Concepción Sánchez-Moreno

A procedure to measure the antiradical efficiency of polyphenols

The kinetic behaviour of polyphenols common in fruits as free radical scavengers was studied using 2,2-diphenyl-1-picrylhydrazyl (DPPH . ). After addition of different standard concentrations to DPPH . (0.025 g litre -1 ), the percentage of remaining DPPH . was determined at different times from the absorbances at 515 nm. The percentage remaining DPPH . against reaction time followed a multiplicative model equation: ln [DPPH . REM ] = b ln t + ln a. The slopes of these equations may be useful parameters to define the antioxidant capacity. The steeper the slope, the lower the amount of antioxidant necessary to decrease by 50% the initial DPPH . concentration (EC 50 ). This parameter, EC 50 , is widely used to measure antioxidant power, but it does not takes into account the reaction time. Time needed to reach the steady state to the concentration corresponding at EC 50 (T EC50 ) was calculated, and antiradical efficiency (AE) was proposed as a new parameter to characterise the antioxidant compounds where AE = 1/EC 50 T EC50 . It was shown that AE is more discriminatory than EC 50 . AE values are more useful because they also take into account the reaction time. The results have shown that the order of the AE (x 10 -3 ) in the compounds tested was: ascorbic acid(11.44) > caffeic acid (2.75) ≥ gallic acid (2.62) > tannic acid (0.57) ≥ DL-α-tocopherol (0.52) > rutin (0.21) ≥ quercetin (0.19) > ferulic acid (0.12) ≥ 3-tert-butyl-4-hydroxyanisole, BHA (0.10) > resveratrol (0.05).

Free radical scavenging capacity and inhibition of lipid oxidation of wines, grape juices and related polyphenolic constituents

Abstract The antioxidant activity of grape juices, wines made from the same lot as juices and their major polyphenolic constituents was measured by the inhibition of lipid oxidation (ferric-thiocyanate) and free radical scavenging (2,2-diphenyl-1-picrylhydrazyl) methods. dl -α-Tocopherol and 3-tertiary-butyl-4-hydroxyanisole (BHA) were used as references. The inhibition of lipid oxidation of the standards followed the order: rutin = ferulic acid > tannic acid = gallic acid = resveratrol > BHA = quercetin > dl -α-tocopherol > caffeic acid. Meanwhile, the free radical scavenging activity of gallic acid was the highest, tannic acid, caffeic acid, quercetin, BHA and rutin activities were intermediate and that for ferulic acid, dl -α-tocopherol and resveratrol were the lowest. Wines had higher activity than the corresponding grape juices and red wine showed the strongest activity among the grape products tested. The antioxidant activity of the samples seems to be based on their free radical scavenging capacity.

Free radical scavenging capacity of selected red, rosé and white wines

The free radical scavenging capacity of selected red, rose and white Spanish wines from different grape varieties was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH·) method using a new methodology developed at our laboratory. The amount of sample necessary to decrease by 50% the initial DPPH· concentration (EC50), the time needed to reach the steady state at EC50 concentration (TEC50) and the antiradical efficiency (AE = 1/EC50TEC50) were determined in the wine samples. Some differences between rose wines made with Garnacha and Tempranillo grape varieties were observed in the UV-vis spectra and in the free radical scavenging parameters, those from Garnacha variety having the highest antioxidant activity. The antiradical efficiency of the wines followed a decreasing order: red wines (22.44 × 10−6) > rose wines (4.90 × 10−6) > white wines (1.88 × 10−6). There was a correlation between antiradical efficiency and total polyphenol (TP): AE = −3.33135 + 0.0180535TP; the correlation coefficient was r = 0.951454. © 1999 Society of Chemical Industry

Evaluation of free radical scavenging of dietary carotenoids by the stable radical 2,2-diphenyl-1-picrylhydrazyl

In order to avoid the interference of compounds with a chromophoric system when the 2,2-diphenyl-1-picrylhydrazyl (DPPH·) method is used, a new measure of the decrease in absorbance at 580 nm was performed (correlation coefficient between absorbance and DPPH· concentration, 0.9979; p < 0.01). The antioxidant effectiveness of dietary carotenes and xanthophylls towards the stable free radical DPPH· was measured. The antioxidant activity expressed as the amount of antioxidant able to reduce the initial DPPH· concentration to 50% (EC50), given in terms of moles of antioxidant per mole of DPPH·, ranged from 0.16 ± 0.01 (lycopene) to 3.29 ± 0.31 (lutein). The parameter antiradical efficiency (AE), which involves the potency (1/EC50) and the time taken to reach the steady state at EC50 (TEC50), was calculated to discriminate carotenoids with no significant difference between their EC50. Comparison of the structures of the carotenoids tested revealed that the scavenging ability towards DPPH· was increased by the length of the effective conjugated double-bond system and was modulated by the addition of chemical groups on the terminal rings (xanthophylls). © 2000 Society of Chemical Industry

Study of low-density lipoprotein oxidizability indexes to measure the antioxidant activity of dietary polyphenols.

