Effect of reddening-ripening on the antioxidant activity of polyphenol extracts from cv. 'Annurca' apple fruits

Apple is among the most consumed fruits worldwide, and several studies suggest that apple polyphenols could play a role in the prevention of degenerative diseases. 'Annurca' apple fruit undergoes, after harvest, a typical reddening treatment to turn the apples' skin red, and it is noted for its high firmness. This paper reports the effect of reddening-ripening treatment on polyphenol concentration and antioxidant activity of both peel and flesh extracts. The in vitro antioxidant properties have been compared with the protective effect against the cytotoxic effects of reactive oxygen species using Caco-2 cells as model system. Pretreatment of cells with different polyphenolic apple extracts provides a remarkable protection against oxidative damage. This effect seems to be associated with the antioxidant activity of 'Annurca' apple polyphenolic compounds. The flesh has antioxidant properties comparable to those possessed by the peel. Neither the reddening nor the fruit conservation causes changes in the antioxidant properties possessed by this apple variety. The data indicate that polyphenolic compounds in 'Annurca' apples are relatively stable in the peel and also in the flesh; therefore, the health benefits of polyphenols should be maintained during long-term storage. Finally, a diet rich in apple antioxidants could exert a beneficial effect in the prevention of intestinal pathologies related to the production of reactive oxygen species.     

Survey of grapevine Vitis vinifera stem polyphenols by liquid chromatography-diode array detection-tandem mass spectrometry

Grapes and red wine prepared from Vitis vinifera L. contain a variety of polyphenols. Some information is available about the polyphenols of the seeds and leaves of grapevine, but considerably less is known about the polyphenols of woody stems. In this paper, we describe the results of a study of polyphenolic compounds in grapevine stems. We demonstrate how a combination of reversed phase high-performance liquid chromatography with ultraviolet-diode array detection and electrospray ionization-tandem mass spectrometry ion-trap detection enables characterization of a phytochemical mixture of considerable complexity. As the polyphenol source, the stems of three frost-hardy grapevine varieties [Hasaine (Hasansky) sladki, Zilga, and Yubilei Novgoroda] were used. The main group of methanol-extractable polyphenols of stems consists of trans-resveratrol and its derivatives including oligomers and glucosides. As minor components of the extract, stilbenoid piceatannol as well as a number of nonstilbenoid polyphenols, mostly flavan-3-ols and phenolic acids glucosides, were determined. The total polyphenol content of the grapevine stems depends on the variety, whereby the stems of cultivar Yubilei Novgoroda with white grapes contain significantly less of both groups of polyphenols.     

Polyphenol composition and antioxidant activity of Kei-apple (Dovyalis caffra) juice

The polyphenolic and ascorbate (ASC) components as well as the antioxidant capacity of Kei-apple (Dovyalis caffra) juice were analyzed and compared to three other fruit juices. The Kei-apple juice had significantly the highest total polyphenolic concentrations (1013 mg gallic acid equivalent/L), and solid phase (C(18)) fractionation identified the majority of these polyphenols to be phenolic acids. The Kei-apple juice also had significantly the highest ASC concentrations (658 mg/L), which showed exceptional heat stability with very little conversion to dehydroascorbate (DHA). Antioxidant capacities of both the unfractionated fruit juices and their solid phase-extracted fractions, as determined by oxygen radical absorbance capacity and ferric reducing antioxidant power analyses, correlated well to the polyphenol concentrations. Gas chromatography-mass spectrometry analyses showed caffeic acid as the most abundant polyphenol present (128.7 mg/L) in the Kei-apple juice; it contributed to 63% of the total antioxidant capacity (of all of the individual compounds identified). Other notable polyphenols identified in higher concentrations included p-coumaric acid, p-hydroxyphenylacetic acid, and protocatechuic acid. Our results therefore support the putative high antioxidant value linked to this fruit and better define this potential in terms of the major antioxidants that exist in the Kei-apple.     

