Antioxidants Bound to an Insoluble Food Matrix: Their Analysis,Regeneration Behavior,and Physiological Importance

Dietary antioxidants play an important role in human health by counteracting oxidative stress and preventing chronic diseases. Most common dietary antioxidants in foods are vitamins, carotenoids, phenolic compounds, sulfur‐containing compounds, and neoformed antioxidants. Antioxidants may be present in free soluble or bound insoluble forms in foods. Antioxidants bound to insoluble food matrices have gained the spotlight because they exert their antioxidant effects much longer than free soluble ones. A direct procedure called QUENCHER has been shown to accurately measure the antioxidant capacity of antioxidants bound to insoluble matrices. This procedure overcomes the drawbacks of extraction‐dependent classical assays leading to underestimation of the total antioxidant capacity (TAC) of foods. This review focuses on antioxidants that are found naturally in foods or are formed in foods during processing specifically the antioxidants bound to the insoluble food matrices. The literature gap on the importance of bound antioxidants, their physiological relevance, and methods for measurement of their antioxidant capacity will be filled by this comprehensive review. In particular, chemical properties and health effects of food antioxidants, measurement of the TAC of foods by the QUENCHER method, digestion behavior of bound insoluble antioxidants, and their interactions with free soluble antioxidants are discussed throughout this review.     

Evaluation of antioxidant capacity of some fruit and vegetable foods: efficiency of extraction of a sequence of solvents

All methods for assessing the total antioxidant capacity (TAC) of food samples are strongly affected by the solvents used during extraction. In recent years a sequential solvent extraction procedure utilising water and acetone has been widely used for TAC measurements of foods. To better understand the efficiency of this procedure in terms of the amount of extracted antioxidants and the subsequent measurement of TAC, two vegetables (onion and spinach) and two fruits (orange and tomato) were sequentially extracted with water, acetone and chloroform. Each extract fraction was analysed separately for its content of known antioxidant compounds by specific procedures and for its TAC by the Trolox equivalent antioxidant capacity assay. The results showed that the compounds in the water and acetone extracts were the main contributors to TAC. The chloroform extracts did not contribute to TAC, with the exception of the spinach extract, owing to the presence of low levels of carotenoids. In conclusion, the analysed extraction procedure was more effective for foods rich in water‐soluble antioxidants than for those rich in lipid‐soluble antioxidants. Copyright © 2006 Society of Chemical Industry     

Ascorbate,not urate,modulates the plasma antioxidant capacity after strawberry intake

The consumption of antioxidant-rich foods has already been associated with acute significant increases in plasma total antioxidant capacity (TAC) in humans, but there is no consensus among different literature reports. Furthermore, the acute rise in plasma TAC observed after consumption of several non-berry fruits seems not to be necessarily related to the absorption of dietary antioxidants, such as micronutrients and phenolic substances, but is attributed to the relevant increase of endogenous urate in serum. In this study, we first compared the nutritional quality of strawberry fruits from different genotypes, all cultivated in the same experimental field. Significant genotype-to-genotype differences were observed in the antioxidant capacity and in the vitamin C, folate and phenolic contents of the fruits. Second, in order to investigate the individual effects of the selected strawberry genotypes on the post-prandial plasma antioxidant status in humans, we assessed the acute effects of a single dose of strawberries in healthy subjects. The variation of plasma TAC through the FRAP and TEAC assays, and any eventual changes in ascorbate and urate levels in serum, were measured during the three hours following the strawberry intake. The acute intake of strawberries resulted in a significant increase in plasma FRAP values in all the subjects, independently of the individual TAC baseline levels. Interestingly, the lowest increases in plasma TAC and in serum ascorbate levels were associated with consumption of the nutritionally-poorest cultivars. In addition, significant increases in ascorbate, but not in urate, concentrations were observed in serum. These findings suggested that the fructose-dependent hyperuremic effect, observed after the intake of non-berry fruits, is not responsible for the plasma antioxidant changes following strawberry consumption.     

