Effects of copper on the antioxidant activity of olive polyphenols in bulk oil and oil-in-water emulsions

The antioxidant activity and interactions with copper of four olive oil phenolic compounds, namely oleuropein, hydroxytyrosol, 3,4- dihydroxyphenylethanol- elenolic acid ( 1), and 3,4- dihydroxyphenyl-ethanolelenolic acid dialdehyde ( 2), in olive oil and oil- in- water emulsions stored at 60 degrees C were studied. All four phenolic compounds significantly extended the induction time of lipid oxidation in olive oil with the order of activity being hydroxytyrosol > compound 1 > compound 2 > oleuropein > alpha- tocopherol; but in the presence of Cu( II), the stability of oil samples containing phenolic compounds decreased by at least 90%, and the antioxidant activity of hydroxytyrosol and compounds 1 and 2 became similar. In oil- in- water emulsions prepared from olive oil stripped of tocopherols, hydroxytyrosol enhanced the prooxidant effect of copper at pH 5.5 but not at pH 7.4. The stability of samples containing copper at pH 5.5 was not significantly different if oleuropein was present from that of the control. Oleuropein at pH 7.4, and compounds 1 and 2 at both pH values tested, reduced the prooxidant effect of copper. The lower stability and the higher reducing capacity of all compounds at pH 7.4 could not explain the higher stability of emulsions containing phenolic compounds at this pH value. However, mixtures containing hydroxytyrosol or oleuropein with copper showed higher 1,1-diphenyl- 2- picrylhydrazyl radical scavenging activity at pH 7.4 than at pH 5.5. Moreover, the compound 2- copper complex showed higher radical scavenging activity then the uncomplexed compound at pH 5.5. It can be concluded that the formation of a copper complex with radical scavenging activity is a key step in the antioxidant action of the olive oil phenolic compounds in an emulsion containing copper ions.

Characterization of the phytochemicals and antioxidant properties of extracts from Teaw (Cratoxylum formosum Dyer)

The leaves of the Thai vegetable, Teaw (Cratoxylum formosum Dyer) were extracted with ethanol to provide an extract that had antioxidant properties. The composition of the extract was studied by high-performance liquid chromatography with a diode array detector, and by electrospray ionization mass spectrometry. The main antioxidant component (peak 1) was chlorogenic acid, which was present at 60% of the extract. Three minor components were present at 7%, 3% and 2%, and other components that were present at lower concentrations were also observed. Treatment of the Teaw extract with 2,2-diphenyl-1-picrylhydrazyl radical (DPPH center dot) caused a similar reduction in peak area of 55.2-58.1% for chlorogenic acid and the three minor components, indicating that these components had common structural features. Component 2 was identified as dicaffeoylquinic acid, and compounds 3 and 4 were identified as ferulic acid derivatives. The radical-scavenging activity of the Teaw extract was compared with alpha-tocopherol, BHT and chlorogenic acid, using the DPPH center dot and 2,2'-azinobis (3-ethylbenzothialozinesulfonic acid) radical cation (ABTS(center dot+)) assays. The Teaw extract scavenged both free radicals more strongly than did a-tocopherol and BHT, and the activity of the extract was consistent with the concentration of chlorogenic acid that was present, confirming that this component is a major contributor to the antioxidant activity. The acute toxicity of the Teaw leaf extract was investigated in mice, and it was found that the LD50 of the extract was > 32 g/kg. Consequently, this plant is a promising source of a natural food antioxidant. (c) 2006 Elsevier Ltd. All rights reserved.

Antioxidant properties of Teaw (Cratoxylum formosum Dyer) extract in soybean oil and emulsions