Cultivar and growing region determine the antioxidant polyphenolic concentration and composition of apples grown in New Zealand

Evidence suggests that increasing consumption of fruit and vegetables contributes to improved health and well-being by providing protection from diseases including various cancers and cardiovascular disease. Although there is uncertainty about which components generate this effect, an attractive hypothesis is that the antioxidants are at least partly responsible. We measured the polyphenolic concentrations in 10 different apple cultivars grown commercially in New Zealand, each sourced from three different geographic regions. Our results showed that the concentration of polyphenolics varied among the apple cultivars, with Pacific Queen containing 2.7 times the amount of polyphenolics found in Cox's Orange. Furthermore, there were significant differences in polyphenolic concentrations in fruit from different regions for some cultivars but not for others. We also measured the polyphenolic concentrations in apple skin and flesh and found that on average 46% of the polyphenolics in whole apples were in the skin. Essentially all of the flavonols (quercetin derivatives) were present in the skin. To maximize the intake of apple polyphenols, it is necessary to consume apples of cultivars with high polyphenolic concentrations such as Pacific Queen and include the skin. Our results also showed that there is potential for promoting apple fruit from specific geographical regions because they contained elevated concentrations of antioxidant polyphenolic compounds.     

Polyphenol composition and antioxidant activity in strawberry purees; impact of achene level and storage

In this study the impact of achenes on polyphenolic compounds, ascorbic acids, and antioxidant activities in strawberry purees at production and after storage at 6 and 22 degrees C for 8 and 16 weeks was investigated. Strawberry purees were made from flesh, berry, and achene-enriched homogenate and contained 0, 1.2, and 2.9% achenes, respectively. At production, strawberry purees made from flesh contained more anthocyanins, p-coumaroyl glycosides, and ascorbic acids, whereas increasing achene levels caused increasing levels of ellagic acid derivatives, proanthocyanidins, flavonols, total phenolics (TP), and antioxidant activities. In addition, the anthocyanins, TP, and ferric reducing ability power (FRAP) in purees with more achenes were better retained during storage. Ascorbic acids and anthocyanins declined rapidly during storage, whereas other polyphenols and antioxidant activities were more stable; that is, the contributions from anthocyanins and ascorbic acids to TP and antioxidant activities decreased. The findings that achenes contributed significantly to polyphenol content and stability of strawberry purees may be interesting in a nutritional and, thus, commercial, perspective.     

Polyphenolic composition of hazelnut skin

Skins from different hazelnut samples were characterized for total polyphenol content, total antioxidant capacity (TAC), and their content in specific polyphenolic compounds. The main polyphenolic subclass, identified and quantified by means of HPLC-MS/MS, comprised monomeric and oligomeric flavan-3-ols, which accounted for more than 95% of total polyphenols. Flavonols and dihydrochalcones were 3.5% while phenolic acids were less than 1% of the total identified phenolics. The TAC values of the skin samples ranged between 0.6 and 2.2 mol of reduced iron/kg of sample, which is about 3 times the TAC of whole walnuts, 7-8 times that of dark chocolate, 10 times that of espresso coffee, and 25 times that of blackberries. By describing the profile of polyphenols present in hazelnut skins, this study provides the basis to further investigate the potential health effects of hazelnut byproduct.     

Apple and pear peel and pulp and their influence on plasma lipids and antioxidant potentials in rats fed cholesterol-containing diets

