Antiradical Efficiency Research Articles

The efficiency of flavonoids in polar extracts of Lycium chinense Mill fruits as free radical scavenger

The extracts of Lycium chinense Mill fruits with water, 50% ethanol and 95% ethanol were compared in antiradical efficiency according to the Chinese consumption tradition. The results showed that water infusion was similar to 50% ethanol extract in flavonoids (1154 ± 89 and 1207 ± 66 mg kg −1, respectively), 95% ethanol extract contained more flavonoids (1497 ± 70 mg kg −1). The main flavonoids in Lycium chinense Mill fruits were rutin and chlorogenic acid in water extract, rutin and protocatechuic acid in 50% ethanol extract and rutin in 95% ethanol extract as determined with high-performance liquid chromatography (HPLC). All extracts showed a slow kinetics in DPPH antiradical reaction system. The antiradical efficiency of the extracts tended to become stronger as the polarity of the solvents decreased.

Antioxidant effects of protein hydrolysates in the reaction with glucose

AbstractMaillard reaction products (MRP) obtained by reaction between glucose and protein hydrolysates from casein and fish were investigated. The influence of parameters such as reaction time and glucose concentration was studied. The antioxidative activity of MRP was determined by using the β‐carotene/linoleate model and the 1,1‐diphenyl‐2‐pricrylhydrazyl method. All experiments showed that the antioxidative effect was improved by 20–30% when the hydrolysates were reached with glucose. A dramatic increase in antiradical efficiency of the MRP (up to 75%) was also observed. The study of the chromatographic profiles obtained before and after the Maillard reaction found changes in absorbance at 280 nm, indicating molecular rearrangements that could be involved in the improvement of the antioxidative and free radical‐scavenging activities.

Enzymic production of a feruloylated oligosaccharide with antioxidant activity from wheat flour arabinoxylan.

Main cereals such as rice, wheat, barley, and corn belong to the family Gramineae and have similar cell-wall composition. Since cereal cell walls are a good source of dietary fibre, meeting one-half of the daily requirement of 30 g of dietary fibre can be achieved by the regular consumption of cereals. Many studies have dealt with the isolation of feruloylated oligosaccharides from Gramineae by treatment with polysaccharide hydrolysing enzymes. Therefore, the purpose of this study was to investigate the production of feruloylated oligosaccharides from insoluble wheat flour arabinoxylan (WFAX) by treatment with a Thermoascus aurantiacus family 10 endoxylanase (XYLI) and the evaluation of their antioxidant activity. The main feruloylated oligosaccharide was purified by anion-exchange and size-exclusion chromatography (SEC). Alkaline saponification and acid hydrolysis were used for product identification. Evaluation of antioxidant activity was performed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) reduction assay and the inhibition of copper-mediated oxidation of low density lipoprotein (LDL). The optimal conditions for WFAX hydrolysis using the XYLI have been determined to be 100 U g(-1) of WFAX for 30 min at 50 degrees C. Saponification of the oligosaccharide released FA and oligosaccharide. The released oligosaccharide consisted of arabinose and xylose in a molar ratio of 1:3 and these results support the identity of the feruloylated oligosaccharide as feruloyl arabinoxylotrisaccharide (FAX(3)). FAX(3) showed profound antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH) reduction assay exhibiting an antiradical efficiency of 0.035 (x 10(-3)) and inhibited the copper-mediated oxidation of human low density lipoprotein (LDL) in a dose-dependent manner with almost complete inhibition at 32 microM. A feruloylated oligosaccharide (FAX3) was isolated from WFAX after enzymatic treatment with XYLI. We verified antioxidant activity of FAX(3) which may be important in preventing or reducing the progression of atherosclerosis by inhibiting the peroxidation of lipoproteins.