The antioxidant activity of an extract from Teaw (Cratoxylum formosum Dyer) leaves was studied in soybean oil and soybean oil-in-water emulsions. Samples containing the extract or reference antioxidants including chlorogenic acid, which comprises 60% of the Teaw extract, were stored at 60 degrees C and analyzed periodically for peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) to allow both hydroperoxides and hydroperoxide degradation products to be monitored. Chlorogenic acid and the Teaw extract were more effective than a-tocopherol in inhibiting lipid oxidation in bulk oil but were less effective in an oil-in-water emulsion in accordance with the polar paradox. The PV/TBARS ratio for oil samples containing chlorogenic acid was higher than for alpha-tocopherol and BHT because chlorogenic acid inhibits both hydroperoxide formation by radical scavenging and hydroperoxide decomposition by metal chelation. The importance of the metal-chelating activity in retarding hydroperoxide decomposition was confirmed by studying the decomposition of oil samples containing added ferric ions. The PV/TBARS ratio was higher for citric acid than for (x-tocopherol in the presence of added ferric chloride, but the order was reversed in samples lacking ferric chloride. Samples containing added chlorogenic acid gave the highest PV/TBARS ratios both in the presence and absence of ferric ions. The PV/TBARS ratios for the samples containing antioxidants fell rapidly to lower values in a soybean oil-in-water emulsion than in the soybean oil. This was due to increased hydroperoxide decomposition in the emulsion at the same PV. The Teaw extract contained 12% oil-soluble components, which contributed to a slightly higher oil-water partition coefficient than that of chlorogenic acid. The antioxidant activity of the aqueous phase of the Teaw extract was reduced more than that of chlorogenic acid by partitioning of the oil-soluble components into oil, which showed that the less-polar components contributed to the antioxidant activity of the Teaw extract in aqueous media.

Antioxidant and tyrosinase inhibitory activity of mango seed kernel by product

The antioxidant and tyrosinase inhibitory properties of extracts of mango seed kernel (Mangifera indica L.), which is normally discarded when the fruit is processed, were studied. Extracts contained phenolic components by a high antioxidant activity, which was assessed in homogeneous solution by the 2,2-diphenyt-1-picrylhydrazyl radical and 2,2'-azinobis (3-ethylbenzothialozinesulfonic acid) radical cation-scavenging assays and in an emulsion with the ferric thiocyanate test. The extracts also possessed tyrosinase inhibitory activity. Drying conditions and extraction solvent were varied, and optimum conditions for preparation of mango seed kernel extract were found to be sun-drying with ethanol extraction at room temperature. Refluxing in acidified ethanol gave an increase in yield and the obtained extract had the highest content of total phenolics, and also was the most effective antioxidant with the highest radical-scavenging, metal-chelating and tyrosinase inhibitory activity. The extracts did not cause acute irritation of rabbit skins. Our study for the first time reveals the high total phenol content, radical-scavenging, metal-chelating and tyrosinase inhibitory activities of the extract from mango seed kernel. This extract may be suitable for use in food, cosmetic, nutraceutical and pharmaceutical applications. (C) 2009 Elsevier Ltd. All rights reserved.

Antioxidant properties of carotenoids in vitro and in vivo

Carotenoids are a class of natural pigments familiar to all through the orange-red to yellow colors of many fruits, vegetables, and flowers, as well as for the provitamin A activity that some of them possess. A body of scientific evidence suggests that carotenoids may scavenge and deactivate free radicals, acting thereby as antioxidants both in food systems (in vitro) and in the human organism (in vivo). Overall, epidemiological evidence links higher carotenoid intakes and tissue concentrations with reduced cancer and cardiovascular disease risk. However, research has also shown that the antioxidant activity of carotenoids may shift to a prooxidant character depending mainly on the biological environment in which they act. A summary of the antioxidant potential of natural carotenoids both in oil model systems and in vivo is presented in this article.

Antioxidant properties of annatto carotenoids

The antioxidant effects of beta-carotene, oil-soluble (bixin) and water-soluble (norbixin) annatto preparations and mixtures of these carotenoids with virgin olive oil polar extract were assessed in bulk olive oil and oil-in-water emulsions stored at 60degreesC. Norbixin was the only carotenoid that inhibited the oxidative deterioration of lipids in both systems. Though bixin and beta-carotene did not retard autoxidation, their mixtures with the polar extract from virgin olive oil enhanced the antioxidant effect of the olive oil extract. Norbixin (2 mM) was of similar activity to delta-tocopherol (0.1 mM) in stored oil. The combination of norbixin with ascorbic acid or ascorbyl palmitate in oil showed a reduction in formation of volatile oxidation products but not in peroxide value, compared with the analogous sample lacking norbixin. In olive oil-in-water emulsions, norbixin (2 mM) reduced hydroperoxide formation to a similar extent as delta-tocopherol (0.1 mM), which in turn was a better antioxidant than alpha-tocopherol. A synergistic effect between norbixin and ascorbic acid or ascorbyl palmitate was observed in the emulsion systems. (C) 2003 Elsevier Ltd. All rights reserved.

