Optimization of capillary zone electrophoresis separation and on-line preconcentration of 16 phenolic compounds from wines produced in South America

A capillary zone electrophoresis method was optimized to simultaneously separate 16 phenolic compounds present in wines, as well as to evaluate sample on-line preconcentration for detectability improvement. The separated compounds were narirutin, (?)-epicatechin, (+)-catechin, rutin, kaempferol, myricetin, quercetin, morin, trans-resveratrol, cinnamic acid, ferulic acid, p-coumaric acid, vanillic acid, caffeic acid, gallic acid, and 3,4-dihydroxybenzoic acid. The optimized separation condition was 175 mmol L^? 1 boric acid at pH 9.0 and capillary of 50 μm × 68 cm (60 cm effective length). The injection mode showing the greatest detectability (20 fold improvement) was hydrodynamic injection at 50 mbar for 30 s, followed by voltage inversion (? 20 kV for 5 s) before the electrophoretic run. The method was validated and applied with success in a total of 23 samples of red, white, and rose wines. The developed method showed excellent applicability due to the simple extraction procedure and the low volume of reagents used, reducing expenses for reagents and technicians.     

Phenolic composition,antioxidant and antimicrobial activities of free and bound phenolic extracts of Moringa oleifera seed flour

Phenolic compounds, antioxidant and antibacterial activities of defatted Moringa oleifera seed flour (DMF) were investigated. The total phenolic and flavonoid contents were measured using colorimetric methods. Free phenolic acid and flavonoid profiles were analyzed by high performance liquid chromatography, while antioxidant capacities were evaluated using scavenging assays of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), ferric reducing antioxidant power and total antioxidant capacity. The results showed that extractability of phenolic compounds was significantly higher (p < 0.05) in bound phenolic extract (4173.00 ± 32.22 mg gallic acid equivalents (GAE)/100 g) than in free phenolic extract (780.00 ± 14.2 mg GAE/100 g) and it showed higher antioxidant and antimicrobial activities. The IC₅₀ value for DPPH radical scavenging activity was 0.9 ± 0.05 and 14.9 ± 0.07 mg/mL for bound phenolic and free phenolic extracts, respectively. Bound phenolic extract was more effective (minimum inhibitory concentration (MIC), 0.06–0.157%) than free phenolic extract (MIC, 0.117–0.191%) against tested bacteria. Ten phenolic compounds (gallic acid, p-coumaric acid, ferulic acid, caffeic acid, protocatechuic acid, cinnamic acid, catechin, epicatechin, vanillin and quercetin) were identified and quantified in both extracts. These natural plant phenolics from Moringa seeds could be a good source of antioxidants and antibacterials for food and pharmaceutical industries.     

Determination of phenolic composition and antioxidant capacity of native red wines by high performance liquid chromatography and spectrophotometric methods

A reversed-phase high performance chromatographic method for simultaneous determination of 14 phenolic compounds in native red wines was developed in this study. The identified compounds contained gallic acid, (+)-catechin, 3,4-dihydroxybenzoic acid, chlorogenic acid, (?)-epicatechin, 4-hydroxybenzoic acid, syringic acid, caffeic acid, p-coumaric acid, rutin, resveratrol, myricetin, quercetin and kaempferol. The method includes liquid–liquid extraction of acidic pH with ethylacetate. The analysis used a Zorbax Eclipse XDB-C18 column (5 μm, 4.6 mm × 250 mm). The chromatographic separation of these compounds performed in a single run by using the mobile phase gradient elution of methanol water mixture (% 0.2 formic acid) at room temperature, with flow rate at 1 mL/min. Detection was carried out by UV–vis and fluorescence detector. Each analysis required an equilibration period of 10 min and a run time of 14 min for completion. The optimized chromatographic method was carefully validated for precision and accuracy. Our findings indicated that the developed HPLC method was precise, accurate, specific and sensitive for simultaneous determination of phenolic compounds. Consequently, the described method was applied to the analysis of six wines from Malatya and Elaz??. Gallic acid was dominant phenolic acid in red wines. (+)-catechin, (?)-epicatechin and p-coumaric acid were the next most abundant phenolics. The highest level of trans-resveratrol among the red wines was found Buzba?? (Bogazkere–Öküzgözü). The red wines were analyzed for total polyphenol content (TP) by Folin–Ciocalteu (FC) method, using gallic acid as standard. Antioxidant activities (AA) of the red wines were measured using the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. There was a very high correlation between AA and TP in all of the wines tested.     