Processing and cooking effects on chemical,nutritional and functional properties of pasta obtained from selected emmer genotypes

BACKGROUND: Emmer wheat (T. turgidum ssp. dicoccum Schrank) is an old Mediterranean crop grown for centuries and progressively replaced with durum wheat. Although most of its supposed nutritional properties have not yet been scientifically proven, emmer seems to be appreciated for its content of dietary fibre, resistant starch (RS) and antioxidant compounds. The aim of this work was to evaluate the profiles of dietary fibre, starch and antioxidant compounds in raw materials and in semolina of 13 selected emmer lines and their parents (a durum wheat cultivar and an old T. turgidum dicoccum population). Moreover, the cooking effect on functional properties and total antioxidant capacity (TAC) of pasta derived from emmer lines and the in vivo effect of pasta on postprandial glucose response were determined. RESULTS: Processing and cooking affected the dietary fibre content of pasta: the insoluble dietary fibre content was increased, while a slight loss of soluble dietary fibre was observed. Cooking also resulted in a noteworthy increase in amylose and RS content. The antioxidant compounds (i.e., tocols and carotenoids) as well as TAC decreased dramatically after cooking. Pasta obtained with an emmer line significantly lowered the glycaemic index, strengthening the concept of pasta product as a source of functional components in the habitual diet. CONCLUSIONS: The results showed that emmer semolina is suitable for the preparation of pasta with good organoleptic quality and represents a source of RS and fibre, but processing and cooking negatively affected the amount of antioxidant compounds detected in the wholemeal. Copyright © 2008 Society of Chemical Industry     

Total antioxidant capacity of spices, dried fruits, nuts, pulses, cereals and sweets consumed in Italy assessed by three different in vitro assays

With the aim to expand the Italian total antioxidant capacity (TAC) database, the TAC values of 11 spices, 5 dried fruits, 7 sweets, 18 cereal products, 5 pulses, and 6 nuts were determined using three different assays and considering the contribution of bound antioxidant compounds in fiber-rich foods (i. e. cereals, legumes, and nuts). Among spices, saffron displayed the highest antioxidant capacity, whereas among dried fruits, prune exhibited the highest value. The TAC values of all the chocolates analyzed were far higher than the other sweet extracts measured. Among cereal products, whole meal buckwheat and wheat bran had the greatest TAC. Among pulses and nuts, broad bean, lentil and walnuts had the highest antioxidant capacity, whereas chickpeas, pine nuts and peanuts were less effective. The contribution of bound phytochemicals to the overall TAC was relevant in cereals as well as in nuts and pulses. The complete TAC database could be utilized to properly investigate the role of dietary antioxidants in disease prevention.     

Methodology for the determination of biological antioxidant capacity in vitro: a review

One of the effective means of adding value to agricultural produce is the development of functional foods or dietary supplements enriched with antioxidants. This process involves extraction of antioxidant rich fractions from their sources and then testing for antioxidant activity prior to adding these back to the foods or packing into pills or capsules. Ideally, the antioxidant activity should be tested using both in vitro and in vivo techniques but due to the high cost of conducting animal and human feeding trials, many products undergo only in vitro testing. This review describes popular methods commonly used for testing antioxidant activity in vitro, with particular reference to their reliability, efficiency, accessibility and biological relevance. Copyright © 2006 Society of Chemical Industry     

Antioxidant capacity of the Spanish Mediterranean diet

The objective of this work was to determine the total dietary antioxidant capacity (TDAC) of the Spanish Mediterranean diet. The antioxidant capacity of plant foods and beverages included in National food consumption data was determined. TDAC of the Spanish diet was estimated at 6014 and 3549 μmol trolox equivalents by FRAP (ferric reducing antioxidant power) and ABTS (free radical-scavenging capacity) procedures, respectively. About 68% of TDAC came from beverages and 20% from fruits and vegetables, with a very low contribution from cereals. The capacity to inhibit in vitro LDL oxidation of plant foods and beverages was consistent with their antioxidant capacity. The recommended daily intakes of antioxidant vitamins, C and E, represent about 10% of TDAC. Total phenolics intake was estimated as 1171 mg gallic acid/person/day by the Folin–Ciocalteau method. TDAC may be a parameter to be considered in nutritional and epidemiological studies.     