Evaluation of the antiradical and reducing properties of selected Greek white wines: correlation with polyphenolic composition

AbstractThe total hydroxycinnamate (THC) and total flavanol (TF) contents were determined in 26 selected Greek white wines of ‘Appellation of Origin of High Quality’ using well‐established spectrophotometric methodology. Furthermore, two parameters related to the antioxidant capacity of wines, the antiradical activity (AAR) and the reducing power (PR), were also determined using the stable DPPH· radical and a ferric reducing power assay respectively. THC content varied from 64.4 to 197.1 mg l−1 chlorogenic acid equivalents (CGAE), whereas TF content exhibited larger variation, ranging from 3.3 to 205.3 mg l−1 catechin equivalents (CTE). AAR and PR were found to range from 0.47 to 0.60 mM Trolox equivalents (TRE) and from 0.32 to 2.05 mM quercetin equivalents (QE) respectively. Regression analysis at 95% significance level indicated that reducing effects are likely to be exerted by the flavanol fraction (SF < 0.05), as opposed to antiradical efficiency which is primarily affected by the sum of THC and TF contents (SF < 0.05), suggesting that synergistic phenomena account for the overall antioxidant status of white wines.© 2002 Society of Chemical Industry

Antiradical efficiency of Maillard reaction mixtures in a hydrophilic media.

The Maillard reaction (MR) has a clear impact in food science, nutrition, and medical research. Free radical scavenging capacities of several MR mixtures made from single combinations of glucose or lactose and amino acids (gly, his, lys, trp, met, and cys) were evaluated by using the N,N-dimethyl-p-phenylenediamine radical cation assay. Medium-roasted coffee brew was used as reference of a thermally processed food. A novel approach has been applied in order to get more information about the kinetic behavior of the radical scavenging properties of MR mixtures in a watery environment. Antiradical efficiency (AE) concept has been applied, and it takes into consideration the reaction time, apart from the amount of antioxidant necessary to decrease by 50% the radical initial concentration (EC(50)). Cysteine and histidine reveal as powerful amino acids to exert a high AE in the MR mixtures. No relationship between AE parameter and browning was observed.

ANTIRADICAL EFFICIENCY OF TEA COMPONENTS

ABSTRACTTea contains antioxidant compounds, such as (‐)‐epicatechin (EC), (‐)‐epigallocatechin (EGC), (‐)‐epicatechin gallate (ECG), (‐)‐epigallocatechin gallate (EGCG), gallic acid and caffeine. The antioxidant activity of these compounds as well as 1,3,7‐trimethyluric acid (the major metabolite of caffeine) was evaluated using the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH). The antiradical ability according to the EC50 was EGCG > ECG > EGC > gallic acid > EC > BHT > 1,3,7‐trimethyluric acid > caffeine. The time for these compounds to reach the steady state was considered, and the concept of antioxidant efficiency (AE50) involving the EC50 and the time to reach the steady state was used to evaluate the antiradical efficacy. The order of antiradical efficiency according to AE50 was ECG gallic acid > EGCG > EC > EGC > BHT > 1,3,7‐trimethyluric acid > caffeine.

Ellagic acid, vitamin C, and total phenolic contents and radical scavenging capacity affected by freezing and frozen storage in raspberry fruit.

The ellagic acid, total phenolic, and vitamin C contents in four raspberry cultivars (Heritage, Autumn Bliss, Rubi, and Zeva) grown in Spain were detected and quantified by HPLC in fresh, just frozen, and stored fruits at -20 degrees C for a one year period. Ellagic acid [207-244 mg kg(-)(1) of fresh weight (fw)], total phenolic (137-1776 mg kg(-)(1) of fw), and vitamin C (221-312 mg kg(-)(1) of fw) contents in raw material were higher in the late cultivars Zeva and Rubi than in the early cultivars Autumn Bliss and Heritage. The freezing process slightly affected the values of extracted ellagic acid, total phenolic, and vitamin C content. At the end of long-term frozen storage (12 months), no significant change of total phenolic content extracted was observed, but significant decreases of 14-21% in ellagic acid and of 33-55% in vitamin C were quantified. Free radical scavenging capacity measured as antiradical efficiency (AE) depends on the seasonal period of harvest. Late cultivars, Rubi (6.1 x 10(-)(4)) and Zeva (10.17 x 10(-)(4)), showed higher AE than early cultivars, Heritage (4.02 x 10(-)(4)) and Autumn Bliss (4.36 x 10(-)(4)). The freezing process produced a decrease of AE values in the four cultivars ranging between 4 and 26%. During the frozen storage, the AE values reached after the freezing process remained unchanged.

