The Antioxidant Activity of Regularly Consumed Fruit and Vegetables Reflects their Phenolic and Vitamin C Composition

Recent studies are emphasising the importance and putative modes of action of specific flavonoids as bioactive components of the diet in in vivo and in vitro models. Thus, it is important to have a clear idea of the major phenolic families of which fruit and vegetables are comprised and the levels contained therein. Regularly consumed fruit and vegetables of mixed varieties available on the UK market were analysed for the composition of the major individual phenolic components. The total phenolic content (applying the Folin assay) and the vitamin C levels were also determined. The antioxidant capacities of aqueous/methanolic extracts were comparatively assessed using the TEAC (Trolox Equivalent Antioxidant Capacity), the FRAP (Ferric Reducing Ability of Plasma) and ORAC (Oxygen Radical Absorbance Capacity) assays, which comprise contributions from polyphenols, simple phenols and the ascorbate component. The results were calculated in terms of 100 &#117 g fresh weight (FW) uncooked portion sizes. Fruit and vegetables rich in anthocyanins (e.g. strawberry, raspberry and red plum) demonstrated the highest antioxidant activities, followed by those rich in flavanones (e.g. orange and grapefruit) and flavonols (e.g. onion, leek, spinach and green cabbage), while the hydroxycinnamate-rich fruit (e.g. apple, tomato, pear and peach) consistently elicited the lower antioxidant activities. The TEAC, FRAP and ORAC values for each extract were relatively similar and well-correlated with the total phenolic and vitamin C contents. The antioxidant activities (TEAC) in terms of 100 &#117 g FW uncooked portion size were in the order: strawberry &#100 raspberry=red plum &#100 red cabbage>>>grapefruit= orange>spinach>broccoli>green grape &#59 onion> green cabbage>pea>apple> cauliflower &#59 pear> tomato &#59 peach=leek>banana &#59 lettuce.     

Total phenolics, flavonoids and antioxidant activity of Saptarangi (Salacia chinensis L.) fruit pulp

Salacia chinensis L. has various beneficial properties including antidiabetic and antioxidant activity. The S. chinensis fruit pulp (SCFP) was extracted with four different solvents (Methanol, ethanol, acetone and water) and was screened for total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity (AOA). The AOA was assessed by evaluating the 1, 1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and metal chelating assay. Methanolic SCFP extract exhibited the highest phenolic content (3.20?±?0.12 mg GAE/g FW) whereas, ethanolic extract showed highest flavonoid content (0.31?±?0.68 mg RE/g FW). The methanolic extract possesses highest antioxidant activity towards DPPH (92.44 %), FRAP (1.939 O.D) and metal chelating activity (74.16 %). AOA (DPPH and FRAP) was significantly correlated with TPC. The results indicated that SCFP is a good natural source of antioxidant compounds for use in food and pharmaceutical industry.     

Phytochemical analysis and evaluation of antioxidant and anti-acetylcholinesterase activities of Euphorbia dendroides L. (Euphorbiaceae) latex

The aim of this study was to evaluate the antioxidant and anti-acetylcholinesterase properties and phytochemical constituents of the latex from Euphorbia dendroides L. (Euphorbiaceae) growing wild in Sicily. Phytochemical analysis revealed that into E. dendroides latex the triterpenoids were the most abundant among the identified compounds. Furthermore, a high content of polyphenols mainly as phenolic acids, was found. The antioxidant and free-radical scavenging properties, by several in vitro assays such as DPPH, TEAC and FRAP, have been evaluated. The results showed that E. dendroides latex has significant antioxidant activity, as measured by DPPH assay (2927.01?±?98.03 µmols of Trolox equivalent (TE)/100g FW). Reactivity towards ABTS radical cation and ferric-reducing antioxidant power (FRAP) values were 7580.95?±?97.65 µmols of TE/100g FW and 4383.13?±?95.30?μmol of TE/100g FW, respectively. The latex exhibited also significant inhibition of acetylcholinesterase activity with an IC₅₀ value of 4.46 µg/mL (C.L.?=?2.002–9.947). Furthermore, Brine shrimp (Artemia salina) cytotoxicity bioassay showed that the larvae viability was significantly affected at higher concentrations than those capable to induce significant antioxidant and anti-acetylcholinesterase effects (LD₅₀ 25 µg/mL). The results suggest that polyphenols and terpenoids can contribute significantly to antioxidant and anti-acetylcholinesterase activities of E. dendroides latex.     