Determination of in vitro antioxidant activity of fennel (Foeniculum vulgare) seed extracts

In this study, the antioxidant activity of water and ethanol extracts of fennel (Foeniculum vulgare) seed (FS) was evaluated by various antioxidant assay, including total antioxidant, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, metal chelating activities and reducing power. Those various antioxidant activities were compared to standard antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and α-tocopherol. The water and ethanol extracts of FS seeds showed strong antioxidant activity. 100 μg of water and ethanol extracts exhibited 99.1% and 77.5% inhibition of peroxidation in linoleic acid system, respectively, and greater than the same dose of α-tocopherol (36.1%). The both extracts of FS have effective reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities. This antioxidant property depends on concentration and increasing with increased amount of sample. In addition, total phenolic compounds in the water and ethanol extracts of fennel seeds were determined as gallic acid equivalents. The results obtained in the present study indicated that the fennel (F. vulgare) seed is a potential source of natural antioxidant. Although, the tests presented here show the usefulness of FS extracts as in vitro antioxidants it still needs to be that this extracts show their activity in emulsions, biological systems, health implications or dry foods.     

Analysis of antioxidant activity and antioxidant constituents of Chinese toon

Antioxidant activity of the methanol and water extracts of Chinese toon (Toona sinensis) leaf was evaluated using DPPH radical scavenging and lipid peroxidation assays. Contents of four major types of antioxidants including β-carotene, ascorbate, α-tocopherol and phenolics were also quantified. Open column chromatography followed by semi-preparative HPLC were applied to separate phenolic antioxidants whose contents were subsequently determined by HPLC. The methanol extract demonstrated much higher antioxidant activity than the water extract. Contents of β-carotene, ascorbate, α-tocopherol and phenolics were 1.23 μmol g^?1, 34.2 μmol g^?1, 2.40 μmol g^?1 and 872 μmol gallic acid equivalents g^?1, respectively. Six phenols were isolated. Their structures were characterized as 5-O-galloylquinic acid, gallic acid, methyl gallate, β-1,2,6-tri-O-galloyl-d-glucose, quercetin 3-O-β-d-glucopyranoside and quercetin 3-O-(2′′-O-galloyl)-β-d-glucopyranoside, respectively. The results indicate that phenolic compounds are the dominant antioxidants in Chinese toon. The compounds β-1,2,6-tri-O-galloyl-d-glucose and quercetin 3-O-(2′′-O-galloyl)-β-d-glucopyranoside were reported for the first time in Chinese toon.     

Phenolic compounds and antioxidant activity of Brazil nut (Bertholletia excelsa)

Brazil nuts were shelled and separated as kernel and brown skin; whole nuts were also used. Soluble phenolics from each portion as well as the whole nut were extracted using 70% acetone under reflux conditions. Insoluble-bound phenolics were subsequently extracted into diethyl ether–ethyl acetate mixture (1:1, v/v) after alkaline hydrolysis. Both soluble and insoluble-bound phenolic extracts were separately examined for their total phenolics content; antioxidant activities were evaluated by trolox equivalent antioxidant capacity (TEAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and hydroxyl radical scavenging activities using electron paramagnetic resonance (EPR), reducing power, and oxygen radical scavenging capacity (ORAC). Soluble phenolics in brown skin was 1236.07 as compared to 406.83 in kernel and 519.11 mg/100 g in whole nut. Bound phenolics content of brown skin was also 86- and 19-folds higher than kernel and whole nut, respectively. Similarly extracts from the brown skin exhibited the highest antioxidant activity. Free- and bound phenolics were identified and quantified; these included nine phenolic acids and flavonoids and their derivatives (gallic acid, gallocatechin. protocatechuic acid, catechin, vanillic acid, taxifolin, myricetin, ellagic acid, and quercetin). However, some phenolics were present only in the bound form. Furthermore, the phenolics were dominant in the brown skin.     

