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.     

Phenolic compound composition and antioxidant activity of fruits of Rubus and Prunus species from Croatia

Two fraction, one containing flavonols, flavan-3-ols, phenolic acids and the other containing anthocyanins, were isolated from Rubus (red raspberry, blackberry) and Prunus (sweet cherry, sour cherry) fruits to study their phenol content by HPLC and antioxidant activity using the DPPH test. Raspberries and blackberries were characterised by catechins and ellagic acid derivatives; sour and sweet cherries by phenolic acids. All fruits had relatively high anthocyanin content. Anthocyanins contributed more to the antioxidant activity of all fruits (∼90%) than flavonols, flavan-3-ols and phenolic acids (∼10%). A biphasic reaction was observed between DPPH^• radicals and phenols, with 'fast' and 'slow' scavenging rates which might be important in the biological activity of these fruits. Sour cherries and blackberries which stand out with the highest total phenol content (1416 and 1040 mg kg⁻¹) had also the strongest antioxidant activity (EC₅₀ = 807 and 672 g of fruit per gram of DPPH) and can be considered as good source of dietary phenols.     

Copigmentation,colour and antioxidant activity of single-cultivar red wines

A hundred and thirty-six single-cultivar red wines of different vintages were collected from several wineries in the Canary Islands in order to study the magnitude of the copigmentation phenomenon and the antioxidant activity. The contribution of free anthocyanins, copigmented anthocyanins and polymeric pigments to the colour of wine, as well as the total phenols, the antioxidant activity (2,2-diphenyl-1-picrylhydrazyl, DPPH method) and the chromatic characteristics of the wines were determined. The influence of ageing time and the climatic conditions on these parameters was also studied. The wines made with Merlot, Ruby Cabernet and Syrah cultivars showed the highest parameters of colour, and the largest contribution to the copigmented anthocyanins was from the Ruby Cabernet, Listán negro and Syrah cultivars. The copigmented anthocyanins and the free anthocyanins decrease with the age of the wine, and the antioxidant activity of the samples appears to be related to the total phenol content. An influence of the climatic conditions on colour parameters has been found. The correlation study between parameters suggests that the parameters b* and L* could be used as suitable indicators of evolution or oxidation stage of red wines.     

Characterization of blond and Star Ruby (red) Jaffa grapefruits using antioxidant and electrophoretic methods

Antioxidant and electrophoretic methods were used to characterize the quality differences between blond and Star Ruby (red) grapefruits. Dietary fibre, minerals and trace elements, total polyphenols, anthocyanins, flavonoids, phenolic and ascorbic acids were also determined. The antioxidant potential of red grapefruit was significantly higher than that of the blond fruit (P < 0.05) and correlated well with the total polyphenols (R² from 0.8456 to 0.9711). In both the cultivars studied, thirty‐two electrophoretic bands were detected [sodium dodecyl‐polyacrylamide gel eletrophoresis (SDS‐PAGE)]. The main electrophoretic bands occurred between 20 and 43 kDa in both grapefruits with few minor differences between the varieties. Our findings indicate the following (i) red grapefruit is preferable: it has a higher concentration of bioactive compounds and antioxidant potential than the blond; (ii) 1, 1‐diphenyl‐2‐picrylhydrazyl (DPPH) test is a more sensitive method for the determination of antioxidant potential; (iii) there are some minor differences in electrophoretic patterns; (iv) antioxidant and electrophoretic methods are a good combination for characterization of differences of the same citrus fruits.     

Special quality traits of coloured potato breeding clones: Anthocyanins,soluble phenols and antioxidant capacity

BACKGROUD: Coloured potato varieties rich in anthocyanins are of increasing interest in breeding to upgrade the nutritional quality of tubers. The objective of this study was to examine purple fleshed breeding clones for anthocyanins, soluble phenols and their antioxidant capacity, and to compare them in this respect with purple and white/yellow fleshed potato cultivars. RESULTS: Within the coloured potato group, the breeding clones had the highest contents of anthocyanins, with values ranging from 0.94 to 1.75 g kg^?1 fresh weight. In cultivars and clones with purple flesh the amounts of soluble phenols were 2.6‐times higher than in white/yellow fleshed potatoes. In addition, coloured clones exhibited 4.4‐fold higher antioxidant activity, which was correlated with phenols and anthocyanins. But there were no major differences between the two potato groups in dry matter, starch, crude protein and reducing sugars. CONCLUSIONS: The involvement of purple fleshed potatoes in breeding led to increased anthocyanin and phenol contents of the resulting progeny. The high level of bioactive plant phenols coincided with an enhanced antioxidant activity, known for its positive health effects. Copyright © 2008 Society of Chemical Industry     