红花桑寄生叶提取物的抗氧化活性及酚类物质分析

采用DPPH法、TEAC法、FRAP法对红花桑寄生叶不同溶剂提取物的抗氧化活性进行体外评价,并测定其总酚、总黄酮含量。结果表明,溶剂种类对红花桑寄生叶提取物的得率、总酚、总黄酮及抗氧化活性影响显著。在3种评价方法中,不同溶剂提取物的抗氧化活性均表现出不同程度的量效依赖关系。3种溶剂提取物的抗氧化活性强弱依次为丙酮提取物 >甲醇提取物 >水提取物,其中80%丙酮提取物(总酚含量最高,达276.83mg/g)抗氧化活性最强,清除DPPH自由基能力EC₅₀值为0.247,FRAP值(FeSO₄ mmol/100g)为115.81,浓度为1.0mg/ml时,TEAC值为2.04。     

Tentative Identification of Phytochemicals and Antioxidant Activities during Fruit-Ripening on <i>Chamaedorea radicalis</i> Mart.

This work aims to determine the phytochemical characterization of the pericarp of Chamaedorea radicalis Mart. fruit as a non-timber product with potential to obtain phytochemicals with potential applications in the industry. Fruit from C. radicalis were grouped in four ripening stages named as S1, S2, S3 and S4, according to maturity; S1 the most unripe stage and S4 the completely ripe stage. Determinations of total phenolic compounds, free radical scavenging activities and total flavonoid contents using spectrophotometric methods were done. Also, the tentative identification of phytochemicals during fruit ripening was done using UPLC-MS-MS. Total phenolic compound (TPC) content ranged from 7.24 to 12.53 mg gallic acid equivalents per gram of fresh weight (mg GAE/ g FW). Total flavonoids (TF) contents ranged from 0.163 to 0.23 mg of quercetin equivalents per g FW (mg QE/g FW). Free radical scavenging activity against DPPH and ABTS radicals varied from 40.80 to 53.68 and from 22.29 to 37.76 mmol Trolox equivalents g FW (mmol TE/g FW), respectively. Antioxidant assay in vitro by FRAP (ferric reducing antioxidant power) method showed that S3 was the highest level with antioxidant power while S4 was the lowest with Red ripeness stage showed the lowest contents for all determinations. Mass spectrometry allowed detection of 26 compounds, including phenolics, alkaloids and saponins. Afzelin, Kaempferol 3-neohesperidoside and the four saponins identified were present in all ripeness stages. Preliminary phytochemical identi- fication and the spectrophotometric determinations showed that the pericarp of C. radicalis presented antioxidants and compounds related to alkaloids, phenolics and saponins. The presence and abundance of each phytochemical regarding each ripeness stage should be considered.     

Variation in phenolic compounds and antioxidant activity in apple seeds of seven cultivars

Polyphenols are the predominant ingredients in apple seeds. However, few data are available on the phenolic profile or antioxidant activity in apple seeds in previous researches. In this study, low-molecular-weight phenolic compounds and antioxidant activity in seeds, peels, and flesh of seven apple cultivars grown in northwest China were measured and analyzed using HPLC and FRAP, DPPH, ABTS assays, respectively. HPLC analysis revealed phloridzin as the dominant phenolic compound in the seeds with its contents being 240.45–864.42 mg/100 gDW. Total phenolic content (TPC) measured by the Folin–Ciocalteu assay in apple seed extracts of seven cultivars ranged from 5.74 (Golden Delicious) to 17.44 (Honeycrisp) mgGAE/gDW. Apple seeds showed higher antioxidant activity than peels or flesh; antioxidant activity in seeds varied from 57.59 to 397.70 μM Trolox equivalents (TE)/g FW for FRAP, from 37.56 to 64.31 μM TE/g FW for DPPH, and from 220.52 to 708.02 μM TE/g FW for ABTS. TPC in apple seeds was significantly correlated with all three assays. Principal component analysis (PCA) indicated that Honeycrisp was characterized with high contents of total polyphenols and phloridzin. Our findings suggest that phenolic extracts from apple seeds have good commercial potential as a promising antioxidant for use in food or cosmetics.     

