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1.
Bee-collected pollen ("bee pollen") is promoted as a health food with a wide range of nutritional and therapeutic properties. The objective of the current study is to evaluate the contribution made through the free radical scavenging capability of bee-collected floval pollens by their flavonoid/phenolics constituents, and to determine whether this capability is affected by aging. The free radical scavenging effectiveness of a bee pollen (EC(50)) as measured by the DPPH method is shown to be determined by the nature and levels of the constituent floral pollens, which can be assayed via their phenolics profiles by HPLC. Each pure floral pollen has been found to possess a consistent EC(50) value, irrespective of its geographic origin or date of collection, and the EC(50) value is determined to a large extent (ca. 50%) by the nature and the levels of the pollen's flavonoids and phenolic acids. Non-phenolic antioxidants, possibly proteins, account for the balance of the activity. Pollen aging over 3 years is demonstrated to reduce the free radical scavenging activity by up to 50% in the most active floral pollens, which tend to contain the highest levels of flavonoids/phenolic acids. It is suggested that the freshness of a bee pollen may be determined from its free radical scavenging capacity relative to that of fresh bee pollen containing the same floral pollen mix.  相似文献   

2.
DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging reactions of protocatechuic and gallic acids, and their methyl esters, have been investigated by NMR. In acetone, methyl protocatechuate was gradually converted to a Diels-Alder adduct of two molecules of the intermediate quinone in the reaction with DPPH radical, whereas methyl gallate rapidly gave a symmetrical dimer via a putative quinone precursor. Both dimers are rather unstable and their structures have been deduced by in situ NMR measurements of the reaction mixtures. Gallic acid also gave a corresponding symmetrical dimer in the same reaction as methyl gallate, although protocatechuquinone produced from protocatechuic acid did not yield a Diels-Alder adduct, unlike its methyl ester. Interestingly, these dimer formations were not observed in methanol solution.  相似文献   

3.
The amino acid composition of 53 honey samples from Spain, consisting of 39 floral, 5 honeydew, and 9 blend honeys, has been determined. Physicochemical characteristics, polyphenolic content, amino acid composition, and estimation of the radical scavenging capacity against the stable free radical DPPH of the honey samples were analyzed. The resulting data have been statistically evaluated. The results showed that pH, acidity, net absorbance, electrical conductivity, and total polyphenolic contents of the honeys showed a strong correlation with the radical scavenging capacity. The correlation between the radical scavenging capacity of honey and amino acid contents was high with 18 of the 20 amino acids detected, with correlation values higher than those obtained for polyphenolic content. These results suggest that the amino acid composition of honey is an indicator of the sample's scavenging capacity.  相似文献   

4.
Foods rich with unsaturated fatty acids are prone to enzymatic and nonenzymatic lipid peroxidation; lipoxygenase, a metalloenzyme and a free radical former, oxidizes polyunsaturated fatty acids and is one of the key enzymes in lipid oxidation. Here, we report sclerotiorin, purified from the fermented broth of Penicillium frequentans, as a potent reversible, uncompetitive inhibitor against soybean lipoxygenase-1 (LOX-1) with a half-maximal value (IC50) of 4.2 microM. The inhibitor also showed an antioxidant property by scavenging free radical with an ED50 of 0.12 microM; in addition, nonenzymatic lipid peroxidation was inhibited with a PD50 value of 64 microM and did not show metal chelation. The observations made in this study suggest that sclerotiorin possibly inhibits LOX in two ways: one, by interacting with the enzyme-substrate complex, and two, as an antioxidant by quenching or trapping the free radical intermediates formed in the enzyme reaction. Sclerotiorin compares well with other known natural and synthetic lipoxygenase inhibitors.  相似文献   

