Peroxidase-based biosensor as a tool for a fast evaluation of antioxidant capacity of tea

Phenol compounds are significant constituents in vegetables and can be correlated with antioxidant capacity of plants. Thus, the relationship between total antioxidant activity (TAA) and total phenol content was evaluated by using a horseradish peroxidase-based biosensor. Antioxidant activities of tea were investigated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging method. The anti-radical activity determined was based on IC₅₀ values (IC₅₀ represents the antioxidant concentration needed to reduce 50% of the initial amount of DPPH). Among the tested samples, black tea showed the best antioxidant effect. TAAs of the investigated tea samples were well correlated with phenol content, the correlation coefficients R being >0.9. According to these observations a simple reading of the biosensor is possible to find the TAA of tea samples, using this correlation.     

Proanthocyanidin profile and antioxidant capacity of Brazilian Vitis vinifera red wines

The free flavan-3-ol and proanthocyanidin (PA) profile and the antioxidant capacity of wines Vitis vinifera L., 2006 and 2007 vintages, from the São Joaquim region, at southern Brazil, are reported here for the first time. Catechin and epicatechin were the two main monomers in the wine samples, followed by gallocatechin and epigallocatechin; and the PA B1 was the main dimer. The terminal units of the PAs were constituted mainly by catechin units, with the co-presence of epicatechin, gallocatechin, epigallocatechin and traces of epicatechin gallate. The epicatechin and epigallocatechin units were the main constituents of the extension units of PAs with the co-presence of catechin and epicatechin gallate. The values for the mean degree of polymerisation ranged from 4.9 to 9.8. The wine samples demonstrated effective scavenging activity against DPPH and ABTS radicals and against lipid peroxidation in vitro. A positive correlation existed between flavan-3-ol content and antioxidant capacity in vitro.     

An integrated approach to evaluate food antioxidant capacity

ABSTRACT:  Many methods are available for determining food antioxidant capacity, which is an important topic in food and nutrition research and marketing. However, the results and inferences from different methods may vary substantially because each complex chemical reaction generates unique values. To get a complete and dynamic picture of the ranking of food antioxidant capacity, relative antioxidant capacity index (RACI), a hypothetical concept, is created from the perspective of statistics by integrating the antioxidant capacity values generated from different in vitro methods. RACI is the mean value of standard scores transformed from the initial data generated with different methods for each food item. By comparing the antioxidant capacity of 20 commonly consumed vegetables in the U.S. market that were measured with 7 chemical methods, we demonstrated that the RACI correlated strongly with each method. The significant correlation of RACI with an independent data set further confirmed that RACI is a valid tool to assess food antioxidant capacity. The key advantage of this integrated approach is that RACI is in a numerical scale with no units and has consistent agreement with chemical methods. Although it is a relative index and may not represent a specific antioxidant property of different food items, RACI provides a reasonably accurate rank of antioxidant capacity among foods. Therefore, it can be used as an integrated approach to evaluate food antioxidant capacity.     

Comparative study of the antioxidant capacity and polyphenol content of Douro wines by chemical and electrochemical methods

A comparative study of the antioxidant capacity and polyphenols content of Douro wines by chemical (ABTS and Folin–Ciocalteau) and electrochemical methods (cyclic voltammetry and differential pulse voltammetry) was performed. A non-linear correlation between cyclic voltammetric results and ABTS or Folin–Ciocalteau data was obtained if all types of wines (white, muscatel, ruby, tawny and red wines) are grouped together in the same correlation plot. In contrast, a very good linear correlation was observed between the electrochemical antioxidant capacity determined by differential pulse voltammetry and the radical scavenging activity of ABTS. It was also found that the antioxidant capacity of wines evaluated by the electrochemical methods (expressed as gallic acid equivalents) depend on background electrolyte of the gallic acid standards, type of electrochemical signal (current or charge) and electrochemical technique.     

