Diphenyl-1-picrylhydrazyl Method Research Articles

A Study on Antioxidant Property of Organic and Conventional Tomatoes

Tomato is one of the commonly consumed vegetables with high antioxidant capacity. The objective of the present study is to compare the antioxidant property of organic and conventional tomatoes. For the experiment, organic samples were procured from Era Organic Foods, (IMO Certified) Bangalore. Same variety of conventional tomato was obtained from same agro climatic zone. The samples were freeze dried using a lyodryer (LT5BC ISI lyphilization system, USA) and stored at 4 C in dark. The tomato extract was prepared in a solvent consisting of methanol (69%), ethanol (20%), HCl (10%) and water (1%). Total antioxidant capacity was estimated using Free Radical scavenging activity using 2, 2 Diphenyl-1-picryl hydrazyl (DPPH),β Carotene bleaching method, Linoleic acid emulsion system-thiocyanate method and Ferric-reducing antioxidant power(FRAP) methods. The results reveal that organic tomatoes have higher antioxidant ability than conventional tomatoes. These differences are significantly higher in case of DPPH method, β Carotene bleaching method but not significant in case of Linoleic acid emulsion system-thiocyanate method and Ferric- reducing antioxidant power method.

Comparison of a silver nanoparticle-based method and the modified spectrophotometric methods for assessing antioxidant capacity of rapeseed varieties

The antioxidant capacity of 15 rapeseed varieties was determined by the proposed silver nanoparticle-based (AgNP) method and three modified assays: ferric reducing antioxidant power (FRAP), 2,2′-diphenyl-1-picrylhydrazyl (DPPH) and Folin–Ciocalteu reducing capacity (FC). The average antioxidant capacities of the studied rapeseed cultivars ranged between 5261–9462, 3708–7112, 18864–31245 and 5816–9937μmol sinapic acid (SA)/100g for AgNP, FRAP, DPPH and FC methods, respectively. There are significant, positive correlations between antioxidant capacities of the studied rapeseed cultivars determined by four analytical methods (r=0.5971–0.9149, p<0.05). The comparable precision for the proposed AgNP method (RSD=1.4–4.4%) and the modified FRAP, DPPH and FC methods (RSD=1.0–4.4%, 0.7–2.1% and 0.8–3.6%, respectively), demonstrate the benefit of the AgNP method in the routine analysis of antioxidant capacity of rapeseed cultivars. The principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used for discrimination the quality of the studied rapeseed varieties based on their antioxidant potential determined by different analytical methods. Three main groups were identified by HCA, while the classification and characterisation of rapeseed varieties within each of these groups were obtained from PCA. The chemometric analyses demonstrated that, rapeseed variety S13 had the highest antioxidant capacity, thus this cultivar should be considered as the richest source of natural antioxidants.

Myrtus communis L. Infusions: The Effect of Infusion Time on Phytochemical Composition, Antioxidant, and Antimicrobial Activities

In traditional medicine, myrtle (Myrtus communis L.) is frequently consumed as an infusion and decoction. In this study, we investigate the phenolic and volatile compositions and antioxidant and antibacterial activities of leaf infusions prepared during 3 different times. The total phenolics contents (146.74 to 179.55 mg GAE/g DM) varied significantly between infusions. Eleven phenolic compounds were identified by reversed-phase high-performance liquid chromatography. Phenolic acids (7.64 to 14.28 μmol/g DM) and flavonol glycosides (7.05 to 12.11 μmol/g DM) were the major phenolic fractions of infusions. Significant quantitative variation in 6 phenolic components was observed between infusions. Sixteen volatile components were identified by gas chromatography (GC) and GC mass spectrometry analyses. The main constituents were 1,8-cineole (42.58% to 51.39%), α-terpineol (9.45% to 9.72%), methyl eugenol (6.69% to 7.11%), and linalool (5.91% to 6.06%). Quantitative variations of the volatile components of the analyzed oils in relation to the infusion time were observed. The antioxidant properties of infusions, assayed through DPPH (2,2- diphenyl-1-picrylhydrazyl) method, β-carotene bleaching test, chelating effect on ferrous ions, and ferric reducing power method, were considerable and varied according to the infusion time. Myrtle infusions exhibited a substantial antimicrobial activity against 6 tested bacteria.