Effect of γ-irradiation on phenolic compounds in rice grain

Whole grain rice is rich in phenolic compounds. The effect of γ-irradiation on the main phenolic compounds in the rice grains of three genotypes (black, red, and white) was investigated. Three phenolic acids (p-coumaric acid, ferulic acid, and sinapinic acid) were identified as major phenolic compounds in all rice samples, while two anthocyanins (cyanidin-3-glucoside and peonidin-3-glucoside) were identified in pigmented grain samples. In general, γ-irradiation at most of doses could significantly (p < 0.05) decrease total phenolic acid contents in all samples and total anthocyanins contents in the black rice, but their decreases were not completely in a dose-dependent manner. Unexpectedly, 6 and 8 kGy significantly (p < 0.05) increased total contents of anthocyanins and phenolic acids in black rice. This study suggested that suitable doses of irradiation might be carefully selected and used to minimise the loss of antioxidant phenolic compounds in whole grain rice during storage.     

Phenolic profiles and antioxidant activity of litchi pulp of different cultivars cultivated in Southern China

The phenolic profiles and antioxidant activity of litchi pulp of 13 varieties were investigated. The free, bound and total phenolic contents were 66.17–226.03, 11.18–40.54, and 101.51–259.18 mg of gallic acid equivalents/100 g, respectively. The free, bound and total flavonoid contents were 16.68–110.33, 10.48–22.75, and 39.43–129.86 mg of catechin equivalents/100 g, respectively. Free phenolics and flavonoids contributed averagely 80.1% and 75% to their total contents, respectively. Six individual phenolics (gallic acid, chlorogenic acid, (+)-catechin, caffeic acid, (?)-epicatechin, and rutin) were detected in litchi pulp by HPLC. The contents of each compound in free and bound fractions were determined. Significant varietal discrepancy in antioxidant activity was also found by FRAP and DPPH scavenging capacity methods. Antioxidant activity was significantly correlated with phenolic and flavonoid contents. Thus, phenolics and flavonoids exist mainly in the free form in litchi pulp. There were significant varietal differences in phytochemical contents and antioxidant activity of litchi pulp.     

Characterization of Antioxidants Extracted from Thai Riceberry Bran Using Ultrasonic-Assisted and Conventional Solvent Extraction Methods

Riceberry bran (RBB), a waste product from rice processing, contains several antioxidants with potential health benefits. This study aims to compare the two main parameters affecting the extraction efficiency of antioxidants from RBB, namely, the extraction technique (ultrasonic-assisted extraction (UAE) and conventional solvent extraction) and solvent (ethanol and d-limonene). The highest values of total phenolic content, total flavonoid content, total anthocyanin content, and antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP) assays were detected in ethanolic extracts obtained by UAE. High-performance liquid chromatography investigation of the chemical composition of RBB revealed five major groups of antioxidants: (1) phenolic acids, including protocatechuic acid, vanillic acid, p-coumaric acid, ferulic acid, and sinapic acid; (2) flavonoids, including rutin, myricetin, and quercetin 3-glucuronide; (3) anthocyanins, including cyanidin 3-glucoside and peonidin 3-glucoside; (4) vitamin E, including γ-tocotrienol, β-tocotrienol, δ-tocopherol, γ-tocopherol, and α-tocopherol; and (5) γ-oryzanol. Protocatechuic acid exhibited the highest DPPH radical scavenging activity and FRAP values, whereas the lowest values were observed for γ-oryzanol.     

Antioxidant and antimicrobial potentials of Serbian red wines produced from international Vitis vinifera grape varieties

BACKGROUND: Antioxidant and antimicrobial potentials of Serbian red wines produced from different international Vitis vinifera grape varieties and their correlation with contents of phenolic compounds were studied by spectrophotometric and chromatographic methods. The antioxidant activity of red wines was estimated through their ability to scavenge 2,2′‐diphenyl‐1‐picrylhydrazyl free radical (DPPH^?). The red wines, gallic acid, (+)‐catechin and quercetin were screened in vitro for antimicrobial activity against Gram‐positive and Gram‐negative strains using microdilution and disc diffusion techniques. RESULTS: Excellent correlations between the contents of quercetin‐3‐glucoside (R² = 0.9463) and quercetin (R² = 0.9337) and DPPH^?‐scavenging ability of the red wines were found. Serbian red wines exhibited significant activity against Staphylococcus aureus, Listeria inocua, Micrococcus flavus, Sarcina lutea, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Salmonella enteritidis and Shigella sonnei strains, which was in correlation with their phenolic composition and antioxidant activity. The compounds gallic acid, quercetin and (+)‐catechin showed high activity against B. subtilis, S. aureus, S. lutea and M. flavus Gram‐positive and S. enteritidis and P. aeruginosa Gram‐negative strains. CONCLUSION: The results show that quercetin‐3‐glucoside and quercetin concentrations can be used as markers for the determination of antioxidant and antimicrobial potentials of red wines. Copyright © 2012 Society of Chemical Industry     