Antioxidant activity and phenolic compounds of 112 traditional Chinese medicinal plants associated with anticancer

Cancer prevention and treatment using traditional Chinese medicines have attracted increasing interest. This study characterizes antioxidant activity and phenolic compounds of traditional Chinese medicinal plants associated with anticancer, comprising 112 species from 50 plant families. The improved ABTS(*+) method was used to systematically assess the total antioxidant capacity (Trolox equivalent antioxidant capacity, TEAC) of the medicinal extracts. The TEAC values and total phenolic content for methanolic extracts of herbs ranged from 46.7 to 17,323 micromol Trolox equivalent/100 g dry weight (DW), and from 0.22 to 50.3 g of gallic acid equivalent/100 g DW, respectively. A positive, significant linear relationship between antioxidant activity and total phenolic content (all R(2) values>/=0.95) showed that phenolic compounds were the dominant antioxidant components in the tested medicinal herbs. Major types of phenolic compounds from most of the tested herbs were preliminarily identified and analyzed, and mainly included phenolic acids, flavonoids, tannins, coumarins, lignans, quinones, stilbenes, and curcuminoids. These medicinal herbs exhibited far stronger antioxidant activity and contained significantly higher levels of phenolics than common vegetables and fruits. Traditional Chinese medicinal plants associated with anticancer might be potential sources of potent natural antioxidants and beneficial chemopreventive agents.     

Characterization of the phenolic constituents in Mauritian endemic plants as determinants of their antioxidant activities in vitro

The phenolic constituents of Mauritian endemic plants from the Rubiaceae and Myrtaceae family were assessed and correlated with their potential antioxidant activities in vitro. The antioxidant activities of the plant extracts ranged from 0.27 to 1.49mmol Trolox equivalent/g FW and from 0.20 to 1.39mmol Fe(II) equivalent/g FW in the TEAC and FAP assays, respectively, with Syzygium commersonii showing the highest activity in these two systems. Eugenia orbiculata and all the Syzygium species were effective scavengers of hypochlorous acid while Monimiastrum acutisepalum was the most potent inhibitor of deoxyribose degradation. The plant extracts inhibited microsomal lipid peroxidation with low IC(50)s ranging from 0.02 to 1.75mgFW/mL when reaction was initiated with Fe(3+)/ascorbate and from 0.093 to 1.55mgFW/mL in the AAPH-dependent lipid peroxidation. The potential prooxidant nature of the plant extracts was compared with ascorbate (250microM) using copper-phenanthroline assay. The plant extracts at concentrations up to 5gFW/L were not prooxidant. However, Myonima nitens, Syzygium commersonii, Syzygium glomeratum and Syzygium mauritianum at concentrations of 10gFW/L had potency approaching 50% of the prooxidant activity of ascorbic acid in vitro, suggesting relative safeties. The total phenolics influenced the antioxidant activities in the TEAC, FRAP and HOCl scavenging assays whereas a negative correlation was observed with the deoxyribose assay. The high levels of polyphenolic compounds and the significant antioxidant activities of these Rubiaceae and Myrtaceae plant family make them suitable candidates as prophylactic agent.     

Comparative antioxidant-capacity and -content of leaves, bulbs, roots, flowers and fruit of Gethyllis multifolia L. Bolus and G. villosa Thunb. species

The total polyphenol, oxygen radical absorbance capacity (ORAC), ferric reducing antioxidant power (FRAP), radical cation scavenging ability, flavonol and flavanone contents were measured in the leaves, bulbs, roots, flowers and fruit (dry weight) of two natural populations of Gethyllis multifolia (Kukumakranka) and Gethyllis villosa. The flowers and fruit of G. multifolia and G. villosa showed higher, and in some cases significantly (P < 0.05) higher antioxidant activities when compared to the leaves, bulbs and roots. This, however, was not true for the flavanone content in both species. The total polyphenol content in the fruits of G. multifolia (21.54 mg GAE/g) and G. villosa (27.64 mg GAE/g) were found to be in agreement with those of raisins (28.30 mg GAE/g), blueberries (24 mg GAE/g) and strawberries (15.40 mg GAE/g). The FRAP values of G. multifolia flowers (76.66 μmole AAE/g) and fruit (91.51 μmole AAE/g) were found to be significantly (P < 0.05) higher than those of the other plant parts (16.76 to 39.08 μmol AAE/g). On the other hand, the flowers (590.23 μmol TE/g) and fruit (741.16 μmol TE/g) of G. villosa revealed a significantly (P < 0.05) higher ORAC when compared to the other plant parts (251.25 to 410.60 μmol TE/g). A strong correlation was evident in the fruit of both species between the total polyphenols and FRAP (r = 0.95), ORAC (r = 0.95) and flavonol content (r = 0.79).     