A silver nanoparticle-based method for determination of antioxidant capacity of rapeseed and its products

A novel silver nanoparticle-based (AgNP) method and two modified procedures, ferric reducing antioxidant power (FRAP) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH), were used for determination of antioxidant capacities of the ethanolic, methanolic, methanolic-aqueous (1 : 1 v/v) and aqueous extracts of rapeseed and its products. The AgNP method based on the electron-transfer reaction between silver ions and antioxidants in an optimized ammonium buffer medium (pH = 8.4) and determination of silver nanoparticle formation has been elaborated. The novel AgNP method was validated using sinapic acid, gallic acid, caffeic acid, ascorbic acid and quercetin as standard antioxidant solutions in concentration ranges of 0.03-0.21 µmol mL(-1), 0.02-0.20 µmol mL(-1), 0.01-0.18 µmol mL(-1), 0.03-0.30 µmol mL(-1) and 0.001-0.009 µmol mL(-1). The calculated detection (DL = 0.01, 0.02, 0.009, 0.02 and 0.0004 µmol mL(-1) for sinapic, gallic, caffeic, ascorbic acids and quercetin, respectively) and quantification limits (QL = 0.04, 0.06, 0.03, 0.08 and 0.001 µmol mL(-1) for sinapic, gallic, caffeic, ascorbic acids and quercetin, respectively) confirm linearity concentration ranges for determination of antioxidant capacity by AgNP assay. The average antioxidant capacities of the studied rapeseed samples ranged between 14.7 and 126.2 µmol sinapic acid per gram for the proposed AgNP method, 7.4-112.7 µmol sinapic acid per gram for the FRAP method and 39.1-339.8 µmol sinapic acid per gram for DPPH assay. The methanol-water mixture (1:1 v/v) was the most efficient solvent for extraction of antioxidants from the studied rapeseed samples. There are significant, positive correlations between the novel AgNP and the modified FRAP, DPPH and FC methods for all extracts of the studied rapeseed samples (r = 0.7564-0.8516, p < 0.001). Satisfactory values of precision (RSD = 1.2-4.4%) and accuracy (recovery = 95.6-104.6%, except methanolic extracts) demonstrate the benefit of the proposed AgNP method for analysis of the antioxidant capacity of rapeseed samples. Results of the principal component analysis (PCA) indicate that there are differences between the total amounts of antioxidants in rapeseed samples extracted by different solvents.

Phenolic compounds and antioxidant activity of olive leaf extracts

The total phenolic content and antioxidant activities of olive leaf extracts were determined. Plant material was extracted with methanol and fractionated with solvents of increasing polarity, giving certain extracts. The qualitative changes in the composition of the extracts were determined after the storage of leaves for 22 h at 37°C, before the extraction. Total polyphenol contents in extracts were determined by the Folin–Ciocalteu procedure. They were also analysed by liquid chromatography–mass spectrometry. Their antioxidant activities were evaluated using the diphenyl picrylhydrazyl method and the β-carotene linoleate model assay. Moreover, the effects of different crude olive leaf extracts on the oxidative stability of sunflower oil at 40°C and sunflower oil-in-water emulsions (10% o/w) at 37°C, at a final concentration of crude extract 200 mg kg−1 oil, were tested and compared with butylated hydroxyl toluene.

On practical problems in estimation of antioxidant activity of compounds by DPPH [rad] method (Problems in estimation of antioxidant activity)

2,2′-Diphenyl-1-picrylhydrazyl (DPPH ) method is commonly applied for the estimation of antioxidant activity of single compounds and their mixtures. The method is based on the spectrophotometric measurement of DPPH concentration changes resulting from the DPPH reaction with an antioxidant. The amount of remaining DPPH in the examined system is a measure of the antioxidative activity of compounds. The study shows that the type and amount of solvent used for the antioxidant dissolution, water content, and hydrogen or metal ion concentration in the measuring system significantly influence the differences in the amount of unreacted DPPH . The presence of ethyl acetate or dioxane or metal ions in the system decreases the kinetics of the reaction between DPPH and butylohydroxytoluene in relation to its kinetics in the system containing only methanolic solutions. The opposite effect is observed for water, low concentration of chloroform or hydrogen ions. The presented relationships confirm the necessity of standardising the DPPH method and show the complexity of the problem, even in very simple DPPH /antioxidant systems.