Hydrophilic and lipophilic antioxidant activities of grapes

The 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid)/H2O2/horseradish peroxidase (ABTS/H2O2/HRP) decoloration method permits the evaluation of the antioxidant activity of complex food samples. This method is capable of determining both hydrophilic (in buffered media) and lipophilic (in organic media) antioxidant properties in the same sample. Its application to the study of the antioxidant properties of grapes, one white and two black, has permitted us to establish important differences in the antioxidant activity. The black grapes showed higher antioxidant activity than the white variety. The determination of hydrophilic antioxidant activity (HAA) and lipophilic antioxidant activity (LAA) in the three grapes showed that a minor contribution (4-13%) of total antioxidant activity (TAA) was due to LAA in all cases. The experimentally determined HAA could be approximated using the relative contributions of the calculated values of reference compounds (total phenols as gallic acid and anthocyanins as malvidin).     

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.     

Influence of alcoholic fermentation process on antioxidant activity and phenolic levels from mulberries (Morus nigra L.)

The aim of the present study was to evaluate the profile of the phenolic constituents of Morus nigra fruits and their antioxidant activity (DPPH) and to compare their contents before and after fermentation. Antioxidant phenolics of black mulberry (M. nigra L.) samples grown in Galicia (NW Spain) were extracted with methanol/formic acid/water (MFW) and determined by high performance liquid chromatography (HPLC). Two major anthocyanins (cyanidin 3-glucoside and cyanidin 3-rutinoside) and two flavonols (quercetin 3-glucoside and rutin) were isolated, together with caffeic acid and other hydroxycinnamic and ellagic acid derivatives. Their chemical structures were identified by spectral analyses with diode array detection (DAD), but also with alkaline saponification and acid hydrolysis of the mulberry phenolics. Good correlations (r² = 0.6229) were observed among total flavonols contents and the IC₅₀ radical scavenging capacities of mulberry fruits. Anthocyanins are the major flavonoids present in mulberry. It would be expected that anthocyanins contribute significantly to their antioxidant activity; nevertheless, alcohol generated during fermentation may also contribute to antioxidant activity. Our results provide useful antioxidant nutritional information of fresh and fermented mulberry fruits.     

Effect of temperature on antioxidant capacity during drying process of mortiño (Vaccinium meridionale Swartz)

The mortiño fruit (Vaccinium meridionale Swartz) has been recognized as an excellent source of antioxidants, phenolic compounds, and anthocyanins. Drying conditions, particularly temperature, often lead to food quality degradation. The present study investigated the influence of drying temperature (40, 50, and 60°C) on antioxidant activity, anthocyanin, and phenol content of mortiño. Four different thin layer drying models of drying kinetics (Modified page, Newton, Henderson & Pabis and, two-terms) were fitted to the experimental data. For antioxidant capacity determination, oxygen radical absorbance capacity and ferric ion reducing antioxidant power assays were used. The results showed that antioxidant capacity, and phenolic and anthocyanin content all decreased with increasing temperature and drying time. It was observed that phenols and anthocyanins were conserved in greater amounts at 60°C with 34% (5.85 mg gallic acid/g dm) and 32% (2.36 mg Cyanidin-3-glucoside/g dm) preservation of initial content, respectively. Drying kinetics models were compared based on their R² and root mean square error values between the experimental and predicted moisture ratios. The two-terms model was found to satisfactorily describe the drying curves for all temperatures evaluated, with a determination coefficient (R²) above 0.9987 and root mean square error lower than 0.0201.     