荧光分光光度计测定保健食品总抗氧化能力

目的：建立用荧光分光光度计测定总抗氧化能力的方法。方法：以2,2'- 偶氮二(2- 脒基丙烷)二盐酸盐(AAPH)作为过氧自由基来源,sodium fluorescein(FL)为荧光指示剂,水溶性VE(trolox)为定量标准,荧光值半数衰减时间作为观察指标,测定6 种保健食品的总抗氧化能力。结果：方法的最低检测限为0.22μmol/L,线性回归方程Y=25.432X+2.0625,R2=0.9949,平行性精密度(RSD)3.5%,重复性精密度(RSD)3.9%,加标回收率在90%～104% 之间。结论：用荧光分光光度计可以测定保健食品总抗氧化能力。     

米糠提取物超声辅助提取工艺及抗氧化活性

以乙醇为提取溶剂,采用响应面法对米糠提取物的超声辅助最佳提取工艺进行探讨。米糠提取物的总酚含量及抗氧化活性分别采用Folin-Ciocalteu 法和 Trolox 等价抗氧化能力(TEAC)方法测定。结果表明：总抗氧化活性随着总酚含量的增加而增大,但其活性高低并不完全取决于总酚物质。米糠提取物最佳提取工艺条件为乙醇体积分数90%(V/V),提取温度55℃,提取时间97min。在此条件下,米糠提取物的总酚含量为(2.76 ± 0.17)mg GAE/g米糠(n=3),总抗氧化活性为(2.99 ± 0.24)μmol TEAC/g 米糠(n=3)。     

A Comparative Study of the Analysis of Antioxidant Activities of Liquid Foods Employing Spectrophotometric, Fluorometric, and Chemiluminescent Methods

The antioxidant profile of liquid foods is complex and includes different lipid and water-soluble compounds. These should be considered when assessing total antioxidant capacity (TAC) of these beverages, since it may act synergistically rather than individually. This study describes and compares the use of spectrophotometric methods (Trolox equivalent antioxidant capacity, TEAC and 2,2-diphenyl-1-picrylhydrazyl, DPPH), fluorometric (oxygen radical antioxidant capacity, ORAC), and photochemiluminescence (PCL) for the measurement of the TAC of different liquid foods (fruit juice mixed with milk and vegetables beverage). An evaluation was also made for the influence of certain compounds (ascorbic acid, phenolic compounds, total carotenoids, and tocopherols) with antioxidant capacity that was present in the samples studied. The different methods studied allow the determination of the TAC of the analyzed foods in a precise and accurate way. The TAC values in the studied samples differ from the applied method. An overall antioxidant potency composite index was calculated by assigning each test's equal weight. When an index score was applied, ORAC method had the higher antioxidant capacity values in the analyzed liquid foods in comparison with the other methods. The correlations among the different methods used for the determination of the antioxidant capacity depend on food, that is, mainly due to compounds (lipid and water soluble) of the different food matrix. In addition, ascorbic acid was the main contributor to antioxidant capacity of fruit juice mixed with milk beverages measured with the different methods. However, in vegetables beverages, phenolic compounds were found to correlate more significantly with antioxidant capacity values.     

Antioxidant activity of phenolic compounds: from in vitro results to in vivo evidence