The aim of this study was to assess the bioactive compounds of apple and pear peel and pulp in vitro and their influence on plasma lipids and antioxidant potentials in vivo. The antioxidant potentials measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH), beta-carotene bleaching (beta-carotene), and nitric oxide inhibition radical scavenging (NO) tests in apple peel and pulp were significantly higher than in pear peel and pulp, respectively. The ethanol extract of apple peels showed the strongest inhibition of lipid peroxidation as a function of its concentration and was comparable to the antioxidant activity of butylated hydroxyanisole. The pear pulp extract had the weakest antioxidant ability, whereas other extracts such as apple pulp and pear peel were nearly equal. The antioxidant activities comprised contributions from polyphenols, phenolic acids, and flavonoids and correlated well with polyphenols and flavonoids. The correlation coefficients between polyphenols and antioxidant activities by DPPH, beta-carotene, and NO were as follows: 0.9207, 0.9350, and 0.9453. Contrarily, the correlation coefficient between the content of dietary fiber and the antioxidant activities test was low. The content of all studied indices in apple and pear peel was significantly higher than in peeled fruits (p < 0.05). Diets supplemented with fruit peels exercised a significantly higher positive influence on plasma lipid levels and on plasma antioxidant capacity of rats than diets with fruit pulps.     

Determination of antioxidant activity of wine byproducts and its correlation with polyphenolic content

It has been demonstrated that wine and other products derived from the grape have a high antioxidant capability; as a possible consequence of this, they may have potential benefits for health. The byproducts of the winemaking process represent a source of antioxidant compounds that has been relatively unexploited to date, but that is now the subject of increasing industrial interest. This article describes an approach to the study of the antioxidant activity of grape marcs, stalks, and dregs of both white and red varieties. This activity is compared with the measurements of their content of total polyphenols and of individual polyphenolic compounds, identified and quantified by HPLC. From the results we have been able to establish a positive correlation between the antioxidant activity and the total polyphenolic content of samples, but not with specific compounds.     

Effect of principal polyphenolic components in relation to antioxidant characteristics of aged red wines.

Aged red wines possess significantly different polyphenolic composition compared with young ones, mainly due not only to formation of polymeric compounds but also because of oxidation, hydrolysis, and other transformations that may occur in native grape phenolics during aging. Representative Greek, single-variety, aged red wines were examined for total phenol, total flavanol, and total anthocyanin content using spectrophotometry, and attempts were made to establish correlations with the antiradical, reducing, and hydroxyl free radical scavenging activity. In addition, HPLC analyses were carried out, to ascertain whether individual polyphenols are actually responsible for the antioxidant effects of aged red wines. It was found that total flavanols are the class of polyphenols that account for hydroxyl free radical scavenging efficacy and to a lesser extent for antiradical and reducing ability, whereas there was a less significant link between the antioxidant properties and the total phenolics and only a weak relationship to total anthocyanin content. The correlation of the antioxidant properties with the principal polyphenols showed that individual compounds are weakly associated with all the antioxidant parameters, suggesting that the expression of antioxidant activity in aged red wines is rather a consequence of synergism between various phenolics, and it is not simply attributed to specific constituents.     

Food grade fungal stress on germinating peanut seeds induced phytoalexins and enhanced polyphenolic antioxidants

The effects of food grade fungus Rhizopus oligosporus stress on phytochemicals and phytoalexins of germinating peanut seeds were investigated by comparing the metabolic profiles of ungerminated (UG), germinated (G), and germinated seeds under fungal stress (GS). Three types of peanut seeds with different skin color (red, reddish brown, and black) were compared in the process. The polyphenolic contents were analyzed and correlated with antioxidant capacity for specific free radicals including peroxyl radical ROO(?) (ORAC), hydroxyl radical HO(?) (HORAC), superoxide radical O(2)(?-) (SORAC), and DPPH radical. The polyphenolic fingerprints analyzed by HPLC and LC-MS(n) showed that phenolic acids (coumaric, sinapinic, and ferulic acids derivatives) were the major group of phenolic compounds in ungerminated seeds. G or GS increased the level of phenolic acids, phytoalexins, and antioxidant capacity values in reddish and red peanuts but not in black peanuts. From the LC-MS(n) spectral data, 45 compounds were identified tentatively in the germinated peanuts, including 14 coumaric acids, 3 ferulic acids, 4 sinapinic acids, 2 hydroxybenzoic acids, 1 caffeic acid, 2 flavonoids, and 19 stilbenoids derivatives. Reddish brown germinated peanuts produced the highest amount of phytoalexins after GS with 55 compounds detected. Forty-five of these compounds were suggested as stilbenoid phytoalexins derivatives. The high content of phytoalexins may enhance the bioactivity of peanut seeds as functional food ingredients.     