Comparison of chemical composition and antioxidant capacity of commercially available blueberry and blackberry wines in Illinois

Moderate wine consumption may reduce the incidence of certain age-related chronic diseases such as heart disease, hypertension, metabolic disease, and neurodegenerative disease. Blueberry and blackberry wines commercially available in Illinois were evaluated for chemical and quality components relevant to consumers in order to study their potential health benefits. Total polyphenolic content was measured by the Folin-Ciocalteu method, total anthocyanin content by the pH differential test, and in vitro antioxidant capacity (AC) by the oxygen radical absorbance capacity (ORAC) method. Color was measured using Hunter colorimetry and quality parameters including pH, °Brix, acid content, glucose-fructose, and percent alcohol were measured using Fourier transform infrared spectroscopy. Blackberry wines (n= 6) had an average total polyphenolic content of 2212.5 ± 1090.3 mg ellagic acid equivalents (EAE) per liter, total anthocyanin content of 75.56 ± 70.44 mg/L, and AC of 26.39 ± 17.95 mmol trolox equivalents (TEs) per liter. Blueberry wines (n= 4) had an average total polyphenolic content of 1623.3 ± 645.5 mg EAE per liter, total anthocyanin content of 20.82 ± 12.14 mg/L, and AC of 21.21 ± 7.71 mmol TE per liter. Strong positive correlations were found between °Brix and glucose-fructose concentration (r= 0.90), total acid and malic acid (r= 0.90), and between total polyphenols and AC (r= 0.88). The results suggest that fruit wines made from blueberries and blackberries may have potential health applications and therefore could contribute to the economy of the wine industry. PRACTICAL APPLICATION: The majority of wines are produced from grapes, but wine can also be produced from other fruits including blueberries and blackberries, which contain phenolic compounds that may contribute to human health. A comparative evaluation was conducted on commercial nongrape fruit wines and parameters related to their health benefits. Fruit wines made from blueberries and blackberries may have potential health applications and therefore could contribute to the economy of the wine industry.     

Relationship between antioxidant capacity and total phenolic content of red,rosé and white wines

Phenolic compounds are one of the most important quality parameters of wines, since they contribute to wine organoleptic characteristics such as colour, astringency, and bitterness. Furthermore, several studies have pointed out that many show biological properties of interest, related to their antioxidant capacity. This antioxidant activity has been thoroughly studied and a wide variety of methods have been developed to evaluate it.     

Multivariate authentication of the geographical origin of wines: a kernel SVM approach

During the WineDB European project, wine samples from four countries and three different vintages have been collected and their chemical content for 63 parameters was analyzed. The possibility to determine the country of origin of wines based on their chemical content was investigated during the project and the results from two multivariate classification techniques, namely partial least squares-discriminant analysis and kernel support vector machines, are described and compared. Attention has been paid to the development of efficient models in terms of cost of analysis and the problem of variable selection is considered. In particular, the kernel SVM approach leads to models which can reduce the annual updating effort of the classification models since a unique set of parameters can be used to discriminate authentic wines from different countries and different years of production, which is not the case when only PLS-DA is applied.     

Proanthocyanidin content,antioxidant capacity and scavenger activity of Portuguese sparkling wines (Bairrada Appellation of Origin)

BACKGROUND: The main object of the present study was to investigate the different proanthocyanidin fraction (monomeric, oligomeric and polymeric fraction) contents, antioxidant capacity and scavenger activity of the most important and representative commercial sparkling wines available in Bairrada Portuguese Appellation of Origin. RESULTS: The white commercial sparkling wines tested had much less total phenolic, proanthocyanidin content, antioxidant capacity and scavenger activity than the sparkling red wines. For all white and red sparkling wines the polymeric fraction of proanthocyanidins was the most abundant fraction quantified. The antioxidant capacity was positively correlated with the different proanthocyanidin fractions studied. However, in general, higher correlations between total polyphenols, different proanthocyanidin fractions and antioxidant capacity were found only for red sparkling wines. CONCLUSION: The results confirm that Portuguese sparkling wines from Bairrada Appellation of Origin are good sources of antioxidants when compared with other wines elaborated from other grapes varieties and from other regions. At same time, good linear correlations between the levels of each different proanthocyanidin fractions and total polyphenols with antioxidant capacity were found for the commercial sparkling wines analysed. Copyright © 2010 Society of Chemical Industry     