Polyphenolic compounds and antioxidant properties of selected China wines

Thirty-seven China wines, produced from different geographical origins, were examined in this study. The antioxidant activity of wines was measured by different analytical methods: oxygen radical absorbance capacity (ORAC), reducing power, 2,2-azino-di-(3-ethylbenzothialozine-sulphonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH·), hydroxyl radical-scavenger activity, superoxide radical-scavenger activity, lipid peroxidation and chelating capacity. Furthermore,total phenols, total flavonoids, total flavanols and total anthocyanins of wines were determined. As expected, the red wines had much higher phenolic content and antioxidant capacity than rosé wines or white wines. Among the red wines, Cabernet Sauvignon and Muscat Hamburg, respectively, represented the wines with the highest and lowest phenolic contents and antioxidant capacity. Among the white wines, Italian Riesling had the lowest phenolic content and antioxidant capacity. Taken together, a close relationship between phenolic contents and antioxidant capacity, for all wines, was observed.     

Flavonoid constituents and their contribution to antioxidant activity in cultivars and hybrids of rabbiteye blueberry (Vaccinium ashei Reade)

Fruit from 42 blueberry (Vaccinium spp.) cultivars, including 36 rabbiteye cultivars (Vaccinium ashei Reade), three V. ashei hybrid derivatives, and three northern highbush (Vaccinium corymbosum L.) standards were evaluated for antioxidant capacity, individual flavonoid content, and the contribution of each identified phenolic compound to total antioxidant activity. Considerable variation was found in flavonoid content, antioxidant activity, and their contribution to total antioxidant activity among cultivars. Among 42 blueberry cultivars, the rabbiteye ‘Early May’ contained the highest amount of chlorogenic acid, myricetin 3-arabinoside, quercetin derivatives, and delphinidin-, cyanidin-, petunidin-, and malvidin-basis anthocyanins. ‘Early May’ cultivar also had the highest antioxidant activity (88.2 μmol TE/g fw). ‘Owen’, ‘Bluegem’, ‘Clara’, Climax’, and ‘Centurion’ were among the other rabbiteye cultivars that also had high levels of flavonoids and antioxidant activities. In contrast, the pink-fruited V. ashei hybrid, ‘Pink Lemonade’, had the lowest content of flavonoids and lowest antioxidant activity. The mean flavonoid content and antioxidant activity of rabbiteye cultivars was higher than those among northern highbush and V. ashei hybrids. The antioxidant activity of V. ashei hybrid derivatives was derived mainly from chlorogenic acid, myricetin, and quercetin, which contributed 62.5% of total antioxidant activity, whereas anthocyanins (malvidin, petunidin, delphinidin, and cyanidin) were the main contributors to the antioxidant activity of rabbiteye cultivars (76.2%) and northern highbush standards (76.8%). Blueberry cultivars identified to have high phenolic content and high antioxidant activity could be used as parents for future blueberry breeding programmes to develop new blueberry cultivars with higher antioxidant activity and further improve human health.     

Comparison of polyphenolic composition and antioxidant activity of wild Italian blueberries and some cultivated varieties

Four varieties of cultivated blueberries (Vaccinium corymbosum) and a wild crop (Vaccinium miyrtillus) originating form the Modena region in Italy (Mirtillo nero dell’Appennino Modenese) and protected by the mark of origin, were examined in order to determine their antioxidant activity as related to their phenolic composition. The antioxidant activity was measured as radical scavenging activity, ferric reducing activity, and by an amperometric method; the total phenolics and total anthocyanins were determined by colorimetric methods; individual anthocyanins were evaluated by HPLC. Results showed that total phenolics and total anthocyanin concentrations were, respectively two fold and three fold higher in the wild fruits, which also had a higher anthocyanin-to-total phenolic ratio. Determination of individual anthocyanins put in evidence some differences between the cultivated and wild varieties, in particular the absence of acylated anthocyanins in wild blueberries. The antioxidant activity was much higher in wild blueberries than in the cultivated ones, and it was more related to the total phenolic rather that to the anthocyanin concentration.     

A systematic survey of antioxidant activity of 30 Chinese medicinal plants using the ferric reducing antioxidant power assay

The antioxidant activities and total phenolic contents of 30 Chinese medicinal plants were evaluated using the ferric reducing antioxidant power assay and the Folin–Ciocalteu method, respectively. The Chinese medicinal plants were extracted by the traditional method, boiling in water and also in 80% methanol. A significant and linear correlation coefficient between the antioxidant activity and the total phenolic content was found in both aqueous (R² = 0.7917) and methanol (R² = 0.7584) extracts. Phenolic compounds are thus a major contributor of antioxidant activity. Comparing the extraction efficiency of the two methods, the boiling water method extracted phenolic compounds more efficiently, and antioxidant activity of the extract was higher. It was found that the Chinese medicinal plants Rhodiola sacra Fu, the stem of Polygonum multiflorum Thunb. and the root of P. multiflorum Thunb. possessed the highest antioxidant activities and thus could be potential rich sources of natural antioxidants.     

