María D. Rivero-Pérez

Infusions of Portuguese medicinal plants: Dependence of final antioxidant capacity and phenol content on extraction features.

BACKGROUND Aqueous extracts of most medicinal plants traditionally employed in Portugal (at the ratio of 1 g plant: 110 mL water) have been assayed for total antioxidant capacity and phenol content, in order to elucidate their claimed medicinal features. RESULTS The antioxidant activity was assessed by the ABTS(•+) method; the ascorbic acid equivalent values ranged from 1.4280 ± 0.1261 g L(-1) for avocado (Persea americana (Lauraceae)) obtained by infusion of powder, down to 0.0027 ± 0.0012 g L(-1) for olive (Olea europaea (Oleaceae)) obtained by infusion of leaves. Total phenol content was determined by the Folin-Ciocalteu procedure; the gallic acid equivalent values ranged from 0.5541 ± 0.0289 g L(-1) for avocado obtained by infusion of powder, down to 0.0053 ± 0.0014 g L(-1) for olive obtained by boiling leaves. A good correlation between total antioxidant capacity and total phenol content was found. CONCLUSION The method of powder infusion should be chosen if high concentration of antioxidants are sought. On the other hand, a high antioxidant capacity and a high phenol content correlate well with the empirically established (and widely publicised) capacity to treat respiratory infections. Copyright

Influence of the Degree of Roasting on the Antioxidant Capacity and Genoprotective Effect of Instant Coffee: Contribution of the Melanoidin Fraction

The roasting process induces chemical changes in coffee beans that strongly affect the antioxidant activity of coffee. In this study, the polyphenol and melanoidin contents and the antioxidant activity of three instant coffees with different roasting degrees (light, medium, and dark) were assessed. Coffee brews were separated into fractions, and the potential biological activity of the melanoidins was evaluated by simulating their gastrointestinal digestion. Total antioxidant capacity, hydroxyl radical scavenger activity, lipid peroxidation inhibition capacity, and protection against DNA oxidative damage (in vitro and ex vivo genoprotective effects) were determined. We report that instant coffee has a high total antioxidant capacity and protective effect against certain oxidative stress biomarkers (lipids and DNA), although this capacity decreases with the roasting degree. Our study confirms the hypothesis that several of the polyphenols present in coffee may become part of the melanoidins generated during roasting. Furthermore, the elevated genoprotective effect of melanoidin-digested fractions is noteworthy.

Adaptation and Validation of QUick, Easy, New, CHEap, and Reproducible (QUENCHER) Antioxidant Capacity Assays in Model Products Obtained from Residual Wine Pomace.

Evaluation of the total antioxidant capacity of solid matrices without extraction steps is a very interesting alternative for food researchers and also for food industries. These methodologies have been denominated QUENCHER from QUick, Easy, New, CHEap, and Reproducible assays. To demonstrate and highlight the validity of QUENCHER (Q) methods, values of Q-method validation were showed for the first time, and they were tested with products of well-known different chemical properties. Furthermore, new QUENCHER assays to measure scavenging capacity against superoxide, hydroxyl, and lipid peroxyl radicals were developed. Calibration models showed good linearity (R(2) > 0.995), proportionality and precision (CV < 6.5%), and acceptable detection limits (<20.4 nmol Trolox equiv). The presence of ethanol in the reaction medium gave antioxidant capacity values significantly different from those obtained with water. The dilution of samples with powdered cellulose was discouraged because possible interferences with some of the matrices analyzed may take place.

Total antioxidant capacity of new natural powdered seasonings after gastrointestinal and colonic digestion

New powdered seasonings, rich in natural antioxidant compounds, have successfully been applied recently in different food matrices. Once ingested, the antioxidants contained in these seasonings may exert protective effects against oxidative stress along the gastrointestinal tract. This fact was evaluated by submitting the different seasonings under study to simulated digestion followed by assessing the reducing and antiradical capacities of the digested fractions. Enzymatic gastrointestinal digestion enhanced 2-3 times both antioxidant activities and colonic fermentation increased more than 10-fold the radical scavenging ability of digested fractions compared with undigested seasonings. Digested fractions derived from the seedless wine pomace seasoning presented generally the highest antioxidant properties. The results were evaluated considering bioaccessibility factors to have a more realistic overview of the potential antioxidant capacities of the seasonings and of the probable beneficial effects of their consumption on the prevention of oxidative damage along the gut.