Effect of a cellulase treatment on extraction of antioxidant phenols from black currant (Ribes nigrum L.) pomace

The effect of a commercial cellulase preparation on phenol liberation and extraction from black currant pomace was studied. The enzyme used, which was from Trichoderma spp., was an effective "cellulase-hemicellulase" blend with low P-glucosidase activity and various side activities. Enzyme treatment significantly increased plant cell wall polysaccharide degradation as well as increasing the availability of phenols for subsequent methanolic extraction. The release of anthocyanins and other phenols was dependent on reaction parameters, including enzyme dosage, temperature, and time. At 50 degrees C, anthocyanin yields following extraction increased by 44% after 3 h and by 60% after 1.5 h for the lower and higher enzyme/substrate ratio (E/S), respectively. Phenolic acids were more easily released in the hydrolytic mixture (supernatant) and, although a short hydrolysis time was adequate to release hydroxybenzoic acids (HBA), hydroxycinnamic acids (HCA) required longer times. The highest E/S value of 0.16 gave a significant increase of flavonol yields in all samples. The antioxidant capacity of extracts, assessed by scavenging of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation, the oxygen radical absorbance capacity, and the ferric reducing antioxidant potential depended on the concentration and composition of the phenols present.

Bioactive peptides from food proteins: new opportunities and challenges

Food proteins such as milk and soy are a rich source of bioactive peptides. In the last decade, research into this area has intensified and new bioactive peptide sequences have been discovered with a range of apparent biological functions; for example, antihypertensive, antioxidant, and antimicrobial effects and opiate-like qualities have been reported. These peptides could therefore lead to the development of important functional food products and ingredients for the prevention and even treatment of chronic diseases such as cardiovascular disease and cancer. Peptides can be produced by fermentation with dairy starters for instance, and by enzymatic hydrolysis with pancreatic and microbial enzymes. Further purification is typically carried out by membrane filtration and/or chromatographic methods. The production of novel bioactive peptides and their incorporation into functional food products poses several technological challenges as well as regulatory and marketing issues. Proof of efficacy is of paramount importance; this should be verified by conducting appropriate tests in vivo in animals and in humans. In addition, tests for cytotoxicity and allergenicity must be conducted. Despite all of these hurdles, scientific evidence is increasingly demonstrating the health benefits of diet-based disease prevention, and therefore new developments in this area are likely to continue both at the research and the commercialisation level.

Effect of a simulated kilning regime on the profile and antioxidant activity of the free phenolic acids extracted from green malt

Free phenolic acids were extracted from a laboratory-produced sample of green malt. Aliquots of the phenolic acid extract were heated from 25 to 110°C over 27 h, representative of a commercial kilning regime. Samples were taken at regular intervals throughout heating and were assessed for changes in antioxidant activity by both the 2,2(prime)-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical-cation scavenging (ABTS(^•+)) and the ferric-reducing antioxidant potential (FRAP) assays. Changes in the profile of the phenolic acids of the extracts were determined by HPLC. Overall, there was a decrease in both antioxidant activity level and the level of phenolic acids, but as the temperature increased from 80 to 100°C, there was an increase in both the antioxidant activity level and the level of detected phenolic acids.

Effect of heat treatment on the antioxidant activity, color, and free phenolic acid profile of malt

Green malt was kilned at 95 degrees C following two regimens: a standard regimen (SKR) and a rapid regimen (RKR). Both resulting malts were treated further in a tray dryer heated to 120 degrees C, as was green malt previously dried to 65 degrees C (TDR). Each regimen was monitored by determining the color, antioxidant activity (by both ABTS(center dot+) and FRAP methods), and polyphenolic profile. SKR and RKR malts exhibited decreased L* and increased b* values above approximately 80 degrees C. TDR malts changed significantly less, and color did not develop until 110 degrees C, implying that different chemical reactions lead to color in those malts. Antioxidant activity increased progressively with each regimen, although with TDR malts this became significant only at 110-120 degrees C. The RKR malt ABTS(center dot+) values were higher than those of the SKR malt. The main phenolics, that is, ferulic, p-coumaric, and vanillic acids, were monitored throughout heating. Ferulic acid levels increased upon heating to 80 degrees C for SKR and to 70 degrees C for RKR, with subsequent decreases. However, the levels for TDR malts did not increase significantly. The increase in free phenolics early in kilning could be due to enzymatic release of bound phenolics and/or easier extractability due to changes in the matrix. The differences between the kilning regimens used suggest that further modification of the regimens could lead to greater release of bound phenolics with consequent beneficial effects on flavor stability in beer and, more generally, on human health.