Evaluation of Clausena anisata Essential Oil from Cameroon for Controlling Food Spoilage Fungi and its Potential Use as an Antiradical Agent

Investigations were conducted to determine the chemical composition, antifungal and antiradical activities of the essential oil extracted from the fresh leaves of Clausena anisata (Willd.) Hook. F. ex Benth (from Cameroon) against Aspergillus flavus, A. niger, A. parasiticus and Fusarium moniliforme. The essential oil obtained by hydrodistillation was analysed by GC and GC/MS. The disc diffusion method was used to evaluate the fungal growth inhibition at various concentrations of the oil while the antiradical activity of the essential oil was studied by the DPPH (diphenyl picryl hydrazyl) method. The main components obtained were E-ocimenone (15.1%), Z-ocimenone (11.5%), gamma-terpinene (11.4%) and germacrene D (10.9%). After 10 days of incubation on essential oil supplemented medium, the growth of A. flavus, A. niger, A. parasiticus and F. moniliforme were totally inhibited by 4, 5, 5 and 5 mg/mL of C. anisata essential oil, respectively. The antiradical activity of C. anisata essential oil (SC50 = 5.1 g/L) was less than that of butylated hydroxyl toluene (BHT), which was used as the reference compound (SC50 = 0.007 g/L). Results obtained in the present study indicate the possibility of exploiting C. anisata essential oil to fight strains of A. flavus, A. niger, A. parasiticus and F. moniliforme responsible for biodeterioration of stored food products.

Antioxidant capacity, total phenolics, glucosinolates and colour parameters of rapeseed cultivars

The antioxidant capacity of twenty nine rapeseed varieties was determined by using ferric reducing antioxidant power (FRAP) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) methods. Mean FRAP (3190–6326μmol Trolox/100g) and DPPH (3194–6346μmol Trolox/100g) values for methanolic extracts of rapeseed cultivars did not differ significantly. Moreover, the total content of phenolics (756–1324mg sinapic acid/100g), glucosinolates (4.2–87.5μmol/g, respectively), erucic acid (0.0–56.1%) and colour parameters of the studied rapeseed cultivars were analysed. Antioxidant capacity determined by FRAP and DPPH methods correlated significantly with total phenolic content (TPC) in rapeseed cultivars (r=0.9332, 0.9339, p<0.001). Also, significant, inverse correlations were found between antioxidant capacity, total phenolics and luminosity (L∗) or red colour intensity (a∗) of rapeseed cultivars. Principal component analysis (PCA) allowed the rapeseed varieties to be differentiated based on their antioxidant capacities, total amounts of phenolics, glucosinolates, erucic acid and colour parameters.

Free radical scavenging abilities of flavonyl‐thiazolidine‐2,4‐dione compounds

Free radical scavenging activity of flavonyl-thiazolidine-2,4-dione compounds has been evaluated using chemiluminescence, electron spin resonance spectroscopy with 5,5-dimethyl-1-pyrroline-1-oxide as spin trap and DPPH (2,2'-diphenyl-1-picrylhydrazyl) method. The examined compounds exhibited 28-50% scavenging superoxide anion radical O₂⁻ⁱ16.7-76.7% hydroxyl radical (HO•) and 9-40% DPPH radical. Compounds containing carbonyl group in their structure can be considered as antioxidants with high relevance and great biological importance.

Potential antioxidant and anti-inflammatory properties in Teucrium salviastrum Schreb.

Teucrium salviastrum Schreb. (Lamiaceae) is an endemic species from central and northern highlands of Portugal occurring usually in areas above 1.000m [1]. Teucrium spp. have been widely used as medicinal herbs and the biological activities of some species were already studied [2,3]. Here, for the first time, the phenolic composition of T. salviastrum extracts was determined, and their antioxidant and anti-inflammatory activities were assessed in vitro. Aerial parts of the plant were pulverized and extracted successively with dichloromethane, ethanol and 50% aqueous ethanol. Total phenols were determined by the Folin-Ciocalteu colorimetric method. Extracts were screened for their antioxidant activity using the 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging method. The anti-inflammatory activity was assessed by the Griess method, evaluating the nitric oxide (NO) production, in the macrophage cell line Raw264.7 stimulated with lipopolysaccharide (LPS). HPLC-PDA-ESI/tandem MS was performed to obtain the phenolic profiles of the extracts. The DPPH method revealed that the ethanolic and hydro-alcoholic extracts are good free radical-scavengers. Additionally, these extracts inhibited LPS-induced macrophage NO production, a well known marker of the inflammatory processes. Relevant results were obtained for the ethanolic and hydro-alcoholic extracts, which showed, respectively, 0.175 and 0.095g of total phenols expressed in gallic acid equivalent/1g dry extract, which were, for most part, constituted by phenolic acid derivatives and a luteolin derivative. These results suggest that both ethanolic and hydro-alcoholic extracts of T. salviastrum have antioxidant and anti-inflammatory activities which could be related to the phenolic compounds and that the species has potential medicinal properties.