Exploring the phytochemical content and the antioxidant potential of Citrus fruits grown in Cyprus

The physicochemical and phytochemical profile as well as the antioxidant properties of the most important Citrus fruits grown in Cyprus [orange (Citrus sinensis, cv. ‘Valencia’), grapefruit (Citrus paradisi, cvs. ‘White Marsh’, ‘Star Ruby’, ‘Rio Red’) and an interspecific hybrid (Citrus reticulata x Citrus sinensis, cv. ‘Mandora’)] were determined. ‘Valencia’ fruit exhibited the highest phenolic, flavonoid and ascorbic acid content, as well as a higher antioxidant potency, followed by ‘Mandora’ fruit and the three grapefruit cultivars. HPLC indicated significant diversity on flavanones among the examined fruits, while LC-MS analysis revealed the presence of hydroxycinnamic acid derivatives, polymethoxyflavones and a furocoumarin. Overall, this study provides supporting evidence for the superiority of ‘Valencia’ orange fruit as an excellent source of bioactive compounds. In addition, to the best of our knowledge, this is the first study thoroughly describing the phytochemical profile of ‘Mandora’ fruit, an interspecific hybrid cultivated in Cyprus.     

Comparative antioxidant activity and 1H NMR profiling of Mediterranean fruit products

In this study the antioxidant activity of methanol extracts obtained from Mediterranean fruit products (prickly pear fruit jam and cream, myrtle berries jam, orange and mandarin-orange marmalades) was evaluated and compared in several in vitro models of oxidative stress. The compositional profile of methanol extracts (carbohydrates, organic acids, amino acids, and main phenolic compounds) was characterized by ¹H NMR spectroscopy and the total phenol content was estimated by the Folin–Ciocalteu procedure. All extracts showed protective effect against thermal-cholesterol degradation, strictly correlated to total phenols. Extracts from prickly pear cream and myrtle berries jam preserved liposomes from Cu^2 +-induced oxidation, inhibiting the reduction of polyunsaturated fatty acids and the increase of malondialdehyde. Extracts from prickly pear cream and citrus marmalades significantly reduced the reactive oxygen species generation induced by tert-butylhydroperoxide in Caco-2 cell culture. The results of this work qualify all tested Mediterranean fruit preserves as a good source of biologically active components with considerable antioxidant potential.     

Evaluation of antioxidant capacity and total phenolic content of different fractions of selected microalgae

In order to identify new sources of safe and inexpensive antioxidants, the antioxidant capacity and total phenolic content of different fractions of 23 microalgae were evaluated, using Trolox equivalent antioxidant capacity assay and the Folin–Ciocalteu method, respectively. The microalgae were extracted using hexane, ethyl acetate and water by a three-step sequential extraction procedure. Most of these microalgae were evaluated for the first time for their antioxidant activities. It was found that the microalgae Synechococcus sp. FACHB 283, Chlamydomonas nivalis and Nostoc ellipsosporum CCAP 1453/17 possessed the highest antioxidant capacities and thus could be potential rich sources of natural antioxidants. In addition, the correlation coefficients between the antioxidant capacities and the phenolic contents were very small in hexane (R² = 0.0075), ethyl acetate (R² = 0.5851) and water (R² = 0.3599) fractions. Thus, phenolic compounds were not a major contributor to the antioxidant capacities of these microalgae. This was very different from many other plant species like fruits, vegetables and medicinal plants. The microalgae could contain different antioxidant compounds from other plants.     