How to standardize the multiplicity of methods to evaluate natural antioxidants

A great multiplicity of methods has been used to evaluate the activity of natural antioxidants by using different techniques of inducing and catalyzing oxidation and measuring the end point of oxidation for foods and biological systems. Antioxidant in vitro protocols for foods should be based on analyses at relatively low levels of oxidation under mild conditions and on the formation and decomposition of hydroperoxides. For antioxidant in vivo protocols, widely different methods have been used to test the biological protective activity of phenolic compounds. Unfortunately, many of these protocols have been based on questionable methodology to accurately measure oxidative damage and to assess relevant changes in biological targets. Many studies testing the ex vivo activity of phenolic compounds to inhibit human low-density lilpoprotein (LDL) oxidation have been difficult to evaluate because of the structural complexity of LDL particles and because a multitude of markers of oxidative damage have been used. Although studies with animal models of atherosclerosis have demonstrated the antioxidant effect of phenolic compounds in delaying the progress of this disease, human clinical trials of antioxidants have reported inconsistent and mixed results. Complex mixtures of plant polyphenols have been shown to be absorbed to varying degrees as metabolites in the intestine, but little is known about their interactions, bioavailability, and their in vivo antioxidant activity. Several metabolites identified in human plasma after consuming flavonoids need to be tested for possible nonantioxidant activities. More research and better-designed human studies are required to clarify the complex questions of bioavailability of polyphenols and the factors affecting their in vivo activities. Until we know what relevant in vivo activities to measure, any claims on the biological and health protective effects of natural polyphenolic compounds in our diet are premature.     

Effect of Some Extrusion Variables on Residual Quantity of Cyanogenic Compounds in an Organic Breakfast Cereal Containing Passion Fruit Fiber

Organic passion fruit fiber is obtained from organic passion fruit rind and is an interesting source of dietary fiber with potential for use in food products such as breakfast cereals. However, various researchers have confirmed the presence of cyanogenic compounds in passion fruit. The objective of this study was to evaluate the effect of the thermoplastic extrusion process on the residual quantity of total cyanogenic compounds (TCC) in extruded organic breakfast cereal produced with corn flour and different levels of passion fruit fiber added to the formulation. For the production of the extrudates, a 2³ complete factorial design was followed, that permitted the analysis of the results by response surface methodology. The effects of the quantity of passion fruit fiber (0–30%), feed moisture content (18–28%) and barrel temperature (120–160°C) on the residual quantity of TCC were studied. The raw passion fruit fiber presented 748.3 mg/kg of TCC. The extruded products presented TCC contents of 0–254.1 mg/kg, increasing significantly with the increase of the quantity of passion fruit fiber. The residual quantity of TCC was influenced by feed moisture, while temperature had no significant effect on this response. Nevertheless, only a small reduction of cyanogenic compounds was verified in the breakfast cereals produced by thermoplastic extrusion. Thus, it was concluded that the toxicity of the cereal blends was not improved by the extrusion process.     

Identification of two polyphenolic compounds with antioxidant activities in longan pericarp tissues

Longan fruits contain a significant amount of polyphenols. In the present study, polyphenols were extracted from longan pericarp tissues, and then two representative polyphenols were separated and purified by polyamide column chromatography, Sephadex LH-20 column chromatography, and silica gel column chromatography. On the basis of 1H NMR, 13C NMR, and electrospray ionization mass spectrometric (ESI-MS) data, the two compounds were identified as 4-O-methylgallic acid and (-)-epicatechin, respectively. In terms of reaction with longan polyphenol oxidase (PPO), (-)-epicatechin was further identified as the PPO substrate that caused longan fruit to brown. The results of antioxidant activity showed that 4-O-methylgallic acid had higher reducing power and 2,2-diphenyl-1-picrylhydrazyl- (DPPH-), hydroxyl radical-, and superoxide radical-scavenging activities than (-)-epicatechin.     