Abstract Oxidation of low-density lipoprotein (LDL) may be important in the pathogenesis of atherosclerosis. Recent studies have reported that specific polyphenols play a role as antioxidants inhibiting lipid peroxidation, LDL oxidation and scavenging oxygen radicals. To investigate the mechanism by which dietary antioxidants may reduce the risk of atherosclerosis by inhibiting oxidative damage of lipoproteins, low-density lipoprotein oxidizability indexes were studied to measure the antioxidant activity of dietary polyphenols and a modification in the CLT 50 parameter was proposed. This parameter measure the concentration of antioxidant that increase the Lag time to 50% greater than that of the control, and the proposed modification eliminate the effects of the LDL status in the oxidation induced with Cu 2+ . The lower the CLT 50 , the higher antioxidant activity in the inhibition of LDL oxidation. Polyphenols with different structures such as condensed tannins (tannin acid), flavonols (catechin, quercetin, rutin), cinnamic acids (caffeic and ferulic acid), stilbenes (resveratrol), benzoic acids (gallic acid), anthocyanidins (malvidin); a synthetic phenol (3-tert-butyl-4-hydroxyanisole, BHA) and two vitamins (ascorbic acid - vitamin C- and DL-α-tocopherol -vitamin E-) were studied. All antioxidants tested showed dose-dependent inhibition of LDL oxidation. In general, it was suggested that dietary polyphenols are better antioxidants than other common antioxidants, such as vitamin C and E. An adequate study of the low-density lipoprotein oxidizability indexes could determine the serum antioxidant status within different subjects, and/or evaluate the antioxidant efficiency of different antioxidants in the inhibition of human LDL oxidation.

Potential anti-inflammatory, anti-adhesive, anti/estrogenic, and angiotensin-converting enzyme inhibitory activities of anthocyanins and their gut metabolites

Epidemiological studies have indicated a positive association between the intake of foods rich in anthocyanins and the protection against cardiovascular diseases. Some authors have shown that anthocyanins are degraded by the gut microflora giving rise to the formation of other breakdown metabolites, which could also contribute to anthocyanin health effects. The objective of this study was to evaluate the effects of anthocyanins and their breakdown metabolites, protocatechuic, syringic, gallic, and vanillic acids, on different parameters involved in atherosclerosis, including inflammation, cell adhesion, chemotaxis, endothelial function, estrogenic/anti-estrogenic activity, and angiotensin-converting enzyme (ACE) inhibitory activity. From the assayed metabolites, only protocatechuic acid exhibited a slight inhibitory effect on NO production and TNF-α secretion in LPS-INF-γ-induced macrophages. Gallic acid caused a decrease in the secretion of MCP-1, ICAM-1, and VCAM-1 in endothelial cells. All anthocyanins showed an ACE-inhibitory activity. Delphinidin-3-glucoside, pelargonidin-3-glucoside, and gallic acid showed affinity for ERβ and pelargonidin and peonidin-3-glucosides for ERα. The current data suggest that anthocyanins and their breakdown metabolites may partly provide a protective effect against atherosclerosis that is multi-causal and involves different biochemical pathways. However, the concentrations of anthocyanins and their metabolites, as used in the present cell culture and in vitro assays mediating anti-inflammatory, anti-adhesive, anti-estrogenic, and angiotensin-converting enzyme inhibitory activities, were often manifold higher than those physiologically achievable.

Nutritional Approaches and Health-Related Properties of Plant Foods Processed by High Pressure and Pulsed Electric Fields

Consumers are more and more concerned about the nutritional and health-related characteristics of fruits and vegetables, as well as the safety of the food they eat. The processing of foods is becoming more sophisticated and diverse in response to the growing demand for quality foods. Consumers today expect food products to provide fresh-like appearance, convenience, variety, appropriate shelf-life and caloric content, reasonable cost, environmental soundness, high nutritional and functional quality. Nonthermal processing of fruit and vegetable has been revealed as a useful tool to extend their shelf-life and quality as well as to preserve their nutritional and functional characteristics. In the last ten years, there has been an increasing interest in nonthermal technologies as high pressure processing (HPP) and pulsed electric fields (PEF) to preserve fruit and vegetable products without the quality and nutritional damage caused by heat treatments. This review will contribute to inform many of the studies conducted to obtain a better understanding on the effects of some of these nonthermal processing technologies (high hydrostatic pressure and pulsed electric fields) applied to vegetable foods on their nutritional value and bioactive compounds related to health, including the results on micronutrient bioavailability studies and oxidative stress and inflammation biomarkers. These studies could contribute to select the most appropriate processing parameters to obtain safe, high-quality, nutritional, and functional vegetable food.