The effects of heat treatment on the phenolic composition and antioxidant capacity of red wine pomace seasonings

The impact of thermal processing on the phenolic profile and antioxidant capacity (TAC) of powdered red wine pomace seasonings (RWPSs) obtained from different sources (seedless: Sk-S; whole: W-S; seeds: Sd-S) was assessed. High contents in anthocyanins, flavonol-3-O-glycosides, phenolic acids and flavan-3-ols were found in Sk-S, whereas flavan-3-ols and phenolic acids were the main compounds identified in Sd-S. Reductions in the anthocyanidin and flavonol-3-ol contents mainly determined the effect of heat on the total phenolic contents (Sk-S: -29.4%; W-S: -28.0%; Sd-S: -5.78%), although heating affected positively the phenolic acid and flavonol aglycon contents. Slight TAC decreases were observed in the RWPS-derived extracts (classical Folin-Ciocalteu and ABTS assays). However, higher TAC reductions were detected when the powdered RWPSs were used directly as samples (QUENCHER approach). In conclusion, there is little evidence against submitting RWPSs to thermal processing, as heating affects differently each type of phenolic compound and does not induce very severe TAC decreases in these seasonings.

Chemopreventive Potential of Powdered Red Wine Pomace Seasonings against Colorectal Cancer in HT-29 Cells

This study evaluates the antiproliferative and antigenotoxic actions of powdered red wine pomace seasonings (Sk-S, seedless; W-S, whole; Sd-S, seeds). In vitro gastrointestinal digested and colonic fermented fractions of the seasonings were used as cell treatments. Phenolic acids from Sk-S showed the highest bioaccessibility in the small intestine, whereas polyphenols contained in Sd-S might be the most fermentable in the colon. Dietary fiber from Sk-S was the best substrate for short chain fatty acids production by gut microbiota. Colon cancerous (HT-29) cell viability was inhibited by 50% (IC50 values) at treatment concentrations ranging from 845 (Sk-S) to 1085 (Sd-S) μg/mL prior digestion, but all digested fractions exhibited similar antiproliferative activities (mean IC50 = 814 μg/mL). Oxidative DNA damage in cells was also attenuated by the treatments (200 μg/mL, 24 h preincubation), with all colonic fermented fractions displaying similar genoprotective action. These results suggest the potential of red wine pomace seasonings as chemopreventive agents in colorectal cancer.

Attenuation of oxidative stress in Type 1 diabetic rats supplemented with a seasoning obtained from winemaking by-products and its effect on endothelial function

Type 1 diabetes mellitus (DM) is characterized by hyperglycemia resulting from insulin deficiency. This is usually accompanied by a pro-oxidative environment, dyslipidemia and endothelial dysfunction, thus leading to several micro- and macro-vascular complications. This study investigated the potential benefits of a seasoning obtained from seedless red wine pomace (RWPS) in protecting against oxidative damage and preserving endothelial function in Type 1 DM, and the underlying mechanisms involved at the level of gene expression. The diet of streptozotocin (45 mg kg-1)-induced diabetic (DB) and control (CN) male Wistar rats (n = 5 rats per group) was supplemented with RWPS (300 mg per kg per day) or vehicle for 4 weeks. Characteristic indicators of DM such as increased food and water intakes and weight loss were significantly ameliorated in DB + RWPS rats, with a notable normalization in their fasting glycemic control and cholesterol profile. Plasma total antioxidant capacity (TAC) was substantially increased, and biomarkers of oxidative damage to lipids (F2-isoprostanes, 24.9%; malondialdehyde, 28.4%) and proteins (carbonyl groups, 5.91%) were significantly decreased. Nitric oxide availability tended to improve in plasma of DB + RWPS compared with DB rats. Insulin levels were increased (1.51-fold) and aortic tissue antioxidant enzymes such as mitochondrial superoxide dismutase (SOD2, 1.93-fold) were up-regulated. Other important genes for endothelial function, including endothelial β-nicotinamide adenine dinucleotide phosphate oxidase (NOX4), endothelial and inducible nitric oxide synthases (eNOS, iNOS), and angiotensin-converting enzyme-I (ACE), were non-significantly modulated, although certain potentially positive trends were observed. These results indicate that RWPS supplementation might be a useful nutritional approach to manage Type 1 DM and ameliorate its vascular complications.