5.
Proteins dispersed in the continuous phase of oil-in-water emulsions are capable of inhibiting lipid oxidation reactions. The antioxidant activity of these proteins is thought to encompass both free radical scavenging by amino acid residues and chelation of prooxidative transition metals; however, the precise mechanism by which this occurs remains unclear. In this study, the oxidative stability of cysteine, tryptophan, and methionine residues in continuous phase beta-lactoglobulin (beta-Lg) in a Brij-stabilized menhaden oil-in-water emulsion was determined. The presence of low concentrations of continuous phase beta-Lg (250 and 750 microg/mL) significantly inhibited lipid oxidation as determined by lipid hydroperoxides and thiobarbituric acid reactive substances analysis. It was observed that cysteine oxidized before tryptophan in beta-Lg, and both residues oxidized before lipid oxidation could be detected. No oxidation of the methionine residues of beta-Lg was observed despite its reported high oxidative susceptibility. It is conceivable that surface exposure of amino acid residues greatly affects their oxidation kinetics, which may explain why some residues are preferentially oxidized relative to others. Further elucidation of the mechanisms governing free radical scavenging of amino acids could lead to more effective applications of proteins as antioxidants within oil-in-water food emulsions.  相似文献   

6.
Centaurium erythraea Rafin. (Gentianaceae) has long been used in traditional medicine. This plant contains considerable amounts of polyphenolic compounds, namely, xanthones and phenolic acids as the main constituents. Because phenolic groups exhibit activity as radical scavengers and/or metal chelators, this study evaluated the superoxide radical scavenging properties of a lyophilized infusion obtained from C. erythraea flowering tops. Superoxide radical scavenging activity was assayed using enzymatic (xanthine/xanthine oxidase) and nonenzymatic (NADH/phenazine methosulfate) superoxide generating systems. This study provided evidence that C. erythraea exhibits interesting antioxidant properties, expressed either by the capacity to scavenge superoxide radical or to noncompetitively inhibit xanthine oxidase. The main phenolic compounds present in this extract were several esters of hydroxycinnamic acids, namely, p-coumaric, ferulic, and sinapic acids.  相似文献   

7.
In this work, the angiotensin-converting enzyme (ACE)-inhibitory and radical-scavenging activities of the beta-lactoglobulin (beta-Lg)-derived peptides WY f(19-20), WYS f(19-21), WYSL f(19-22), WYSLA f(19-23), WYSLAM f(19-24), and WYSLAMA f(19-25) have been determined. The ACE-inhibitory activity (IC50) varied from 38.3 to 90.4 microM, with the exception of WYS (>500 microM). All beta-Lg-derived peptides also exhibited radical-scavenging activity (oxygen radical absorbance capacity (ORAC) values ranged from 4.45 to 7.67 micromol Trolox equivalents/micromol of peptide). The presence and position of amino acids Trp, Tyr, and Met were proposed to be responsible for the antioxidant activity. The equimolar amino acid mixtures of all the peptides showed ORAC values lower than those of the corresponding peptides, indicating that the peptidic bond or the structural conformation had a positive influence on this activity. Finally, positive antioxidant effects of WYS, WYSL, and WYLA with ascorbic acid were observed, whereas WY and WYSLAM showed negative effects, both cases for different molar ratio mixtures. These results should be taken into account in the development of new food ingredients on the basis of peptides from beta-Lg.  相似文献   

8.
葛晓鸣  顾伟  徐永健 《核农学报》2019,33(2):322-329
为了探讨大海马蛋白质的高效利用方法,本试验将脱脂大海马粉经碱性蛋白酶和胰蛋白酶联合消解后,酶解液(PH)经超滤膜分离为5组分(PH-Ⅰ、PH-Ⅱ、PH-Ⅲ、PH-Ⅳ、PH-Ⅴ),结合各组分的氨基酸组成,回归分析了各组分的自由基清除能力与氨基酸组成间的相关关系。结果表明,酶解液经超滤膜分离的5组分中PH-Ⅴ(<2 500 Da)抗氧化能力较强,清除DPPH自由基能力为34.2%±0.1%,对超氧阴离子的清除能力为29.2%±0.1%,Fe3+还原力为0.28%±0.1%。海马酶解多肽各组成中疏水性氨基酸含量低于亲水性氨基酸,但疏水性氨基酸对自由基的清除能力起着决定性作用,极性氨基酸和非极性氨基酸可通过协同作用来增强海马多肽清除自由基的能力,且每个单位极性氨基酸的抗氧能力是非极性氨基酸的1.2倍,每个单位芳香族氨基酸的抗氧化能力是脂肪族氨基酸的2倍。本研究不仅制备了一类具有开发价值的抗氧化多肽,并且分析了多肽抗氧化能力与氨基酸组成的相关关系,为大海马的高值化利用提供了理论依据。  相似文献   