Bioaccessibility of tocopherols, carotenoids, and ascorbic acid from milk- and soy-based fruit beverages: influence of food matrix and processing.

A study was made of the effect of high-pressure processing (HPP) and thermal treatment (TT) on plant bioactive compounds (tocopherols, carotenoids, and ascorbic acid) in 12 fruit juice-milk beverages and of how the food matrix [whole milk (JW), skimmed milk (JS), and soy milk (JSy)] modulates their bioaccessibility (%). HPP (400 MPa/40 °C/5 min) produced a significant decrease in carotenoid and ascorbic acid bioaccessibility in all three beverages and maintained the bioaccessibility of tocopherols in JW and JS while decreasing it in JSy. TT (90 °C/30 s) produced a significant decrease in tocopherol and carotenoid bioaccessibility in all three beverages and increased the bioaccessibility of ascorbic acid. With regard to the food matrix, α-tocopherol and ascorbic acid bioaccessibility was greatest in JW beverages and lowest in JSy beverages, whereas no significant differences were found among the three beverages in terms of carotenoid bioaccessibility. HPP-treated samples showed higher tocopherol and carotenoid bioaccessibility than TT-treated samples, thus indicating that HPP combined with a milk matrix positively modulates the bioaccessibility of certain types of bioactive components of food, mainly those of a lipophilic nature.

Stroke: roles of B vitamins, homocysteine and antioxidants

In the present review concerning stroke, we evaluate the roles of B vitamins, homocysteine and antioxidant vitamins. Stroke is a leading cause of death in developed countries. However, current therapeutic strategies for stroke have been largely unsuccessful. Several studies have reported important benefits on reducing the risk of stroke and improving the post-stroke-associated functional declines in patients who ate foods rich in micronutrients, including B vitamins and antioxidant vitamins E and C. Folic acid, vitamin B6 and vitamin B12 are all cofactors in homocysteine metabolism. Growing interest has been paid to hyperhomocysteinaemia as a risk factor for CVD. Hyperhomocysteinaemia has been linked to inadequate intake of vitamins, particularly to B-group vitamins and therefore may be amenable to nutritional intervention. Hence, poor dietary intake of folate, vitamin B6 and vitamin B12 are associated with increased risk of stroke. Elevated consumption of fruits and vegetables appears to protect against stroke. Antioxidant nutrients have important roles in cell function and have been implicated in processes associated with ageing, including vascular, inflammatory and neurological damage. Plasma vitamin E and C concentrations may serve as a biological marker of lifestyle or other factors associated with reduced stroke risk and may be useful in identifying those at high risk of stroke. After reviewing the observational and intervention studies, there is an incomplete understanding of mechanisms and some conflicting findings; therefore the available evidence is insufficient to recommend the routine use of B vitamins, vitamin E and vitamin C for the prevention of stroke. A better understanding of mechanisms, along with well-designed controlled clinical trials will allow further progress in this area.

Intake of Mediterranean vegetable soup treated by pulsed electric fields affects plasma vitamin C and antioxidant biomarkers in humans.

The bioavailability of vitamin C from pulsed electric fields (PEF)-treated vegetable soup in comparison with freshly made (FM) vegetable soup—gazpacho—and its impact on 8-epiPGF2α and uric acid concentrations in a human population were assessed. For this purpose six subjects consumed 500 ml PEF-treated vegetable soup/day, and six subjects consumed 500 ml FM vegetable soup/day for 14 days. On the first day of the study, the subjects drank the vegetable soup in one dose (dose–response study), and on days 2–14 they consumed 250 ml in the morning and 250 ml in the afternoon (multiple-dose–response study). Blood was collected every hour for 6 h on the first day and again on days 7 and 14. All blood samples were analyzed for vitamin C, 8-epiPGF2α, and uric acid. The maximum increase in plasma vitamin C occurred 3 h post-dose in both the PEF and the FM groups. Vitamin C remained significantly higher (P≤0.05) on days 7 and 14. The plasma 8-epiPGF2α concentration was significantly lower at the end of the study in both the PEF group (P=0.002) and the FM group (P=0.05). Plasma levels of vitamin C and 8-epiPGF2α were inversely correlated in both groups (r= − 0.549, P=0.018; and r= − 0.743, P=0.0004, respectively). To summarize, drinking two servings (500 ml) of PEF-treated or FM gazpacho daily increases plasma vitamin C and significantly decreases 8-epiPGF2α concentrations in healthy humans.