Over last decade an increasing interest for antioxidants in foods has arisen. The healthy properties of antioxidants related to the prevention of degenerative diseases are the main cause of this boom. An antioxidant prevents the oxidation process, the initial step of development of degenerative diseases, cancer and many others. Literature encompasses analytical methodology development to assess antioxidant properties of foods and beverages. The screening of antioxidant activity of foodstuffs is the subject of a large number of articles. Special interest has been addressed to wine, tea and chocolate. However, the crucial key in the prevention of disease is the action these antioxidants exert after their consumption. Studies involving human subjects are scarce due to the requirements of availability of volunteers and conditions to test are limited. This review summarizes data related to in vitro antioxidant activity of foods, emphasizing the main role of phenolic compounds. A critical comparison is realized between the biological significance of these values and the biological significance of in vivo measurements. In addition, the Plasma Antioxidant Capacity is evaluated and selected as biomarker for in vivo antioxidant status of human organism. In a second part, data collected from different intervention studies performed up to date are compiled and discussed. This review summarized data related to in vitro antioxidant activity of foods, emphasizing the main role of phenolic compounds. A critical comparison is realized between the biological significance of these values and the biological significance of in vivo measurements. In addition, the Plasma Antioxidant Capacity is evaluated and selected as biomarker for in vivo antioxidant status of human organism. In a second part, data collected from different intervention studies performed up to date are compiled and discussed. The original contribution of this work is to compile data of Plasma Antioxidant Capacity after dietetic intervention studies taking into account the portion of food ingested. In addition, we calculated the antioxidant compounds content (phenolic content, ascorbic acid, vitamin E and carotenoids) contained in each food ingested to evaluate better their impact in Plasma Antioxidant Capacity. Intervention studies are grouped by the length of intervention and type of food ingested. Results reported in literature reveal that the increment in Plasma Antioxidant Capacity largely depends on analytical method used.     

Evaluation of physicochemical characteristics,nutritional composition and antioxidant capacity of Chinese organic hawthorn berry (Crataegus pinnatifida)

Hawthorn berry (Crataegus pinnatifida), approved as ‘medicine food homology’ fruit by China’s National Health Commission, has been associated with positive effects on human health. In-depth study of nutritional composition and antioxidant capacity can provide basic information on food value of Chinese organic frozen (OFHB)/freeze-dried (OFDHB) hawthorn berries. Higher levels of dietary fibre, pectin, ascorbic acid, mineral and antioxidant capacity were found compared with some common fruits and other species hawthorn. Both OFHB and OFDHB samples have much higher content of potassium (1.02 × 10⁴ and 9.73 × 10³ mg kg⁻¹) than sodium (54.23 and 42.31 mg kg⁻¹). OFDHB had a more desirable ratio (2.68:1) of insoluble/soluble dietary fibre which is suitable for use as a food ingredient. Antioxidant capacity varied considerably depending on the part (peel > pulp) and reaching up to 577.5 µmol Trolox equivalent g⁻¹. OFHB and OFDHB are excellent natural nutrient-dense and antioxidant sources for dietary supplements and functional foods development.     

Comparison of antioxidant capacity and phenolic composition of peel and flesh of some apple varieties

BACKGROUND: Apples contain a large concentration of phenolic compounds, dependent on factors such as cultivar, harvest, storage conditions, and processing. This study aims to identify the essential phenolic compounds present in various apple varieties, to measure their total antioxidant capacity (TAC) with the CUPRAC (cupric ion reducing antioxidant capacity) and ABTS (2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonate)) methods, and to correlate their TAC values with HPLC findings. RESULTS: The order of TAC (mmol Trolox g^?1 fresh weight) of apple peels determined with the CUPRAC method was: Granny Smith > Amasya > Sky Spur > Ervin Spur > King Luscious ≥ Arap Kizi ≥ Lutz Golden. The theoretically calculated TAC values of HPLC‐quantified compounds, with the aid of the combined HPLC‐CUPRAC method, accounted for 18.4–33.5% of the experimentally observed CUPRAC capacity of peel extracts and 19.5–56.3% of flesh extracts, depending on apple variety. CONCLUSION: In synthetic samples of apple antioxidants, the CUPRAC‐TAC values of constituents, identified and analyzed by HPLC, proved to be additive, enabling measurement of the cooperative action of antioxidants using the proposed methodology. Apple peel showed higher contents of phenolics and therefore higher TAC than apple flesh, confirming the health benefit of the consumption of apples together with peel. © 2012 Society of Chemical Industry     