Identification and quantification of short oligomeric proanthocyanidins and other polyphenols in boysenberry seeds and juice

Proanthocyanidins and other polyphenols in the seeds and juice of boysenberry were quantitatively analyzed. Polyphenolic extracts were prepared from the waste seeds and commercial juice by chromatographic fractionation. Compositional analysis revealed that both extracts contained six polyphenolic classes: flavanol monomers, proanthocyanidins, anthocyanins, ellagic acid, ellagitannins, and flavonol glycosides. Ellagitannins were the most abundant polyphenols in both extracts. Proanthocyanidins were present as short oligomers consisting of dimeric and trimeric procyanidins and propelargonidins, with the most abundant component being procyanidin B4 in both extracts. Quantification by high-performance liquid chromatography-mass spectrometry (HPLC-MS) revealed that the seeds contained a 72-fold higher amount of proanthocyanidins than the juice. These results indicate that boysenberry fruits contain short oligomeric proanthocyanidins along with flavanol monomers and the seeds represent a good source of short oligomeric proanthocyanidins.     

Murta leaves (Ugni molinae Turcz) as a source of antioxidant polyphenols

Extracts from Murta leaves are used by Chilean natives for their benefits on health and cosmetic properties, which are mainly due to the presence of polyphenolic compounds. Extraction of such compounds is strongly influenced by several variables, the effects of which are studied in this work; the antioxidant power of the resulting extracts was measured by two different methods [2,2-diphenyl-1-picrylhydrazyl (DPPH) and thiobarbituric acid reactive substances (TBARS)]. On the whole, maximum values of polyphenolic yields and antiradical power (DPPH method) were attained at 50 degrees C (from 25 to 50 degrees C) and a solvent-to-solid ratio (v/w) of 15:1 (15:1-25:1). The solvents assayed were ethanol, methanol, and water. The highest polyphenolic yield values (2.6% expressed as gallic acid) were reached with methanol, whereas maximum EC50 was attained by the ethanol extract (0.121 mol gallic acid/mol DPPH). Contact time was shown to have only a slight influence in alcoholic extraction, while in water a remarkable effect of increasing contact times (30-90 min) was observed. Just water was the solvent that offered the best result when the antioxidant power was measured by the TBARS method. High-performance liquid chromatography-mass spectrometry analysis revealed the presence of polyphenols, basically flavonols and flavanols, sometimes glycosilated; myricetin and quercetin glycosides were detected in all extracts, whereas epicatechin was present in alcoholic extracts and gallic acid was only present in water.     

Effects of processing steps on the phenolic content and antioxidant activity of beer

A new analytical method (liquid chromatography-antioxidant, LC-AOx) was used that is intended to separate beer polyphenols and to determine the potential antioxidant activity of these constituents after they were allowed to react online with a buffered solution of the radical cation 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(?+)). Using the LC-AOx method, it was possible to demonstrate that the extent of the antioxidant activity was very much dependent on the phenolic compound considered. The method was also applied to the analysis of beer extracts and allowed the evaluation of their antioxidant activity at different steps of beer processing: brewing, boiling, and fermentation. This study showed that the total antioxidant activity remained unchanged throughout beer processing, as opposed to the polyphenolic content, which showed a 3-fold increase. Hopping and fermentation steps were the main causes of this increase. However, the increase measured after fermentation was attributed to a better extraction of polyphenols due to the presence of ethanol, rather than to a real increase in their content. Moreover, this method allowed the detection of three unknown antioxidant compounds, which accounted for 64 ± 4% of the total antioxidant activity of beer and were individually more efficient than caffeic acid and epicatechin.     