Phytochemical Profiles and Antioxidant Activities in Six Species of Ramie Leaves

Increased consumption of vegetables or plant food has been associated with decreased risk of developing major chronic diseases, such as cancers, diabetes, cardiovascular diseases, and age-related functional decline. Ramie leaves are rich in phenolics and flavonoids, which have been suggested for human health benefits. Phenolic contents, flavonoid contents, phenolic compounds, and anti-cancer properties in six species of ramie leaves were analyzed by Folin-reagent method, sodium borohydride/chloranil-based assay (SBC), HPLC method and antiproliferation, cytoxicity, respectively. Antioxidant activities were measured through peroxyl radical scavenging capacity (PSC) method, oxygen radical absorbance capacity (ORAC) method, and cellular antioxidant activity (CAA). Research indicated that Boehmeria penduliflora contained the highest total phenolic content (2313.7±27.28 mg GAE/100 g FW), and flavonoid content (1682.4±27.70 mg CAE/100 g FW). Boehmeria tricuspis showed the highest PSC value (9574.8±117.63 µM vit. C equiv./100 g FW), while Boehmeria penduliflora indicated the highest ORAC value (330.44±16.88 µmol Trolox equiv./g FW). The antioxidant activities were correlated with phenolic contents and flavonoid contents. Boehmeria tricuspis had the highest antiproliferative capacity with the lowest EC₅₀ (4.11±0.19 mg/mL). The results for the analyzed ramie for CAA were significantly different from each other (p<0.05), Boehmeria tricuspis had the highest CAA value (133.63±7.10 µmol QE/100 g). Benzoic acid, 4-coumaric acid, caffeic acid, and ferulic acid were the dominant phenolic ingredients in the ramie leaves according to HPLC analysis. Our research is the first report to study the phytochemical profiles and antioxidant activities in different species of ramie leaves for their health benefit.     

Assessment of the polyphenolic composition of the organic extracts of Mauritian black teas: a potential contributor to their antioxidant functions

There is increasing interest in the emerging view that tea improves the antioxidant status in vivo and thereby helps to lower risk of certain types of cancer, coronary heart disease and stroke and its component biofactors could provide prophylactic potential for these diseases. The polyphenolic composition and the antioxidant properties of organic extracts (acetone/methanol) of Mauritian commercial black teas were evaluated. HPLC data of the individual compounds revealed remarkably high levels (+)-Catechin ((+)-C), (-)-epicatechin ((-)-EC), (-)-epicatechin 3-gallate ((-)-ECG), (-)-epigallocatechin ((-)-EGC), (-)-epigallocatechin 3-gallate ((-)-EGCG) and gallic acid. Analysis of hydrolysed extracts indicated that quercetin was the dominant flavonol aglycone with traces of myricetin and kaempferol. Based on the Ferric Reducing Antioxidant Power (FRAP) and the Trolox Equivalent Antioxidant Capacity (TEAC) assays Extra tea from Bois Chéri exhibited the highest antioxidant potential. Linear regression analyses showed that the antioxidant capacities of the organic extracts are strongly influenced by total phenols (TEAC: r=0.95 and FRAP: r=0.96) and to a lesser extent by total proanthocyanidin and total flavonoid contents. Catechins and gallic acid seem to add up to the overall antioxidant capacity of black tea extracts. The fresh tea leaves had high levels of total phenols, total flavonoids, total proanthocyanidin and exhibited greater antioxidant potential when compared with black teas. Organic extracts of endemic teas represent useful source of phenolic antioxidants supplements for prophylactic use.     

Comparison of antioxidant capacity and phenolic compounds of berries, chokecherry and seabuckthorn

Antioxidant capacity and phenolic compounds (phenolic acids and anthocyanins) of four berry fruits (strawberry, Saskatoon berry, raspberry and wild blueberry), chokecherry and seabuckthorn were compared in the present study. Total phenolic content and total anthocyanin content ranged from 22.83 to 131.88 g/kg and 3.51 to 13.13 g/kg, respectively. 2,2-Diphenyl-1-picryhydrazyl free radical scavenging activity ranged from 29.97 to 78.86%. Chokecherry had the highest antioxidant capacity when compared with berry fruits and seabuckthorn. The highest caffeic acid, gallic acid and trans-cinnamic acid levels were found in chokecherry (6455 mg/kg), raspberry (1129 mg/kg) and strawberry (566 mg/kg), respectively. Caffeic acid was also the major phenolic acid in Saskatoon berry (2088 mg/kg) and wild blueberry (1473 mg/kg). The findings that chokecherry has very high antioxidant capacity and caffeic acid levels, are useful for developing novel value-added antioxidant products and also provide evidence essential for breeding novel cultivars of fruit plants with strong natural antioxidants.     