COMPARISON OF CHEMICAL COMPOSITION AND ANTIOXIDANT ACTIVITY OF GLYCOSIDICALLY BOUND AND FREE VOLATILES FROM CLOVE (EUGENIA CARYOPHYLLATATHUNB.)

The present article reports on the chemical composition and antioxidant activity of clove glycosidically bound volatile compounds in comparison with their essential oil. The comparison of chemical composition of volatile aglycones with the chemical composition of essential oil revealed only eugenol as identical. To measure the antioxidative activity of the clove enzymatically released aglycones and its essential oil, two different assays were performed: the 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging method and the ferric reducing/antioxidant power (FRAP) assay. Both methods showed that the clove volatile aglycones possess lower antioxidant properties than its essential oil. The volatile aglycones radical-scavenging activity measured by DPPH method was lower than butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) activity. The reducing capacity measured by FRAP method for volatile aglycones was lower than BHA capacity and higher than BHT capacity. Some differences in activity obtained by two methods could be explained with different solvent polarity. PRACTICAL APPLICATIONS Many secondary metabolites are glycosylated and accumulate as nonvolatile glycosides. Since the glycosides are able to release their aglycones by enzymatic hydrolysis, these compounds could be considered as possible precursors of antioxidant substances in plant. They may contribute to the total antioxidant activity of plant and could be used as natural antioxidants.

Composition and Antioxidant Activity of Olive Leaf Extracts from Greek Olive Cultivars

AbstractThe olive leaf phenolic composition of the Greek cultivars koroneiki, megaritiki and kalamon was determined using LC/MS. Furthermore, the antioxidant activity of olive leaf extracts from the above three cultivars, using solvents of increasing polarity (petroleum ether, dichloromethane, methanol and methanol/water: 60/40) was evaluated using the stable free radical diphenylpicrylhydrazyl (DPPH) test. Furthermore the oxidative stability index (OSI) was compared to that of the synthetic antioxidant TBHQ and commercial oleoresin (rosemary extract). The ability of phenolic compounds to inhibit the lipoxygenase (LOX) activity was also investigated. The ten main components determined in the olive tree leaf extracts for the cultivars koroneiki and kalamon were: secologanoside, dimethyloleuropein, oleuropein diglucoside, luteolin‐7‐O‐glucoside, rutin, oleuropein, oleuroside, quercetin, ligstroside and verbascoside. Respective compounds for the cultivar megaritiki were: secologanoside, dimethyloleuropein, oleuropein diglucoside, luteolin7‐O‐glucoside, oleuropein, oleuroside, quercetin and ligstroside. In all three cultivars, oleuropein represented the main phenolic component. The solvent polarity influenced the total amount of the phenolic compounds determined. When methanol/water (60/40) was used, as solvent, more phenolic compounds were determined. The total amounts of phenols determined in the extracts, obtained by successive extractions using the above solvents, were 6,094, 5,579 and 6,196 mg/kg (mg gallic acid/kg dried olive leaves) for the cultivars megaritiki, kalamon and koroneiki, respectively. Among all extracts, methanol/water extracts exhibited the highest antioxidant activity as shown through the application of the DPPH and OSI methods. The OSI antioxidant activity followed the sequence: synthetic antioxidant TBHQ &gt; commercial oleoresin &gt; olive tree leaf extracts &gt; control. Likewise, methanol/water olive leaf extracts significantly inhibited soybean lipoxygenase, although some small differences in the activity among the olive leaf extracts of the different cultivars were observed. The solvent polarity as well as the amount of the extract influenced the inhibitory activity. A positive correlation was shown between the antioxidant activity of leaf extracts and the total phenol content.