Determination of phenolic composition and antioxidant capacity of native red wines by high performance liquid chromatography and spectrophotometric methods

A reversed-phase high performance chromatographic method for simultaneous determination of 14 phenolic compounds in native red wines was developed in this study. The identified compounds contained gallic acid, (+)-catechin, 3,4-dihydroxybenzoic acid, chlorogenic acid, (?)-epicatechin, 4-hydroxybenzoic acid, syringic acid, caffeic acid, p-coumaric acid, rutin, resveratrol, myricetin, quercetin and kaempferol. The method includes liquid–liquid extraction of acidic pH with ethylacetate. The analysis used a Zorbax Eclipse XDB-C18 column (5 μm, 4.6 mm × 250 mm). The chromatographic separation of these compounds performed in a single run by using the mobile phase gradient elution of methanol water mixture (% 0.2 formic acid) at room temperature, with flow rate at 1 mL/min. Detection was carried out by UV–vis and fluorescence detector. Each analysis required an equilibration period of 10 min and a run time of 14 min for completion. The optimized chromatographic method was carefully validated for precision and accuracy. Our findings indicated that the developed HPLC method was precise, accurate, specific and sensitive for simultaneous determination of phenolic compounds. Consequently, the described method was applied to the analysis of six wines from Malatya and Elaz??. Gallic acid was dominant phenolic acid in red wines. (+)-catechin, (?)-epicatechin and p-coumaric acid were the next most abundant phenolics. The highest level of trans-resveratrol among the red wines was found Buzba?? (Bogazkere–Öküzgözü). The red wines were analyzed for total polyphenol content (TP) by Folin–Ciocalteu (FC) method, using gallic acid as standard. Antioxidant activities (AA) of the red wines were measured using the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. There was a very high correlation between AA and TP in all of the wines tested.     

Effect of co-winemaking in phenolic composition, color and antioxidant capacity of young red wines from La Mancha region

The influence of co-winemaking technique on the phenolic profiles, color and antioxidant capacity of wines made from red grape varieties cultivated in La Mancha region (Spain) was investigated. Co-winemaking red wines were obtained by pre-fermentative blend of grapes (1:1, w/w) from the predominant Cencibel (Tempranillo) variety in this region and the minor varieties Bobal, Moravia Agria, Moravia Dulce, Tortosí and Rojal, together with a three varieties blend (1:1:1, w/w/w) of Cencibel, Bobal and Moravia Agria grapes. The phenolic profiles obtained in co-winemaking wines showed more quantity of different compounds than single-variety wine of Cencibel used as reference. The best results were obtained using Bobal, Moravia Agria and Moravia Dulce varieties for co-winemaking, especially an improvement of color characteristics. All co-winemaking wines significantly increased the total resveratrol content as compared to the Cencibel reference wine, although cis-isomers largely predominated in all wines. Moravia Agria and Rojal varieties produced co-winemaking wines with decreased antioxidant capacity, whereas Bobal and Moravia Dulce varieties increased it, even when the co-winemaking wine from Moravia Dulce contained less total polyphenols than Cencibel reference wine. Co-winemaking technique can be suggested as a way to widen the offer of wines to consumers, incorporating characteristic properties of minor grape varieties. In addition, this enological technique has the benefit of avoiding the disappearance of native species, thus improving the biodiversity of La Mancha region.     

Food antioxidant capacity determined by chemical methods may underestimate the physiological antioxidant capacity

Antioxidant capacity assays are of growing interest in the study of dietary antioxidant properties since they are able to analyse a complex mixture of antioxidants and its synergistic interactions. However, most of the antioxidant capacity assays in the literature are limited by the antioxidant extraction technique, since some antioxidants may remain associated in the extraction residues. The objective of this work was to compare an in vitro physiological procedure for antioxidant extraction with a methanol/acetone/water extraction (chemical procedure). Enzymatic digestions and in vitro colonic fermentations were used on solid plant foods daily consumed in the Spanish diet to estimate the total antioxidant capacity released during the entire digestion process. The in vitro physiological procedure yielded a higher antioxidant capacity than the chemical procedure (7000 and 900 μmol trolox equivalents measured by ABTS, respectively). Our results suggest that determination of antioxidant capacity in food chemical extracts may underestimate the real antioxidant capacity that may be in close contact with the intestinal lumen.     