Phenolics as potential antioxidant therapeutic agents: mechanism and actions

Accumulating chemical, biochemical, clinical and epidemiological evidence supports the chemoprotective effects of phenolic antioxidants against oxidative stress-mediated disorders. The pharmacological actions of phenolic antioxidants stem mainly from their free radical scavenging and metal chelating properties as well as their effects on cell signaling pathways and on gene expression. The antioxidant capacities of phenolic compounds that are widely distributed in plant-based diets were assessed by the Trolox equivalent antioxidant capacity (TEAC), the ferric reducing antioxidant power (FRAP), the hypochlorite scavenging capacity, the deoxyribose method and the copper-phenanthroline-dependent DNA oxidation assays. Based on the TEAC, FRAP and hypochlorite scavenging data, the observed activity order was: procyanidin dimer > flavanol > flavonol > hydroxycinnamic acids > simple phenolic acids. Among the flavonol aglycones, the antioxidant propensities decrease in the order quercetin, myricetin and kaempferol. Gallic acid and rosmarinic acid were the most potent antioxidants among the simple phenolic and hydroxycinnamic acids, respectively. Ferulic acid displayed the highest inhibitory activity against deoxyribose degradation but no structure–activity relationship could be established for the activities of the phenolic compounds in the deoxyribose assay. The efficacies of the phenolic compounds differ depending on the mechanism of antioxidant action in the respective assay used, with procyanidin dimers and flavan-3-ols showing very potent activities in most of the systems tested. Compared to the physiologically active (glutathione, -tocopherol, ergothioneine) and synthetic (Trolox, BHA, BHT) antioxidants, these compounds exhibited much higher efficacy. Plant-derived phenolics represents good sources of natural antioxidants, however, further investigation on the molecular mechanism of action of these phytochemicals is crucial to the evaluation of their potential as prophylactic agents.     

Caesalpinia palmeri: First Report on the Phenolic Compounds Profile,Antioxidant and Cytotoxicity Effect

This study aimed to determine the phenolic compounds profile, antioxidant potential and cytotoxicity of extracts and fractions of Caesalpinia palmeri. Methanolic extracts were generated from C. palmeri berries, stems and flowers. The latter was subjected to liquid-liquid partition, obtaining hexane, ethyl acetate and residues fractions. Results showed that the flower extract and ethyl acetate fraction had a larger concentration of phenolic compounds (148.9 and 307.9 mg GAE/g, respectively), being ellagic acid (6233.57 and 19550.08 μg/g, respectively), quercetin-3-β-glycoside (3023.85 and 8952.55 μg/g, respectively) and gallic acid (2212.98 and 8422.34 μg/g, respectively) the most abundant compounds. Flower extract and ethyl acetate fraction also presented the highest antioxidant capacity on all tested methods (DPPH, ABTS, ORAC and FRAP) and low cytotoxicity against ARPE-19 cells (IC₅₀ >170 μg/mL). C. palmeri possessed high antioxidant potential, associated with the presence of phenolic compounds and low cytotoxicity, suggesting that they could represent an option to counter oxidative stress.     

The polyphenolic content of fruit and vegetables and their antioxidant activities. What does a serving constitute?

Analysis of the major flavone, flavonol, anthocyanidin and hydroxycinnamic acid constituents (and their glycosides) of onion, tomato, egg plant and apple has been undertaken and the antioxidant activities of the phenolic extracts determined. The major phenolic antioxidant components of egg plant are chlorogenic acid in the flesh and a delphinidin conjugate in the skin. In the case of apple, the major phenolic antioxidants detected are chlorogenic acid, procyanidins/catechin compounds, rutin and phloridzin. Quercetin glycosides are well-known to be the major phenolic components of onion. Assessment of the antioxidant activities of a serving of 100 g fresh weight fruit, vegetable and comparison with previously reported findings for 150 ml beverage (500 ml portion in the case of beer), expressed in μmol Trolox equivalents show that the antioxidant activities of 1 glass (150 ml) red wine ≡ 12 glasses white wine ≡ 2 cups of tea ≡ 4 apples ≡ 5 portions of onion ≡ 5.5 portions egg plant ≡ 3.5 glasses of blackcurrant juice ≡ 3.5 (500 ml) glasses of beer ≡ 7 glasses of orange juice ≡ 20 glasses of apple juice (long life).     