9.
Swiss red wheat grain, bran, aleurone, and micronized aleurone were examined and compared for their free radical scavenging properties against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH*), radical cation ABTS*+ and peroxide radical anion O(2)*-, oxygen radical absorbance capacity (ORAC), chelating capacity, total phenolic content (TPC), and phenolic acid composition. The results showed that micronized aleurone, aleurone, bran, and grain may significantly differ in their antioxidant properties, TPC, and phenolic acid composition. Micronized aleurone had the greatest antioxidant activities, TPC, and concentrations of all identified phenolic acids, suggesting the potential of postharvesting treatment on antioxidant activities and availability of TPC and phenolic acids. Ferulic acid was the predominant phenolic acid in Swiss red wheat and accounted for approximately 57-77% of total phenolic acids on a weight basis. Ferulic acid concentration was well correlated with scavenging activities against radical cation and superoxide anion, TPC, and other phenolic acid concentrations, suggesting the potential use of ferulic acid as a marker of wheat antioxidants. In addition, 50% acetone and ethanol were compared for their effects on wheat ORAC values. The ORAC value of 50% acetone extracts was 3-20-fold greater than that of the ethanol extracts, indicating that 50% acetone may be a better solvent system for monitoring antioxidant properties of wheat. These data suggest the possibility to improve the antioxidant release from wheat-based food ingredients through postharvesting treatment or processing.  相似文献   

10.
The antioxidant activity of 12 aqueous commercial smoke flavorings used in the food industry was determined by two methods: bleaching of the carotenoid crocin and scavenging of the DPPH radical. The reaction with the DPPH radical was evaluated by calculating the effective concentration (EC50) and the antiradical efficiency (AE). A gas chromatography-mass spectrometry method was, moreover, used for the determination of 2-methoxyphenols, 2,6-dimethoxyphenols, and dihydroxybenzenes. The methoxyphenols were extracted from the aqueous smoke by dichloromethane, and also the residue aqueous phase was analyzed to determine the more water-soluble dihydroxybenzenes. The recovery and the repeatability of the method are reported. The total phenolic concentrations of the smoke flavorings showed a wide range, from about 1000 to 25000 mg/kg. Considering the three classes of compounds, the concentrations were about 300-3000 mg/kg for the 2-methoxyphenols, 200-11000 mg/kg for the 2,6-dimethoxyphenols, and 140-10000 mg/kg for the dihydroxybenzenes. The range of the antioxidant activities of the smoke flavorings was wide, reflecting the wide range of the phenolic concentrations. Good correlations were obtained between the total phenolic concentration and the antioxidant activities determined by both the DPPH and crocin assays.  相似文献   

11.
Plant-derived polyphenolic compounds have received much attention for their ability to sequester high-energy free radicals in a great variety of food-related and biological systems, protecting those systems from oxidative change. The ability of these compounds to scavenge free radicals has always been attributed to their phenolic functionality, from which a hydrogen atom can be easily abstracted. In this study, the cinnamates and the ubiquitous hydroxycinnamates were found to equally suppress the formation of oxidation products in wine exposed to the Fenton reaction (catalytic Fe(II) with hydrogen peroxide). Mechanistic investigations led to the unexpected discovery that the α,β-unsaturated side chain of cinnamic acids could efficiently trap 1-hydroxyethyl radicals, representing a newly discovered mode of antioxidant radical scavenging activity for these broadly occurring compounds in a food system. The proposed pathway is supported by prior fundamental studies with radiolytically generated radicals.  相似文献   