The influence of addition of various sweet potatoes (Ipomea batatas) extract to total count of cells and antioxidant activity in yogurt

Retnati, Andriani MAM, Fauza G. 2009. The influence of addition of various sweet potatoes (Ipomea batatas) extract to total count of cells and antioxidant activity in yogurt. Biofarmasi 7: 68-76. The aim of this research was to determine the influence of addition of various sweet potatoes extract to the total count of cells and the antioxidant activity in yogurt. Yogurt was made from fresh milk, skim milk, white sweet potato, orange sweet potato, purple sweet potato, and pure culture of Streptococcus thermophilus 0040 and Lactobacillus bulgaricus 0041 in straight MRS agar. Fresh milk, skim milk powder (5%, b/v), and sweet potato extract (10%, v/v) was pasteurized at 90oC for 15 minutes, cooled to the temperature between 40-45oC, inoculated with 2.5% S. thermophilus and L. bulgaricus with a proportion of 1.4:1, and then incubated at a temperature of 40oC for 15 hours. Yogurt without an addition of sweet potato extract was used as control. The parameters measured in this experiment were the total count of cells with TPC (Total Plate Count) method and the antioxidant activity with DPPH (2,2- diphenyl-1-picrylhydrazyl) method. Samples were taken at one hour interval to examine the total count of cells, while the antioxidant activity was collected at three hours interval. The result of each analysis was plotted into graphics which describing the relation of total bacteria and antioxidant activity with fermentation time. ANOVA was employed to analyze the data. If there was a significant difference, it should be followed by Duncan Multiple Range Test (DMRT) at a significance level α=0.05. The result of this research showed that the addition of various sweet potatoes extracts increased the total count of cells and the antioxidant activity in yogurt. The total count of cells showed no significant different for each sample, it meant that the different colors in sweet potato did not influence the total count of cells. However, yogurt with orange and purple sweet potato extract addition had a significant difference on the antioxidant activity with control and yogurt with white sweet potato extract. In conclusion, the difference colors in sweet potato influenced in the antioxidant activity in yogurt significantly. Sweet potato is potential for milk substitute in yogurt production due to oligosaccharide content and antioxidant activity.

Antiradical potential and antifungal activities of essential oils of the leaves of Citrus latifolia against Phaeoramularia angolensis

Investigations were conducted to determine the chemical composition, antiradical and antifungal activities of the essential oil extracted from the fresh leaves of Citrus latifolia var. Tahiti from Cameroon against Phaeoramularia angolensis. The essential oil obtained by hydrodistillation was analysed by GC and GC/MS. The disc diffusion method was used to evaluate the zone of fungal growth inhibition at various concentrations of the oil while the antiradical activity of the oil was studied by the DPPH (diphenyl picryl hydrazyl) method. The chemical analysis revealed 26 components among which limonene (45.76%), geranial (13.12%) and neral (10.35%) were the main components. The antiradical activity of C. latifolia essential oil (SC50 = 9.93 g/l) was less than that of butylated hydroxyl toluene (BHT) which was used as the reference compound (SC50 = 7.02 x 10-3 g/l). After 40 days of incubation on oil – supplemented medium, the growth of P. angolensis was totally inhibited by 1600 mg/l of C. latifolia oil. Results obtained in the present study indicate the possibility of exploiting C. latifolia var Tahiti essential oil to combat P. angolensis which is responsible for heavy losses of Citrus fruits harvests.

Free radical scavenging activity of aqueous extract of roots of Baliospermum montanum Muell-Arg