Black Tea Represents a Major Source of Dietary Phenolics Among Regular Tea Drinkers

The phenolic composition and antioxidant activities [TEAC, ORAC, FRAP] of consumer brews (1 tea bag in 230 ml for 1 min) of seven different brands of black tea from the British market were investigated. The main phenolic compounds identified were epigallocatechin gallate, four theaflavins, as well as epicatechin gallate, theogallin (tentative assignment), quercetin-3-rutinoside and 4-caffeoyl quinic acid. Thearubigins represented an estimated 75-82% of the total phenolics. Further, polyphenol fractions were in decreasing order theaflavins, flavan-3-ols, flavonols, gallic acids and hydroxycinnamates. On average, a cup of a consumer brew of black tea is providing polyphenols at the level of 262 mg GAE/serving, of which 65 mg were assigned to individual polyphenols. The antioxidant activity of black tea preparations is higher than that of most reported dietary agents on a daily basis. Correlations were observed between the antioxidant activities and the sum of all quantified polyphenols by HPLC analysis as well as with the total phenolics. Treatment of the black tea brew with simulated gastric juice resulted in a significant increase of the identified theaflavins implying a partial cleavage of thearubigins in the environment of the gastric lumen. Therefore, black tea can be considered to be a rich source of polyphenols and/or antioxidants.     

Antioxidant activities and phenolics content of eight species of seaweeds from north Borneo

The antioxidant activity of eight edible species of Malaysian North Borneo seaweeds obtained from Sabah waters (Kudat, Tanjung Aru and Semporna) consisting of three red seaweeds (Eucheuma cottonii, E. spinosum and Halymenia durvillaei), two green seaweeds (Caulerpa lentillifera and C. racemosa) and three brown seaweeds (Dictyota dichotoma, Sargassum polycystum and Padina sp.) were determined. Methanol and diethyl ether were used as extraction solvent. The antioxidant activities were determined by two methods, TEAC (trolox equivalent antioxidant capacity) and FRAP (ferric reducing antioxidant power) assays. The total phenolic content of the extract was determined according to the Folin–Ciocalteu method and results were expressed as phloroglucinol equivalents. The methanolic extracts of green seaweeds, C. lentillifera and C. racemosa, and the brown seaweed, S. polycystum showed better radical-scavenging and reducing power ability, and higher phenolic content than the other seaweeds. The TEAC and FRAP assays showed positive and significantly high correlation (R ² = 0.89). There was a strong correlation (R ² = 0.96) between the reducing power and the total phenolic content of the seaweeds methanolic dry extracts. These seaweeds could be potential rich sources of natural antioxidants.     

Total antioxidant capacity assay of human serum using copper(II)-neocuproine as chromogenic oxidant: the CUPRAC method

