to be flavonoid groups such as quercetin and kaempferol. On the basis of the results obtained, moringa leaves are found to be a potential source of natural antioxidants due to their marked antioxidant activity. This is the first report on the antioxidant properties of the extracts from freeze-dried moringa leaves. Overall, both methanol (80%) and ethanol (70%) were found to be the best solvents for the extraction of antioxidant compounds from moringa leaves.     

Rapid peroxyl radical scavenging capacity (PSC) assay for assessing both hydrophilic and lipophilic antioxidants

This paper reports a simple, rapid, and sensitive assay for assessing peroxyl radical scavenging capacity (PSC) of both hydrophilic and lipophilic antioxidant compounds and food extracts. The assay is based on the degree of inhibition of dichlorofluorescin oxidation by antioxidants that scavenge peroxyl radicals, generated from thermal degradation of 2,2'-azobis(amidinopropane). For hydrophilic antioxidant activity, the dose required to cause a 50% inhibition of the reaction (EC(50)) ranged from 2.41 +/- 0.02 (EGCG) to 21.26 +/- 0.38 microM (ferulic acid). EC(50) values for the hydrophilic antioxidant activity of food extracts ranged from 309.2 +/- 3.63 (apple) to 3345.1 +/- 151.5 micromol of vitamin C equiv/100 g for wheat bran. The EC(50) values for lipophilic antioxidant activity were 1.58 +/- 0.11 (Trolox), 4.35 +/- 0.43 (alpha-tocopherol), 18.94 +/- 0.38 (BHA), and 182.69 +/- 13.7 microM (BHT). Whole grain lipophilic antioxidant activity ranged from 3.49 +/- 0.57 (wheat) to 8.79 +/- 1.98 micromol of alpha-tocopherol equiv/100 g of rice. Hydrophilic antioxidant activity contributed >98% of the total antioxidant activity (hydrophilic plus lipophilic) of whole grains tested. The PSC assay was accurate (86-108% recovery), precise (0.12-11% CV), and reproducible (12% RSD) and produced results comparable to those of similar published assays. The PSC assay can be routinely used to analyze or screen both hydrophilic and lipophilic antioxidants or food extracts and will be a valuable alternative biomarker for future epidemiological studies of chronic diseases.     

Carotenoids in white- and red-fleshed loquat fruits

Fruits of 23 loquat ( Eriobotrya japonica Lindl.) cultivars, of which 11 were white-fleshed and 12 red-fleshed, were analyzed for color, carotenoid content, and vitamin A values. Color differences between two loquat groups were observed in the peel as well as in the flesh. beta-Carotene and lutein were the major carotenoids in the peel, which accounted for about 60% of the total colored carotenoids in both red- and white-fleshed cultivars. beta-Cryptoxanthin and, in some red-fleshed cultivars, beta-carotene were the most abundant carotenoids in the flesh, and in total, they accounted for over half of the colored carotenoids. Neoxanthin, violaxanthin, luteoxanthin, 9- cis-violaxanthin, phytoene, phytofluene, and zeta-carotene were also identified, while zeaxanthin, alpha-carotene, and lycopene were undetectable. Xanthophylls were highly esterified. On average, 1.3- and 10.8-fold higher levels of colored carotenoids were observed in the peel and flesh tissue of red-fleshed cultivars, respectively. The percentage of beta-carotene among colored carotenoids was higher in both the peel and the flesh of red-fleshed cultivars. Correlations between the levels of total colored carotenoids and the color indices were analyzed. The a* and the ratio of a*/ b* were positively correlated with the total content of colored carotenoids, while L*, b*, and H degrees correlated negatively. Vitamin A values, as retinol equivalents (RE), of loquat flesh were 0.49 and 8.77 microg/g DW (8.46 and 136.41 microg/100 g FW) on average for white- and red-fleshed cultivars, respectively. The RE values for the red-fleshed fruits were higher than fruits such as mango, red watermelon, papaya, and orange as reported in the literature, suggesting that loquat is an excellent source of provitamin A.     