12.
Tannin-protein complexes as radical scavengers and radical sinks   总被引：8，自引：0，他引：8  
The 2,2'-azinobis(3-ethylbenzothiazoline 6-sulfonic acid) radical cation (ABTS(*)(+)) decolorization assay has been used to determine the antioxidant activity of the polyphenol epicatechin(16) (4 --> 8) catechin (procyanidin, PC) alone or in complex with the model proteins bovine serum albumin (BSA) or gelatin. PC had a molar antioxidant capacity of approximately 54, 92, or 108 radicals at pH values of 3.0, 4.9, or 7.4, respectively. Radical scavenging occurred via a rapid step followed by a slow step. Interaction with gelatin reduced the rate of rapid scavenging by 50% (PC-BSA mixtures reduced by 15%). Inhibition paralleled formation of precipitable PC-protein complexes over a range of protein/PC ratios. However, inhibition was virtually overcome in 10 min. Reaction with ABTS(*)(+) converted the PC-protein complexes from a dissociable form to a form resistant to dissociation by strong denaturants such as SDS. This study demonstrates that PC is a potent ABTS(*)(+) scavenger even when bound to protein and that the complexes may act as a radical sink within the gastrointestinal tract.  相似文献   

13.
The antioxidant activity of fresh and rehydrated sea cucumber (Cucumaria frondosa) samples with/without internal organs was evaluated for the first time. In addition, their proximate, amino acid, and fatty acid compositions were examined. Rehydrated sea cucumber samples in distilled water were prepared from oven-dried products. All samples contained 83-90% moisture, but showed a significant difference among groups in their protein and lipid contents. Glutamic acid was the predominant amino acid in sea cucumber, followed by glycine and aspartic acid. Essential amino acids such as leucine and lysine were also present at high levels. The trend for free amino acid was different from that of total amino acids and varied among groups. Lipids in sea cucumber were dominated by eicosapentaenoic acid (EPA, C20:5n-3), ranging from 43.2 to 56.7% of the total fatty acids. Docosahexaenoic acid (DHA, C22:6n-3) was present at a much lower concentration of 2.0-5.8%. All sea cucumber samples exhibited radical scavenging property against 2,2'-azobis(2-aminopropane) dihydrochloride (AAPH) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, with rehydrated samples, especially those with internal organs, possessing higher antioxidant activity than their fresh counterparts. No correlation existed between radical scavenging capacity and total phenolics content, suggesting that other components, in addition to phenolic compounds, contribute to the antioxidant activity of sea cucumber.  相似文献   

14.
Dihydroferulic acid (DFA) and dihydrosinapic acid (DSA) were isolated from Kurosu (unpolished rice vinegar) as the major constituents responsible for Kurosu's radical scavenging activity. The levels of antioxidative activity of DFA and DSA in DPPH radical scavenging were higher than those of their respective structurally related compounds, ferulic acid and sinapic acid. The concentrations of DFA and DSA were low in common rice vinegar (polished rice vinegar), suggesting that Kurosu is more advantageous than rice vinegars as an antioxidative food item. As the concentrations of DFA and DSA were low in unpolished rice, too, these acids are thought to be produced in Kurosu through the process of the fermentation from ferulic acid and sinapic acid, respectively.  相似文献   

15.
The antioxidant activity of three major polyamine conjugates, N,N'-dicoumaroyl-putrescine (DCP), N-p-coumaroyl-N'-feruloylputrescine (CFP), and N,N'-diferuloyl-putrescine (DFP) isolated from corn bran, and their related hydroxycinnamic acids, p-coumaric acid and ferulic acid, were evaluated by three antioxidant in vitro assay systems, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and superoxide and hydroxyl radicals generated by enzymatic and nonenzymatic reactions. Additionally, five phenolic compounds were evaluated for melanogenesis inhibitory activity using mushroom tyrosinase and B16 melanoma cells. Most of the phenolic compounds significantly scavenged DPPH, superoxide, and hydroxyl radicals in a dose-dependent manner. Particularly, DFP showed potent DPPH (IC50 = 38.46 microM) and superoxide (IC50 = 291.62 microM) radical scavenging activities, while DCP exhibited the strongest hydroxyl radical scavenging activity (IC50 = 120.55 microM). CFP also exerted moderate DPPH, superoxide, and hydroxyl radical scavenging activities. Meanwhile, DCP (IC50 = 181.73 microM) showed potent tyrosinase inhibitory activity toward l-tyrosine as the substrate, whereas DFP (IC50 = 733.64 microM) significantly inhibited melanin synthesis in B16 melanoma cells. These current results indicate that these three polyamine conjugates from corn bran may be useful potential sources of natural antioxidants and skin-whitening agents.  相似文献   