Ageing impact on the antioxidant and antiproliferative properties of Port wines

This study is focused on the impact of Port wine ageing on some antioxidant features and antiproliferative properties towards human cancer cells. For this, two types of Port wines with different ageing stages were used: a young Vintage and a 20-year-old Tawny. The wines were dealcoholized and two wine phenolic fractions were also characterized and tested. The radical scavenging capacity was similar amongst the wines tested but the reducing capacity was significantly reduced for both Port wine extracts. The results from the FRAP assay, but not DPPH, seem to be positively correlated with the amounts of phenolics with lower structural complexity.MKN-28 (stomach) was found to be the most susceptible cell line to the antiproliferative effect of the young Vintage Port. However, for all wines, Caco-2 (colon) was the cell line that showed the lowest IC₅₀. Interestingly, the old Tawny Port was found to maintain some antiproliferative activity.     

Phenolic compounds and total antioxidant potential of commercial wines

Growing evidence of the role of free radicals and antioxidants in health and ageing has focussed great interest on these compounds. The relationship between the total antioxidant potential and the phenolic content of commercial wines was evaluated. A close relationship between total phenolic content and total antioxidant potential for all wines was observed. Capillary zone electrophoresis showed that, in red wines, gallic acid was the highest of the phenolic acids and (+)-catechin and (−)-epicatechin were the next most abundant phenolics. Also, these compounds were strictly correlated with the total antioxidant potential of wines. Total antioxidant potential, by bleaching of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cations, using gallic acid as standard, could be a practical and simple measurement to evaluate the characteristics of different wines. Furthermore, capillary electrophoresis is a powerful and high-performing tool for evaluating principal antioxidant wine components.     

Phenolic content and antioxidant potential of macerated white wines

Influence of maceration on phenolic content and antiradical activity was analyzed in fourteen white wines from Italian region Friuli–Venezia Giulia and Croatian region Istria. Total phenols were determined by Folin–Ciocalteu reagent, twelve individual polyphenols were determined by high-performance liquid chromatography and antiradical activity was determined using 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH^·). The experiments showed that the maceration process increases significantly the amount of total phenols and inhibition of DPPH^·. Furthermore, a high synergistic activity of individual phenols was observed. The strongest inhibition of DPPH^· and the highest amount of total phenols were obtained for 800 Bianco, a blending macerated wine made from 3 white wine varieties. Our study shows that the antioxidant potential of white grape phenols can be preserved during wine processing. The maceration step allows the extraction of phenolic compounds from grape skins, seeds and stalks, resulting in phenol-rich white wine with strong antioxidant properties.     

Measurements of the in vitro antioxidant activity of German white wines using a novel method

This article provides a study of a new method recently reported and its applicability for the measurements of antioxidant activity of several German white wines. The results obtained are compared with those of a commonly used method, total antioxidant status (TAS) measurements. This new method is based on the inhibitory effects by antioxidants scavengers of free radicals on the Briggs-Rauscher (BR) oscillating reaction. The effect consists of an immediate cessation of the oscillatory regime, an inhibition time that depends linearly on the quantity of the antioxidant added, and subsequent regeneration of oscillations. Sixteen German white wines were tested with the new method, recording potentiometrically the inhibition times produced on an active BR mixture. The different results concerning the ranking order of the antioxidant activity of the examined wines is ascribed to the different pH values at which the two testing methods work. The method based on the BR reaction works in fact at pHƺ, which is similar to that of the fluids in the human stomach while the TAS method works at a pH value near that of the blood (pH=7.4). The mechanism of the antioxidant action of phenols contained in the wines at pHƺ is qualitatively illustrated. The benefits of the novel method are described.     

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