Induction of cell death in Caco-2 human colon carcinoma cells by ellagic acid rich fractions from muscadine grapes (Vitis rotundifolia)

Possible anticancer mechanisms exerted by polyphenolic compounds contained in fruits and vegetables include antioxidant activity, the inhibition of proliferation, and the induction of apoptosis in cancer cells. This study examined the effects of four isolated polyphenolic extracts from red muscadine grapes (Vitis rotundifolia) on vital cell parameters and the induction of apoptosis in Caco-2 colon carcinoma cells. The magnitude of effects in cell culture was then correlated to polyphenolic composition and antioxidant capacity. Whereas anticancer effects of individual polyphenolic compounds have been demonstrated multiple times, information relating to anticancer effects of polyphenolic extracts is not available in abundance. All four extracts induced apoptosis, decreased cell number, and caused alterations in cell cycle kinetics in a concentration-dependent manner. The efficacy of the polyphenolics on vital cell parameters correlated well to the presence of ellagic acid glycosides and flavonoids and also to the antioxidant capacity. This study demonstrated the anticancer properties of ellagic acid rich extracts from red muscadine juice.     

Major phytochemicals in apple cultivars: contribution to peroxyl radical trapping efficiency

Forty-one samples of apples (peel plus pulp), obtained from eight cultivars, were examined for concentration of some important phytochemicals and for antioxidant activity expressed as peroxyl radical trapping efficiency. Five major polyphenolic groups plus ascorbate were identified and quantified by HPLC in the apple varieties. Oligomeric and polymeric proanthocyanidins were found to be about two-thirds of total polyphenols. The antioxidant efficiency of the apple extracts and of representative pure compounds for each group of phytochemicals was measured in a micellar system mimicking lipid peroxidation in human plasma. Although the amount of polyphenols measured by HPLC is similar to that measured by standard methods, the antioxidant efficiency calculated on the basis of the contribution of the pure compounds was lower than the antioxidant efficiency of the apple extracts. The higher efficiency of apples appears to be strictly related to the overwhelming presence of oligomeric proanthocyanidins.     

Effect of a polyphenols-enriched chardonnay white wine in diabetic rats

A Chardonnay white wine enriched in polyphenols was obtained by modification of winemaking and characterized by its enrichment in total polyphenolic content (1346 mg/L as compared to 316 mg/L for traditional Chardonnay) and in various individual polyphenols (catechin, epicatechin, procyanidins dimers B1-B4, gallic acid, cafeic acid, and caftaric acid), as determined from HPLC coupled to a diode array detector. The polyphenols-enriched white wine (W) or its ethanol-free derivative (EFW) was then administered by gavage (10 mL/kg, twice a day) for 6 weeks to rats that have been rendered diabetic by a single iv injection of streptozotocin (55 mg/kg). Treatments had no effect on the symptoms associated with hyperglycemia. However, while a reduction in plasma antioxidant capacity was associated with the diabetic state, administration of W or EFW restored plasma antioxidant capacities to a level not significantly different from that of nondiabetic control animals. In addition, the effect of both treatments was manifested by the enlargement of mesenteric arteries, as determined by quantitative histomorphometry. In summary, our study indicates that white wine, when enriched in polyphenols, is able to induce ethanol-independent in vivo effects in a model of insulin-deficient diabetes characterized by a major oxidative stress.     

Two novel dicarboxylic Acid derivatives and a new dimeric hydrolyzable tannin from walnuts

In addition to the 16 previously reported polyphenols including 3 new ellagitannins, 2 novel dicarboxylic acid derivatives, glansreginins A (1) and B (2), and a new dimeric hydrolyzable tannin, glansrin D (3), were isolated, together with 15 known compounds from walnuts, the seeds of Juglans regia. The structures of the new compounds were elucidated on the basis of 1D- and 2D-NMR analyses and chemical data. The antioxidant effect of these isolates was also evaluated by SOD-like and DPPH radical scavenging activities.