16.
A simple detection method for a powerful radical scavenging compound in a mixture containing a large variety of compounds, such as the raw extract of edible plants, was developed using 1,1-diphenyl-2-picrylhydrazyl (DPPH) as the radical reagent. The method was established on the basis of the features of the typical chain-breaking antioxidation reaction mechanism, which suggests that the radical scavenging antioxidant should be converted to other stable nonradical compounds during the reaction. This method requires only a simple HPLC instrument, and the disappearance or decrease in the peak intensity, which is induced by the addition of DPPH. This change is monitored by the HPLC to detect the powerful radical scavenger from the complex mixture. The method was applied to the detection and identification of the most powerful antiradical compound in the extracts of three antioxidatively active plant extracts (Psidium guajava, Citrus depressa, and Hypericum chinense). The radical scavenging efficiency of a newly identified compound from H. chinense was also compared with that of Trolox and catechin using the method.  相似文献   

17.
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.  相似文献   

18.
Several new multifunctional molecules derived from natural sources such as amino acids and hydroxycinnamic acids were synthesized. They exhibit various activities such as emulsifying, UV-protecting, and radical scavenging, thereby conforming to the latest requirements for cosmetic ingredients. The synthesis comprises only a few steps: (i) the amino acid, the acid groups of which are protected by esterification, is coupled with ferulic or caffeic acid; (ii) the p-hydroxyl group of the cinnamic derivative reacts with dodecyl bromide in the presence of potassium carbonate (the resulting compounds are highly lipophilic and tested as water/oil (W/O) emulsifiers); (iii) these molecules, by deprotonating the acid groups of the amino acids, with successive salification, are more hydrophilic, with stronger O/W emulsifying properties. The new multifunctional surfactants might prove useful for the treatment of multiple skin conditions, including loss of cellular antioxidants, damage from free radicals, damage from UV, and others.  相似文献   

19.
The antioxidant activities of aqueous phase beta-lactoglobulin (beta-Lg) and its chymotryptic hydrolysates (CTH) were compared in this study. Proteins and peptides have been shown to inhibit lipid oxidation reactions in oil-in-water emulsions; however, a more fundamental understanding of the antioxidant activity of these compounds in dispersed food lipid systems is lacking. CTH was more effective than an equivalent concentration of beta-Lg in retarding lipid oxidation reactions when dispersed in the continuous phase of Brij-stabilized oil-in-water emulsions (pH 7). Furthermore, it was observed that CTH had higher peroxyl radical scavenging and iron-binding values than beta-Lg. Liquid chromatography-mass spectrometry (LC-MS) was used to measure the rate of oxidation of three oxidatively labile amino acid residues (Tyr, Met, and Phe) in certain CTH peptide fragments. Significant oxidation of specific Tyr and Met residues present in two separate 12 amino acid peptide fragments was observed in the days preceding lipid oxidation (39 and 55% of Tyr and Met were oxidized, respectively, by day 4 of the study); however, no significant oxidation of the Phe residue present in a specific 14 amino acid peptide fragment could be observed during the same time period. These data could suggest that Met and Tyr residues are capable of scavenging radical species and have the potential to improve the oxidative stability dispersed food lipids.  相似文献   

20.
Kinetic study of the aroxyl radical-scavenging action of catechins (epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG)) and related compounds (methyl gallate (MG), 4-methylcatechol (MC), and 5-methoxyresorcinol (MR)) has been performed. The second-order rate constant ( k s) for the reaction of these antioxidants with aroxyl radical has been measured in ethanol and aqueous Triton X-100 micellar solution (5.0 wt %). The k s values decreased in the order of EGCG > EGC > MC > ECG > EC > MG > MR in ethanol, indicating that the reactivity of the OH groups in catechins decreased in the order of pyrogallol B-ring > catechol B-ring > gallate G-ring > resorcinol A-ring. The structure-activity relationship in the free radical-scavenging reaction by catechins has been clarified by the detailed analyses of the pH dependence of k s values. From the results, the p K a values have been determined for catechins. The monoanion form at catechol B- and resorcinol A-rings and dianion form at pyrogallol B- and gallate G-rings show the highest activity for free radical scavenging. It was found that the free radical-scavenging activities of catechins are 3.2-13 times larger than that of vitamin C at pH 7.0.  相似文献   

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