Effect of regulated deficit irrigation and crop load on the antioxidant compounds of peaches

The use of regulated deficit irrigation (RDI) strategies is becoming a common practice in areas with low water availability. Little information is available about the effects of RDI on the antioxidant content of fruits. In this study, the influence of RDI on the content of vitamin C, phenolic compounds and carotenoids was investigated. Two irrigation strategies, fully irrigated (FI) and RDI, were compared at two levels of thinning, commercial and half of the commercial crop load. RDI strategies affected the content of vitamin C, phenolics and carotenoids of Flordastar peaches. RDI caused fruit peel stress lowering the content of vitamin C and carotenoids, while increasing the phenolic content, mainly anthocyanins and procyanidins. Fruit weight was the only quality index influenced by the crop load as it increased in FI fruits at low crop load. In general, fruits from commercial crop load had slightly higher content of antioxidants to fruits from low crop load, although these influences were only observed in the peel. Additionally, the influence of irrigation controlled by two sensors related to plant water level, maximum daily trunk shrinkage (MDS) and sap flow (SF) on the antioxidant constituents of peaches was evaluated. The response of the fruits to SF sensor was similar to that observed for RDI strategy. According to the tested water sensors, SF did not act as a good plant-based water indicator for use in irrigation scheduling, as it caused an increase in the content of phenolics, similar to that observed for fruits subjected to RDI. Therefore, selection of RDI strategies and plant water indicators should be taken into account as they affect the content of antioxidants of peaches.     

In situ and in vitro antioxidant activity of sweetpotato anthocyanins

Anthocyanins from a variety of fruits and vegetables have been shown to possess potent antioxidant activity in vitro, but scavenging of free radicals by anthocyanins has only been demonstrated in situ in the leaves of certain plants. We report on a new sweetpotato that exhibits mottled purple flesh attributable to high concentrations of anthocyanins. By perfusing transverse sweetpotato sections with the reactive oxygen species H(2)O(2), followed by the H(2)O(2) sensitive fluorochrome scopletin, we show that anthocyanins act as antioxidants in situ within the sweetpotato storage roots. We also demonstrate in vitro antioxidant activity by sweetpotato anthocyanins, where an additive effect with hydroxycinnamic acids is observed. Anthocyanic foods have been shown to offer protection against a variety of degenerative disease processes. Given that sweetpotato can be eaten several hundred grams at a time and as a staple, these data are consistent with the possibility of superior health protection by anthocyanic varieties of sweetpotato in comparison to most common fruits and vegetables.     

In vitro activity of almond skin polyphenols for scavenging free radicals and inducing quinone reductase

Observational studies and clinical trials suggest nut intake, including almonds, is associated with an enhancement in antioxidant defense and a reduction in the risk of cancer and cardiovascular disease. Almond skins are rich in polyphenols (ASP) that may contribute to these putative benefits. To assess their potential mechanisms of action, we tested the in vitro effect of ASP extracted with methanol (M) or a gastrointestinal juice mimic (GI) alone or in combination with vitamins C (VC) or E (VE) (1-10 micromol/L) on scavenging free radicals and inducing quinone reductase (QR). Flavonoid profiles from ASP-M and -GI extracts were different from one another. ASP-GI was more potent in scavenging HOCl and ONOO (-) radicals than ASP-M. In contrast, ASP-M increased and ASP-GI decreased QR activity in Hepa1c1c7 cells. Adding VC or VE to ASP produced a combination- and dose-dependent action on radical scavenging and QR induction. In comparison to their independent actions, ASP-M plus VC were less potent in scavenging DPPH, HOCl, ONOO (-), and O 2 (-) (*). However, the interaction between ASP-GI plus VC promoted their radical scavenging activity. Combining ASP-M plus VC resulted in a synergistic interaction, inducing QR activity, but ASP-GI plus VC had an antagonistic effect. On the basis of their total phenolic content, the measures of total antioxidant activity of ASP-M and -GI were comparable. Thus, in vitro, ASP act as antioxidants and induce QR activity, but these actions are dependent upon their dose, method of extraction, and interaction with antioxidant vitamins.     