Modulation of detoxification enzymes by watercress: in vitro and in vivo investigations in human peripheral blood cells

Epidemiological studies indicate that consumption of cruciferous vegetables (CV) can reduce the risk of cancer. Supposed mechanisms are partly the inhibition of phase I and the induction of phase II enzymes. The aim of this study was to investigate in vitro and in vivo effects of watercress (WC), a member of the CV family, on chemopreventive parameters using human peripheral blood mononuclear cells (PBMC) as surrogate cells. We investigated the hypothesis that WC reduces cancer risk by inducing detoxification enzymes in a genotype-dependent manner. In vitro gene expression and enzyme activity experiments used PBMC incubated with a crude extract from fresh watercress (WCE, 0.1-10 mu L/mL with 8.2 g WC per 1 mL extract) or with one main key compound phenethyl isothiocyanate (PEITC, 1-10 mu M). From an in vivo perspective, gene expression and glutathione S-transferase (GST) polymorphisms were determined in PBMC obtained from a human intervention study in which subjects consumed 85 g WC per day for 8 weeks. The influence of WC consumption on gene expression was determined for detoxification enzymes such as superoxide dismutase 2 (SOD2) and glutathione peroxidase 1 (GPX1), whilst the SOD and GPX activities in red blood cells were also analysed with respect to GST genotypes. In vitro exposure of PBMC to WCE or PEITC (24 h) increased gene expression for both detoxification enzymes GPX1 (5.5-fold, 1 mu L/mL WCE, 3.7-fold 1 mu M PEITC) and SOD2 (12.1-fold, 10 mu L/mL WCE, 7.3-fold, 10 mu M PEITC), and increased SOD2 activity (1.9-fold, 10 mu L/mL WCE). The WC intervention had no significant effect on in vivo PBMC gene expression, as high individual variations were observed. However, a small but significant increase in GPX (p = 0.025) and SOD enzyme activity (p = 0.054) in red blood cells was observed in GSTM1*0, but not in GSTM1*1 individuals, whilst the GSTT1 genotype had no impact. The results indicate that WC is able to modulate the enzymes SOD and GPX in blood cells in vitro and in vivo, and suggest that the capacity of moderate intake of CV to induce detoxification is dependent in part on the GSTM1 genotype.

Influence of habitual diet on antioxidant status: a study in a population of vegetarians and omnivores

Background: Antioxidant status can be used as a biomarker to assess chronic disease risk and diet can modulate antioxidant defence. Objective: To examine effects of vegetarian diet and variations in the habitual intakes of foods and nutrients on blood antioxidants. Subjects and Setting: Thirty-one vegetarians (including six vegans) and 58 omnivores, non-smokers, in Northern Ireland. Design: A diet history method was used to assess habitual diet. Antioxidant vitamins, carotenoids, uric acid, zinc-and ferric-reducing ability of plasma (FRAP) were measured in fasting plasma and activities of glutathione peroxidase (GPX), superoxide dismutase ( SOD) and glutathione S-transferase (GST) and level of reduced glutathione (GSH) were measured in erythrocytes. Results: Vegetarians had approximately 15% higher levels of plasma carotenoids compared with omnivores, including lutein (P <= 0.05), a-cryptoxanthin (P <= 0.05), lycopene (NS), alpha-carotene (NS) and beta-carotene (NS). The levels/activities of all other antioxidants measured were similar between vegetarians and omnivores. Total intake of fruits, vegetables and fruit juices was positively associated with plasma levels of several carotenoids and vitamin C. Intake of vegetables was positively associated with plasma lutein, alpha-cryptoxanthin, alpha-carotene and beta-carotene, whereas intake of fruits was positively associated with plasma beta-cryptoxanthin. Intake of tea and wine was positively associated with FRAP value, whereas intake of herbal tea associated positively with plasma vitamin C. Intakes of meat and fish were positively associated with plasma uric acid and FRAP value. Conclusions: The overall antioxidant status was similar between vegetarians and omnivores. Good correlations were found between intakes of carotenoids and their respective status in blood.