BACKGROUND: Tests measuring the combined antioxidant effect of the nonenzymatic defenses in biological fluids may be useful in providing an index of the organism's capability to counteract reactive species known as prooxidants, resist oxidative damage and combat oxidative stress-related diseases. The selected chromogenic redox reagent for the assay of human serum should be easily accessible, stable, selective, respond to all types of biologically important antioxidants such as ascorbic acid, alpha-tocopherol, beta-carotene, reduced glutathione (GSH), uric acid and bilirubin, regardless of chemical type or hydrophilicity. Currently, there is no rapid method for total antioxidant assay of human serum meeting the above criteria.METHODS: Our recently developed cupric reducing antioxidant capacity (CUPRAC) spectrophotometric method for a number of polyphenols and flavonoids using the copper(II)-neocuproine reagent in ammonium acetate buffer was now applied to a complete series of plasma antioxidants for the assay of total antioxidant capacity (TAC) of serum, and the resulting absorbance at 450 nm was recorded either directly (e.g. for ascorbic acid, alpha-tocopherol and glutathione) or after incubation at 50 degrees C for 20 min (e.g. for uric acid, bilirubin and albumin), quantitation being made by means of a calibration curve. The lipophilic antioxidants, alpha-tocopherol and beta-carotene, were assayed in dichloromethane (DCM). Lipophilic antioxidants of serum were extracted with n-hexane from an ethanolic solution of serum subjected to centrifugation. Hydrophilic antioxidants of serum were assayed after perchloric acid precipitation of proteins in the centrifugate.Results: The molar absorptivities, linear ranges and trolox equivalent antioxidant capacity (TEAC) coefficients of the serum antioxidants were established with respect to the CUPRAC spectrophotometric method, and the results (TEAC, or TEAC coefficients) were evaluated in comparison to the findings of the ABTS/TEAC reference method using persulfate as oxidant. As for hydrophilic phase, a linear correlation existed between the CUPRAC and ABTS findings (r=0.58), contrary to current literature reporting that either serum ORAC or serum ferric reducing antioxidant potency (FRAP) does not correlate at all with serum TEAC. The analytical responses of serum antioxidants were shown to be additive, enabling a TAC assay. The intra- and inter-assay CVs were 0.7 and 1.5%, respectively, for serum.Conclusions: The CUPRAC assay proved to be efficient for glutathione and thiol-type antioxidants, for which the FRAP test was nonresponsive. The findings of CUPRAC completely agreed with those of ABTS-persulfate for lipophilic phase. The additivity of absorbances of all the tested antioxidants confirmed that antioxidants in the CUPRAC test did not chemically interact among each other so as to cause an intensification or quenching of the theoretically expected absorbance. As a distinct advantage over other electron-transfer based assays (e.g. Folin, FRAP, ABTS, DPPH), CUPRAC is superior in regard to its realistic pH close to the physiological pH, favourable redox potential, accessibility and stability of reagents and applicability to lipophilic antioxidants as well as hydrophilic ones.     

Black tea represents a major source of dietary phenolics among regular tea drinkers

The phenolic composition and antioxidant activities [TEAC, ORAC, FRAP] of consumer brews (1 tea bag in 230 ml for 1 min) of seven different brands of black tea from the British market were investigated. The main phenolic compounds identified were epigallocatechin gallate, four theaflavins, as well as epicatechin gallate, theogallin (tentative assignment), quercetin-3-rutinoside and 4-caffeoyl quinic acid. Thearubigins represented an estimated 75-82% of the total phenolics. Further, polyphenol fractions were in decreasing order theaflavins, flavan-3-ols, flavonols, gallic acids and hydroxycinnamates. On average, a cup of a consumer brew of black tea is providing polyphenols at the level of 262 mg GAE/serving, of which 65 mg were assigned to individual polyphenols. The antioxidant activity of black tea preparations is higher than that of most reported dietary agents on a daily basis. Correlations were observed between the antioxidant activities and the sum of all quantified polyphenols by HPLC analysis as well as with the total phenolics. Treatment of the black tea brew with simulated gastric juice resulted in a significant increase of the identified theaflavins implying a partial cleavage of thearubigins in the environment of the gastric lumen. Therefore, black tea can be considered to be a rich source of polyphenols and/or antioxidants.     

Evaluation of plasma antioxidant activity in rats given excess EGCg with reference to endogenous antioxidants concentrations and assay methods

The contribution of (?)-epigallocatechin gallate (EGCg) intake to in vivo antioxidant activity is unclear, even with respect to plasma. In this study, we examined how administration of EGCg contributes to plasma antioxidant activity, relative to its concentration, endogenous antioxidants, and assay methods, namely oxygen radical absorbance capacity (ORAC) and ferric reducing/antioxidant power (FRAP). Administration of EGCg (500?mg/kg) to rats increased plasma EGCg (4μmol/L as free form) and ascorbic acid (1.7-fold), as well as ORAC (1.2-fold) and FRAP (3-fold) values. The increase in plasma ascorbic acid following EGCg administration was accompanied by its relocation from the adrenal glands and lymphocytes into plasma, and was related to the increase in FRAP. Plasma deproteinization and assays in plasma model solutions revealed that protein levels significantly contributed to ORAC values, where <3?μmol/L EGCg in the presence of protein exhibited minimal antioxidant activity, as measured by both FRAP and ORAC. As the concentration of plasma ascorbic acid was not influenced by deproteinization, differences in FRAP values with and without deproteinization were estimated to determine the contribution of enhanced ascorbic acid attributable to EGCg administration. These results will help to understand the points that should be considered when evaluating EGCg antioxidant activity in plasma.