Effect of jam processing and storage on total phenolics, antioxidant activity, and anthocyanins of different fruits

BACKGROUND: Fruits have been widely recognised as an excellent source of bioactive phenolic compounds. The purpose of this study was to evaluate the effect of jam processing of strawberry, cherry, apricot, fig and orange on the total phenolics, antioxidant activity and anthocyanins during 5 months of storage at 25 °C. RESULTS: Fresh strawberry had the highest contents of total phenolics (8503.1 mg GAE kg^?1) followed by cherry, apricot, fig and orange, respectively. Jam processing decreased the total phenolics, antioxidant activity, and anthocyanins of all fruits. Total phenolics of jam during storage decreased only in apricot, fig and orange. Fresh strawberry had the highest antioxidant activity (54.88% inhibition) followed by the other fruits. Antioxidant activity did not change in strawberry during jam storage, while there are reductions in the other fruits were observed. Fresh strawberry had the highest anthocyanins (2323.8 mg cya‐3‐glu kg^?1), followed by cherry and the other fruits, respectively. Results showed only a decrease of anthocyanins and pH in apricot and fig jams during 5 months of storage. CONCLUSION: Despite the reduction of these compounds in jam processing, it is considered a good method to maintain them during 5 months of storage. Copyright © 2011 Society of Chemical Industry     

Application of Mid-infrared Spectroscopy for the Measurement of Several Quality Parameters of Alcoholic Beverages, Wine and Raki

Mid-infrared (IR) spectroscopy, which is a rapid and relatively small amount of waste producing technique, was used to predict several quality parameters of two types of alcoholic beverages, wine and raki. Mid-infrared spectra of red, rose and white wines and a traditional aniseed alcoholic beverage, raki were collected and relations were established between measured chemical parameters (pH, brix, total phenol content, anthocyanin content, titratable acidity, sugar content, electrical conductivity and some colour parameters) of these beverages and their infrared spectra using chemometric techniques. Partial least square regression provided excellent prediction of total phenol (R ²?=?0.97) and anthocyanin contents (R ²?=?0.98) of wine samples and a good prediction of pH (R ²?=?0.9), brix (R ²?=?0.92) and colour intensity (R ²?=?0.93) values were obtained. Brix, total phenol and sugar content of raki samples were also estimated very successfully (R ²?=?0.99) for raki and good prediction was obtained with pH value. Mid-IR spectroscopy in combination with chemometrics could be a promising technique for determination of several quality parameters of alcoholic beverages simultaneously and rapidly.     

Effects of jam processing on anthocyanins and antioxidant capacities of Rubus coreanus Miquel berry

The effects of jam processing on total phenolics, total flavonoids, total anthocyanins, and antioxidant capacities of fresh Rubus coreanus Miquel (bokbunja) fruits at various pH levels were investigated. Aqueous methanol of 80%(v/v) was found to be the most efficient solvent for extracting phenolics in fruits and jams. More than 90% of total phenolics, antioxidant capacities, and total flavonoids were retained after processing, while approximately 35% of total anthocyanins were lost. Among various pH treatments, jams prepared at pH 2.0–3.0 lost 33–35% of total anthocyanins, while treatments at pH 3.5–4.0 degraded 40–48% of total anthocyanins. Among the various treatments between pH 2.0 and 4.0, jam prepared at pH 3 had the highest sensory scores and overall acceptability. The results suggest that jam making with fruits rich in anthocyanins at lower pH may protect bioactive anthocyanins from thermal processing.     

烘焙条件对小粒黑豆中抗氧化组分及抗氧化活性的影响

小粒黑豆的抗氧化作用与其所含有的酚类、花色苷的含量等密切相关,而这些物质在加工过程中会受温度和时间的影响而发生变化。实验以盐池黑豆、府谷小黑豆两种小粒黑豆为材料,分析烘焙处理对其总酚、花色苷含量、总抗氧化能力及1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基、羟自由基（·OH）、超氧阴离子自由基（O2－·）清除能力的影响。结果表明,烘焙对小粒黑豆的抗氧化活性有显著影响,200 ℃条件下烘焙后的总酚含量显著高于100、150 ℃,150 ℃的总酚含量最低;总花色苷含量随着烘焙温度的升高、处理时间的延长而显著减少;·OH清除作用随着烘焙温度的升高而显著降低;烘焙样品的O2－·清除作用显著低于未烘焙样品（P＜0.05）。盐池黑豆、府谷小黑豆的总酚含量、总抗氧化能力以及DPPH自由基、O2－·的清除作用在150 ℃时最低。200 ℃条件下烘焙30 min,盐池黑豆的总酚含量、总抗氧化能力、DPPH自由基清除率最高;府谷小黑豆在200 ℃条件下烘焙40 min,其总酚含量最高,而100 ℃条件下烘焙20 min时的花色苷含量、总抗氧化能力、DPPH自由基清除率最高。