Antioxidant properties and involved compounds of daylily flowers in relation to maturity

The antioxidant properties of methanol extracts from daylily flowers during maturation were determined with antioxidant assays, including antioxidant activity, DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging, superoxide anion radical scavenging and reducing power. Antioxidant compounds, such as phenolic compounds, ascorbic acid and β-carotene were also analysed. Significant variation in antioxidant properties and involved compounds was observed between different maturity stages of daylily flowers. The highest antioxidant activity was observed at stage III (flower opening) accompanying the highest content of ascorbic acid and phenolic compounds, while no significant difference of β-carotene contents was observed among the four maturity stages. Four individual phenolics, such as (+)-catechin, chlorogenic acid, rutin and quercetin were identified and quantified by HPLC. (+)-Catechin was the main phenolic compound identified in daylily flowers, accounting for about 74.11% of total phenolics. Overall, daylily flowers at opening stage possess the highest functional benefit and thus would be the appropriate harvesting stage in view of the nutritional consideration.     

Bean cultivars (Phaseolus vulgaris L.) have similar high antioxidant capacity,in vitro inhibition of α-amylase and α-glucosidase while diverse phenolic composition and concentration

Common beans are a good source of essential nutrients such as protein, fiber, vitamins, and minerals; they also contain phenolic compounds and other phytochemicals. Phenolic compounds exhibit high antioxidant capacity that promotes health benefits by reducing oxidative stress. The objective was to compare the composition and quantity of anthocyanins and other non-colored phenolic compounds in fifteen improved bean cultivars from Mexico and Brazil and their relation to antioxidant capacity and enzymes related to type-2 diabetes. Samples were analyzed for total phenolic compounds (TP), flavonoids, antioxidant capacity (AC), tannins and total anthocyanins. Type and quantity were evaluated by HPLC-ESI-MS. Delphinidin glucoside (0.9–129.0 mg/100 g dry coat), petunidin glucoside (0.7–115.0 mg/100 g dry coat) and malvidin glucoside (0.14–52.0 mg/100 g dry coat). Anthocyanidins were positively correlated when quantified by HPLC and colorimetric analysis (R = 0.99). Cultivar Negro-Otomi presented the highest concentration of anthocyanins (250 mg/100 g dry coat). Seventeen non-colored phenolic compounds were identified among cultivars; catechin, myricetin 3-O-arabinoside, epicatechin, vanillic acid, syringic acid and o-coumaric acid, presented the highest concentrations among identified phenolic compounds. The AC of all fifteen bean cultivars did not show significant differences (p > 0.05) ranging from 185.2 (FM-67) to 233.9 (FM-199) mmol TE/g coat. Compounds in the coat extracts of pinto and black cultivars were the most efficient to inhibit α-amylase and α-glucosidase. Studied cultivars differed in composition and concentration of phenolics including anthocyanins; however, there was no effect on AC as measured by oxygen radical absorbance capacity. Black beans contained delphinidin and ferulic acid, compounds commonly used as ingredients in functional foods due to their associated health benefits.     

The phenolic compounds and the antioxidant potential of infusion of herbs from the Brazilian Amazonian region