Free radical scavenging potential of the aqueous extract of roots of Baliospermum montanum Muell-Arg, a medicinal plant, was evaluated by using diphenyl-picryl-hydrazyl (DPPH) assay and nitric oxide (NO) scavenging assay. Th e in vitro antioxidant activity of the plant extract was determined by DPPH and NO scavenging activity method. In the DPPH method, antioxidants present in the plant extract reacted with DPPH, which is a stable free radical, and converted it to 1,1-diphenyl-1,2-picryl, hydrazine. Th e results were expressed as IC50. Ascorbic acid, which was used as a standard, showed an IC50 of 19.90 ± 2.3 μg/ml, whereas the plant extract showed an IC50 of 26.22 ± 0.8 mg/ml. In the second method, NO generated from sodium nitroprusside in aqueous solution at physiological pH interacted with oxygen to produce nitrite ion, which was measured at 540 nm. Ascorbic acid, the standard, showed an IC50 of 5.62 ± 2.5 μg/ml; the plant extract showed an IC50 of 36.66 ± 2.8 μg/ml. In the present study, aqueous extract of B. montanum showed remarkable and concentration-dependent free radical scavenging activity comparable to that of a standard such as ascorbic acid in the studied models; signifi cant results were observed in the estimated parameters, thereby indicating that B. montanum has promising free radical scavenging activity. Key words: Baliospermum montanum, DPPH assay, free radical scavenging, nitric oxide assay

Chemical Composition, Antiradical and Antifungal Activities of Essential Oil of the Leaves of Cinnamomum Zeylanicum Blume from Cameroon

The aim of the present study was to investigate the essential oil of Cinnamomum zeylanicum from Cameroon for its chemical composition, antiradical and antifungal activities against some common fungi causing spoilage of stored food product. The essential oil, obtained by hydrodistillation of fresh leaves, was analysed by GC and GC/MS. The oil contains 11 components among which eugenol (89.1%), linalool (4.3%), benzoate benzyl (3.1%) and cinnamaldehyde (1.5%) were the main components. Determination of antiradical activity of the oil was studied by the DPPH (diphenyl picryl hydrazyl) method. The antiradical activity of Cinnamomum essential oil (SC50 = 4.5 mg/L) was higher than that of butylated hydroxy toluene (BHT), which was used as the reference compound (SC50 = 7 mg/L). The growth inhibitory effect of C. zeylanicumn essential oil on Aspergillus flavus and Fusarium moniliforme was determined on potato dextrose agar. After 9 days of incubation on essential oil-supplemented medium, the growth of A. flavus and Fusarium was totally inhibited by 500 ppm of Cinnamommum zeylanicum oil. Results obtained in the present study indicate the possibility of exploiting C. zeylanicum essential oil to prevent diseases such as diabetes and cancer, to slow down ageing, and also to combat strains of A. flavus and Fusarium moniliforme responsible for biodeterioration of stored food products.

Capabilities of Oat Extracts in Inhibiting Cholesterol and Long Chain Fatty Acid Oxidation During Heating

ABSTRACTThe antioxidant activities of oat groat extracts using different solvents were investigated. For acetone, hexane, and methanol extracts, the total phenolic compound contents were 12.83, 8.56, and 26.17 μg of catechin equivalent/g, respectively. Their corresponding free radical scavenging activities measured using the DPPH (2,2'‐diphenyl‐1‐picrylhydrazyl) method were 0.68, 0.35, and 0.79 μmol of Trolox equivalent/g, respectively. All oat extracts presented significantly greater capability in preventing cholesterol oxidation than the control (no extract added) during heating at the three levels of addition (1, 5, and 10 mg). The capability of the hexane or acetone extract in preventing cholesterol oxidation was not as effective as the methanol extract. In the docosahexaenoic acid (DHA, C22:6) oxidation test, all oat extracts at the level of 5 and 10 mg had greater inhibition capability on DHA oxidation than the control (DHA only). No significant inhibition was found for the hexane and acetone extract at the level of 1 mg, except for the methanol extract. The capabilities of oat extracts to inhibit oxidation of cholesterol and DHA from high to low was methanol, acetone, and hexane extract, which agreed with their free radical scavenging activities and total phenolic compound contents.

Antioxidants from a heated histidine‐glucose model system. Investigation of the copper(II) binding ability

AbstractThe metal binding ability of Maillard reaction products (MRP) was investigated by spectrophotometric monitoring for complex/chelate formation. In addition, the antioxidant activity of MRP, in the presence of Cu(II), was evaluated on a lipid model system consisting of sunflower seed oil/water (1∶2). Results from the Rancimat test indicated a significant decrease in pro‐oxidant ability of Cu(II) in the presence of MRP in contrast to histidine alone, whether heated or not. Results from the diphenylpicrylhydrazyl method showed that, in contrast to histidine (heated or not), the antiradical ability of MRP is reduced in the presence of Cu(II), but depends on the reaction time between MRP and Cu(II).