Synergistic effects of thiols and amines on antiradical efficiency of protocatechuic acid

DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity of protocatechuic acid and its structural analogues (methyl protocatechuate, 3',4'-dihydroxyacetophenone, 3,4-dihydroxybenzaldehyde, and 3,4-dihydroxybenzonitrile) were examined in aprotic and protic solvents. In aprotic acetonitrile, all test compounds scavenged two radicals. In protic methanol, however, these compounds rapidly scavenged five radicals except for protocatechuic acid, which consumed only two radicals. The result indicated that higher radical scavenging activity in methanol than in acetonitrile was due to a nucleophilic addition of the methanol molecule on the oxidized quinones, which led to a regeneration of catechol structures. To investigate the importance of the nucleophilic addition on the quinones for the high radical scavenging activity, DPPH radical scavenging activity of protocatechuic acid and its analogues was examined in the presence of a variety of nucleophiles. The addition of a strong nucleophile such as a cysteine derivative significantly increased the radical scavenging equivalence. Furthermore, thiol adducts at C-2 and C-2,5 of protocatechuic acid and its analogues were isolated from the reaction mixtures. These results strongly suggest that the quinone of protocatechuic acid and its analogues undergo a nucleophilic attack at C-2 to yield 2-substituted-3,4-diols. Then, a regenerated catechol moiety of adducts scavenge two additional radicals by reoxidation into quinones, which undergo the second nucleophilic attack at the C-5. This mechanism demonstrates a possibility of synergistic effects of various nucleophiles on the radical scavenging ability of plant polyphenols containing a 3,4-dihydroxy substructure like protocatechuic acid and its analogues.     

Effect of reddening-ripening on the antioxidant activity of polyphenol extracts from cv. 'Annurca' apple fruits

Apple is among the most consumed fruits worldwide, and several studies suggest that apple polyphenols could play a role in the prevention of degenerative diseases. 'Annurca' apple fruit undergoes, after harvest, a typical reddening treatment to turn the apples' skin red, and it is noted for its high firmness. This paper reports the effect of reddening-ripening treatment on polyphenol concentration and antioxidant activity of both peel and flesh extracts. The in vitro antioxidant properties have been compared with the protective effect against the cytotoxic effects of reactive oxygen species using Caco-2 cells as model system. Pretreatment of cells with different polyphenolic apple extracts provides a remarkable protection against oxidative damage. This effect seems to be associated with the antioxidant activity of 'Annurca' apple polyphenolic compounds. The flesh has antioxidant properties comparable to those possessed by the peel. Neither the reddening nor the fruit conservation causes changes in the antioxidant properties possessed by this apple variety. The data indicate that polyphenolic compounds in 'Annurca' apples are relatively stable in the peel and also in the flesh; therefore, the health benefits of polyphenols should be maintained during long-term storage. Finally, a diet rich in apple antioxidants could exert a beneficial effect in the prevention of intestinal pathologies related to the production of reactive oxygen species.     

Antioxidative efficacy of alkali-treated tilapia protein hydrolysates: a comparative study of five enzymes

The antioxidant activities of alkali-treated tilapia protein hydrolysates were determined by their ability to inhibit the formation of lipid hydroperoxides (PV) and thiobarbituric acid reactive substances (TBARS) in a washed muscle model system and by their ability to inhibit DPPH free radicals and chelate ferrous ion in an aqueous solution. Protein isolates were prepared from tilapia white muscle using alkali solubilization at pH 11.0 and reprecipitation at pH 5.5. Protein hydrolysates were prepared by hydrolyzing the isolates using five different enzymes, Cryotin F, Protease A Amano, Protease N Amano, Flavourzyme, and Neutrase, to 7.5, 15, and 25% degrees of hydrolysis (DH). All of the protein hydrolysates significantly (p<0.05) inhibited the development of TBARS and PV. The antioxidant activity of the hydrolysates increased with the DH. Also, the antioxidant activity of the hydrolysates varied significantly (p<0.05) among the different enzymes. The ability of different enzyme-catalyzed protein hydrolysates to scavenge DPPH radicals was not reflected in their ability to inhibit oxidation in a washed tilapia model system. In a washed muscle model system, the hydrolysates prepared using Cryotin F were most effective and the hydrolysates prepared using Flavourzyme and Neutrase were least effective in inhibiting the development of TBARS and PV, whereas in an aqueous solution, hydrolysates prepared using Flavourzyme were most effective in scavenging DPPH radicals and chelating ferrous ions. Enzymatic hydrolysis decreased the size of tilapia protein hydrolysates and, in general, tilapia protein hydrolysates with low molecular weights were better antioxidants than those with high molecular weights.