Antioxidant and antiinflammation capacities of some pear cultivars

Abstract: Five commercial pear cultivars were investigated for total phenolics and flavonoids contents, the main phenolic compounds, and their antioxidant and antiinflammation capacities. Four in vitro oxidant and 2 in vivo antiinflammation models were used to evaluate the pharmacological activities of the different pears. The main phenolic compounds were determined by high‐performance liquid chromatography with diode‐array detector, which result indicated that gallic acid ranged from 5.23 to 10.72 μg/g, catechin from 0.41 to 28.83 μg/g, chlorogenic acid from 485.11 to 837.03 μg/g, caffeic acid from 0 to 1.16 μg/g, epicatechin from 6.73 to 131.49 μg/g, and rutin from 0.92 to 104.64 μg/g. The total antioxidant capacity was in descending order: Shuijing > Fengshui > Xuehua > Ya > Xiang pear, which was consistent with the total phenol and flavonoid contents. Thus, the antioxidant capacity of pears may be attributed to their high contents of phenolics and flavonoids. However, the antiinflammation activity was in decreasing order: Xuehua > Xiang > Ya > Fengshui > Shuijing pear, which indicates that compounds other than antioxidants may be responsible for the antiinflammation effect. Practical Application: The importance on antioxidant activities of phenolic compounds in foods and vegetables as natural antioxidants has reached a new high in recent years. In this study, the total phenol and flavonoid contents, and the antioxidant and antiinflammation activities of 5 different types of commercial pears in China were investigated, which may be the experimental basis for the further development and utilization of the pears.     

Antioxidant Modulation of F2-Isoprostanes in Humans: A Systematic Review

F2-isoprostanes are a biomarker of lipid peroxidation, and their measurement has emerged as a reliable approach to assess oxidative stress. However, dietary intervention studies in humans have provided contrasting results following supplementation with antioxidant-rich foods or supplements. In this paper, we have systematically reviewed the evidence about the effect of supplementation with antioxidant-rich foods and galenic antioxidants on isoprostanes levels in humans. Moreover, the association with nonenzymatic antioxidant capacity (NEAC), a biomarker of endogenous antioxidant status, has also been investigated.

MEDLINE database was searched using the terms “(isoprostane* OR isoP OR iso-PGF OR epi-PGF) AND (intervention* OR consumption* OR administration* OR supplementation*),” with limits activated “humans” and “English.” Abstracts and full texts were screened, from which were selected human intervention studies reporting isoprostanes measurement in biological fluids. The total of the studies carried out with antioxidant-rich foods and antioxidant galenic supplements was 113, reporting 154 interventions. Results suggest that dietary antioxidants modulate successfully the levels of isoprostanes in less than 45% of the interventions. A correspondence between the effect on isoprostane and NEAC has been evidenced, and this correspondence suggests the importance of measuring different biomarkers to obtain a better outline of the redox events following supplementation.     

In vitro procedure to predict apparent antioxidant release from wholegrain foods measured using three different analytical methods

Several methods have been applied to the measurement of antioxidants in biological samples. Extraction methods have previously relied on chemical methods which are non‐physiological. This paper reports the use of an in vitro method with enzymatic and fermentation steps, designed to mimic digestion through the gastrointestinal tract, on release of antioxidants from a range of wholegrain foods. A total of 41 samples, (31 raw foods, 10 of which were also analysed after cooking) were analysed using the ferric reducing antioxidant capacity and Trolox equivalent antioxidant capacity methods. Six samples were also measured using the oxygen radical absorption capacity method. The three antioxidant assay methods gave different apparent antioxidant activity trends, and the range of values was dependent on the type of food. The effects of cooking were mainly observed in the early stages of the incubation procedure, suggesting that cooking may destroy soluble antioxidants but not those bound within the food matrix. For all samples, apparent antioxidant release increased during the incubation period, suggesting that antioxidants bound within the food matrix may be released and exert their effects in different regions of the gastrointestinal tract. Copyright © 2005 Society of Chemical Industry     

Strawberry consumption improves plasma antioxidant status and erythrocyte resistance to oxidative haemolysis in humans