Changes in phenolic composition and antioxidant activity of virgin olive oil during frying

The concentration of hydroxytyrosol (3,4-DHPEA) and its secoiridoid derivatives (3,4-DHPEA-EDA and 3,4-DHPEA-EA) in virgin olive oil decreased rapidly when the oil was repeatedly used for preparing french fries in deep-fat frying operations. At the end of the first frying process (10 min at 180 degreesC), the concentration of the dihydroxyphenol components was reduced to 50-60% of the original value, and after six frying operations only about 10% of the initial components remained. However, tyrosol (p-HPEA) and its derivatives (p-HPEA-EDA and p-HPEA-EA) in the oil were much more stable during 12 frying operations. The reduction in their original concentration was much smaller than that for hydroxytyrosol and its derivatives and showed a roughly linear relationship with the number of frying operations. The antioxidant activity of the phenolic extract measured using the DPPH test rapidly diminished during the first six frying processes, from a total antioxidant activity higher than 740,mumol of Trolox/kg down to less than 250 mumol/kg. On the other hand, the concentration of polar compounds, oxidized triacylglycerol monomers (oxTGs), dimeric TGs, and polymerized TGs rapidly increased from the sixth frying operation onward, when the antioxidant activity of the phenolic extract was very low, and as a consequence the oil was much more susceptible to oxidation. The loss of antioxidant activity in the phenolic fraction due to deep-fat frying was confirmed by the storage oil and oil-in-water emulsions containing added extracts from olive oil used for 12 frying operations.

Antioxidant and cellular activities of anthocyanins and their corresponding vitisins A - studies in platelets, monocytes, and human endothelial cells

During red wine aging, there is a loss of anthocyanins and the formation of various other pigments, so-called vitisins A, which are formed through the chemical interaction of the original anthocyanins with pyruvic acid. The objective of this study was to investigate the antioxidant activities of the most abundant anthocyanins present in red wine (glycosides of delphinidin, petunidin, and malvidin) and their corresponding vitisins A. Anthocyanins exhibited a higher iron reducing as well as 2,2'-azinobis (3-ethyl-benzothiazoline-6-sulfonate) and peroxyl radical scavenging activity than their corresponding vitisins A. Delphinidin showed the highest antioxidant effect of the tested compounds in all of the assays used. Furthermore, we studied the effect of anthocyanins and vitisins A on platelet aggregation and monocyte and endothelial function. Anthocyanins and vitisins did not affect nitric oxide production and tumor necrosis factor-alpha (TNF-alpha) secretion in lipopolysaccharide plus interferon-gamma-activated macrophages. Furthermore, anthocyanins and vitisins did not change collagen-induced platelet aggregation in vitro. However, anthocyanins and to a lesser extent vitisins exhibited protective effects against TNF-alpha-induced monocyte chemoattractant protein production in primary human endothelial cells.

Red wine anthocyanins are rapidly absorbed in humans and affect monocyte chemoattractant protein 1 levels and antioxidant capacity of plasma

Epidemiological studies suggest that a moderate consumption of anthocyanins may be associated with protection against coronary heart disease. The main dietary sources of anthocyanins include red-coloured fruits and red wine. Although dietary anthocyanins comprise a diverse mixture of molecules, little is known how structural diversity relates to their bioavailability and biological function. The aim of the present study was to evaluate the absorption and metabolism of the 3-monoglucosides of delphinidin, cyanidin, petunidin, peonidin and malvidin in humans and to examine both the effect of consuming a red wine extract on plasma antioxidant status and on monocyte chemoattractant protein I production in healthy human subjects. After a 12-h overnight fast, seven healthy volunteers received 12 g of an anthocyanin extract and provided 13 blood samples in the 24 h following the test meal. Furthermore, urine was collected during this 24-h period. Anthocyanins were detected in their intact form in both plasma and urine samples. Other anthocyanin metabolites could also be detected in plasma and urine and were identified as glucuronides of peonidin and malvidin. Anthocyanins and their metabolites appeared in plasma about 30 min after ingestion of the test meal and reached their maximum value around 1.6 h later for glucosides and 2.5 h for glucuronides. Total urinary excretion of red wine anthocyanins was 0.05+/-0.01% of the administered dose within 24 h. About 94% of the excreted anthocyanins was found in urine within 6 h. In spite of the low concentration of anthocyanins found in plasma, an increase in the antioxidant capacity and a decrease in MCP-1 circulating levels in plasma were observed. (C) 2009 Elsevier Inc. All rights reserved.