Antiradical properties of commercial cognacs assessed by the DPPH(.) test.

Antiradical activities of some commercial cognacs were evaluated by the DPPH(*) test. Different mathematical models for the evaluation of the antiradical efficiency of the cognac samples were proposed and discussed. Nonflavonoid phenols were found to be the main substances responsible of the radical scavenging activity of cognacs. In particular the strongest correlations between antiradical activity measurements and cognac chemical characteristics was found for ellagitannins, high molecular weight polyphenols, which are extracted from the wood and solubilized in the spirit mainly during first year aging.

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

Effect of high-pressure treatment on the carotenoid composition and the radical scavenging activity of persimmon fruit purees.

The carotenoid composition of persimmon fruit purees of two cultivars, cvs. Rojo Brillante and Sharon, grown in Spain was determined by HPLC to assess the effects of high-pressure processing on some sensory (carotenoids), nutritional (provitamin A value), and health-related (radical-scavenging capacity) parameters. Total carotenoid content was higher in untreated Rojo Brillante puree (22. 11 microg g(-)(1)) than in untreated Sharon puree (15.22 microg g(-)(1)). Purees of both untreated cultivars showed similar carotenoid patterns after saponification with beta-cryptoxanthin, beta-carotene, and zeaxanthin as the main pigments. A high content of lycopene was quantified in Rojo Brillante (5.34 microg g(-)(1)), whereas only traces were detected in Sharon. The provitamin A value, reported as retinol equivalents (RE), was in untreated Rojo Brillante puree (77 RE/100 g) similar to that of Sharon (75 RE/100 g). Scavenging free radical capacity, measured as antiradical efficiency (AE), showed in untreated Rojo Brillante puree a value (12.14 x 10(-)(3)) 8.5 times higher than that in untreated Sharon (1. 42 x 10(-)(3)). Nonuniform behavior of high-pressure treatment was detected. Pressure treatments at 50 and 300 MPa/15 min/25 degrees C for Rojo Brillante and at 50 and 400 MPa/15 min/25 degrees C for Sharon increased the amount of extractable carotenoids (9-27%), which are related with the increase of vitamin A value (75-87 RE/100 g). No correlation with the increase of AE (from 1.42 x 10(-)(3) to 16.73 x 10(-)(3) and 19.58 x 10(-)(3)) after some pressure treatments (150 and 300 MPa/15 min/25 degrees C) was found.

Myricetin, an antioxidant flavonol, is a substrate of polyphenol oxidase

The present study demonstrates the antiradical efficiency of myricetin, a flavonol widely distributed in fruits and vegetables, by testing its ability to react with two different free radicals, ABTS+· and DPPH·. The polyphenolic nature of myricetin led us to consider the possibility of its oxidation by polyphenol oxidase (PPO). The results reported show that myricetin can be oxidised by PPO extracted and partially purified from broad bean seeds. The reaction was followed by recording spectral changes with time, maximal spectral changes being observed at 372 nm. The presence of two isosbestic points (at 274 and 314 nm) suggested that only one absorbing product was formed. The spectral changes were not observed in the absence of PPO. The oxidation rate varied with the pH, reaching its highest value at pH 5.5. The myricetin oxidation rate increased in the presence of SDS, an activing agent of polyphenol oxidase. Maximal activity was obtained at 1.3 mM SDS. The kinetic parameters were also determined: V m = 1.35 µM min−1, K m = 0.3,mM, V m/K m = 4.5 × 10−3 min−1. Flavonol oxidation was inhibited by a selective PPO inhibitor such as cinnamic acid (KI = 1 mM). The results reported show that myricetin oxidation was strictly dependent on the presence of polyphenol oxidase. © 1999 Society of Chemical Industry