Significant increases in the plasma total antioxidant capacity (TAC) have already been reported after acute intake of strawberries. In addition, antihaemolitic effects of strawberry extracts have been recently demonstrated in vitro, revealing that part of the antioxidant properties of strawberry bioactive compounds could lie in their localisation within cell membranes. However, there is a lack of research evidence from in vivo protracted strawberry consumption studies. We carried out a 16-day pilot study where 12 healthy subjects ingested 500 g of antioxidants-rich strawberries daily, and we evaluated the potential effects of fruit consumption on biomarkers of plasma and cellular antioxidant status. A significant increase in fasting plasma TAC and in serum vitamin C concentrations were progressively observed during the period of strawberry supplementation. An enhanced resistance to haemolysis was also observed in both AAPH-treated and untreated erythrocytes, collected during and after the period of strawberry consumption. The results obtained in this work suggest that regular consumption of antioxidant-rich strawberries may exert an improvement on the plasma antioxidant status and an increase on the antihaemolitic defenses of human erythrocytes.     

Nutrition-based health: cell-based bioassays for food antioxidant activity evaluation

Food science has progressively evolved and now there are wide evidences that foods have biological activities that are beyond their classical nutritional value. In this field, the antioxidant activity of pure compounds, food, feed, and dietary supplements has been extensively studied and numerous analytical approaches and assay models have been developed, involving various systems from simple chemical assays to animal models and human studies. This article is an overview of different cell-based models that have been used for testing the antioxidant properties of food, feed, and dietary supplements. Advantages, drawbacks, and technical problems to develop and validate suitable, robust, and high-throughput cell-based bioassays for screening food antioxidant activity will be discussed.     

Use of Diet-tracking Websites as a Resource for Hard-to-Find Food Label Information: An Example Using Specialty Grocery Store Items

Many specialty foods cannot be found in research-focused food databases. However, some nutrient data can be found for many of these foods through individual website searches using brand and store names. Some popular diet-tracking websites contain data for over 3 million foods, data often entered by consumers, based on non-systematic searches. The reliability of these data to guide dietary data entry decisions are unknown. Five popular diet tracking websites were used to compare availability and accuracy of data for food items from a specialty grocery store that are currently unavailable in research-focused food databases.     

Comparison of the 2,2'-azinobis-3-ethylbenzotiazo-line-6-sulfonic acid (ABTS) and ferric reducing anti-oxidant power (FRAP) methods to asses the total antioxidant capacity in extracts of fruit and vegetables

A comparison was made on the use of two spectrophotometric methods, the ferric reducing antioxidant power (FRAP) method and the 2,2'-azinobis-3-ethylbenzotiazoline-6-sulfonic acid (ABTS) method, for the measurement of the total antioxidant capacity (TAC) of plant foods. The correlations of TAC measured by the two methods were highly significant in both water-soluble (r2= 0.90) and water-insoluble extracts (r2= 0.98) from 13 strawberry samples. Also a corresponding comparison of TAC in extracts from 14 plant species showed high correlation coefficients, r2= 0.98 for water-soluble extracts and r2= 0.88 for water-insoluble extracts. The ratio of TAC values obtained with the two methods (ABTS/FRAP) varied between 0.7 and 3.3 for different plant extracts indicating that they contained antioxidants with varying reactivity in the two methods. TACs in six pure antioxidant substances were ranked in the following order by both methods: quercetin > ferulic acid > catechin > rutin > caffeic acid > Trolox = chlorogenic acid. The two methods showed similar TAC values for quercetin, rutin, caffeic acid and chlorogenic acid while ferulic acid and catechin gave higher results with the ABTS method than with the FRAP method, and such differences probably explain the varying ratios of ABTS/FRAP obtained in foods. Regarding storage TAC in water-soluble strawberry extracts stored at -20 or -80 degrees C was stable for at least five months while storage at 4 degrees C decreased the TAC value with 40% during five weeks of storage. The study showed that both the ABTS and FRAP methods can be used for convenient monitoring of the antioxidant capacities in fruit and vegetables, and that different antioxidants had varying reactivity in the two methods.