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

The free radical scavenging capacity of selected red, rosé 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 rosé 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) > rosé 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

Free radical scavenging capacity of selected red, ros� 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

Free radical scavenging capacity in the aging of selected red Spanish wines.

Free radical scavenging capacity by the DPPH(*) method and main physicochemical properties, polyphenols content by HPLC, color by a tristimulus colorimeter, and UV-vis spectra in the aging of selected red Spanish wines, were studied. As the wines age, they become darker (lower lightness, L) and increase their hue angle (lower red color) as well as the ratio of absorbance at 420 nm to that at 520 nm. Main polyphenolics identified in the samples were tannic acid, oenin, and gallic acid. The antiradical efficiency of the samples increased during aging, which could be related to an increase in the tannic acid concentration shown by the following correlationship: EC(50) = 1/(0.18 + 0.0011[tannic acid](mg/L)) with a correlation coefficient of 0.744.

Oxidation of the flavonol fisetin by polyphenol oxidase

The present study demonstrates the antiradical efficiency of fisetin, a flavonol widely distributed in fruits and vegetables, by its ability to react with two different free radicals, ABTS +⋅ and DPPH ⋅. The polyphenolic nature of fisetin led us to consider whether it might be oxidised by polyphenol oxidase (PPO), and the results reported show that it can be oxidised by PPO extracted and partially purified from broad bean seeds. The reaction was followed by recording spectral changes with time, with maximal spectral changes being observed at 282 nm (increase in absorbance) and at 362 nm (decrease). The presence of two isosbectic points (at 265 and 304 nm) suggested that only one absorbent product was formed. These spectral changes were not observed in the absence of PPO. The oxidation rate varied with the pH, reaching its highest value at pH 5.5. The fisetin oxidation rate increased in the presence of sodium dodecyl sulfate, an activator of polyphenol oxidase. Maximal activity was obtained at 0.87 mM sodium dodecyl sulfate. The following kinetic parameters were determined: V max=49 μM/min, K m=0.6 mM, V max/ K m=8.2×10 −2 min −1. Flavonol oxidation was inhibited by selective PPO inhibitors such as cinnamic acid (a classical competitive inhibitor, K i=1.4 mM) and 4-hexylresorcinol, which behaved as a slow-binding inhibitor. The results reported show that fisetin oxidation was strictly dependent on the presence of polyphenol oxidase.

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 addi-tion 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 [DPPHREM•]=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 (EC50). This parameter, EC50, 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 EC50 (TEC50) was calculated, and antiradical efficiency (AE) was proposed as a new parameter to characterise the antioxidant compounds where AE=1/EC50 TEC50. It was shown that AE is more discriminatory than EC50. AE values are more useful because they also take into account the reaction time. The results have shown that the order of the AE (×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). © 1998 SCI.

A procedure to measure the antiradical efficiency of polyphenols

A procedure to measure the antiradical efficiency of polyphenols

Antiradical activity of 3-hydroxypyridine derivatives

1. The authors have determined the antiradical activity of 3-hydroxypyridine derivatives, and have established the pattern of its variation with their chemical structure. 2. Incorporation of alkyl, hydroxy, methoxy, phenyl, and benzyl groups and condensed benzene rings into the β-pyridol ring, similarly to phenol, increases the antiradical efficiency of 3-hydroxypyridine. 3. The sharpest increase in antiradical activity is observed when hydroxy or methoxy groups are introduced into the hydroxypyridine ring of 2-phenyl-, 2- and 5-henzyl-3-hydroxypyridines.