The consumption of tea increased significantly in the past few years as a result of its health benefits as potent antioxidants in the diet. However, studies on the antioxidant compounds from Brazilian tea are scarce. Thus, the aim of this work was to evaluate the total phenolic compounds (TPC) and total flavonoids (TF) contents and the antioxidant capacity (DPPH and β-carotene/linoleic acid system) of nine herb infusions from the Amazonian region, namely agirú (Chrysobalanus icaco), açoita-cavalo (Luehea speciosa), capim-santo (Cymbopogon citratus), erva-cidreira (Lippia alba), graviola (Annona muricata L.), jucá (Libidibia ferrea), pata-de-vaca (Bauhinia ungulata), parirí (Fridericia chica) and sacaca comum (Croton spp.). These herbs were chosen based on popular knowledge and consumption. C. ferrea (68.13 mg GAE/g), L. speciosa (47.54 mg GAE/g) and C. icaco (51.30 mg GAE/g) presented the highest TPC contents, while L. speciosa (12.85 mg CE/g) and L. alba (15.42 mg CE/g) showed the highest TF contents. The highest antioxidant capacity, using both assays, was shown by L. ferrea. The three herbs with the highest TPC contents were selected to be analyzed by high performance liquid chromatography (HPLC) coupled to a diode array detector (DAD). A commercial green tea (Camellia sinensis) was also analyzed as a reference. The main compounds tentatively identified were gallic acid (0.45 mg/g), myricetin (0.78 mg/g) and quercetin (0.14 mg/g) in C. icaco; (+)-catechin (1.20 mg/g) and quercetin (0.14 mg/g) in L. speciosa; gallic acid (0.59 mg/g) and quercetin (0.13 mg/g) in C. ferrea; and gallic acid (0.24 mg/g), (−)-epicatechin (2.44 mg/g), (+)-catechin (0.68 mg/g) and quercetin (0.66 mg/g) in green tea. Among the nine studied herbs, the importance of L. ferrea should be pointed out since it presented the highest TPC content and antioxidant capacity and its gallic acid content was much higher than that of green tea.     

Phenolic profile and antioxidant properties of a crude extract obtained from a brewery waste stream

The main aims of this study were to determine the phenolic profile of a crude extract obtained (at pilot scale) from a brewery waste stream and to evaluate the antioxidant activity of the extract. The total phenolic content was determined by the Folin–Ciocalteu assay, which revealed that 50% of the extract comprised phenolic compounds. The polyphenols, identified and quantified by RP-HPLC–DAD and HPLC-ESI–TOF-MS, were mainly flavonoids (catechin, epicatechin, gallocatechin, epigallocatechin, quercetin) and phenolic acids (ferulic acid, p-coumaric acid, caffeic acid, protocatechuic acid). The crude extract displayed a high DPPH radical scavenging activity (0.18 g/L), similar to that of BHA (0.248 g/L) and higher than that of BHT (2.54 g/L). All three tested products displayed a similar ability to decrease oxidative bleaching of β-carotene (antioxidant activity coefficient of 623.8 for the crude extract, 653.3 for BHA, 559.6 for BHT). This type of brewery waste stream may be a promising source of natural antioxidants to replace the synthetic antioxidants currently used in the food industry.     

Riboflavin Phototransformation on the Changes of Antioxidant Capacities in Phenolic Compounds

Eight phenolic compounds including: p‐coumaric acid, vanillic acid, caffeic acid, chlorogenic acid, trolox, quercetin, curcumin, and resveratrol were treated with riboflavin (RF) photosensitization and in vitro antioxidant capacities of the mixtures were determined by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), 2,2’ azino bis(3‐ethylbenzothiazoline‐6‐sulphonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) assays. Mixtures containing p‐coumaric acid and vanillic acid under RF photosensitization showed increases in ferric ion reducing ability and radical scavenging activity of DPPH, whereas mixtures of other compounds had decreases in both radical scavenging ability and ferric reducing antioxidant power. Hydroxycoumaric acid and conjugated hydroxycoumaric and coumaric acids were tentatively identified from RF photosensitized p‐coumaric acid, whereas dimmers of vanillic acid were tentatively identified from RF photosensitized vanillic acid. RF photosensitization may be a useful method to enhance antioxidant properties like ferric ion reducing abilities of some selected phenolic compounds.     

Phenolic Profiles and Total Antioxidant Capacity of Marketed Beers in Serbia

The aim of this research was to determine the total phenolic and flavonoid contents as well as to measure antioxidant activity of 24 different commercial beers consumed in Serbia. The major phenolic acids (gallic acid, protocatechuic acid, 4-hydroxybenzoic acid, 2,5-dihydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, sinapic acid, salicylic), (+)-catechin, and (-)-epicatechin were also determined by high pressure liquid chromatography method using a photodiode array detector. Gallic acid, ferulic acid, and protocatechuic acid are the most abundant phenolic acids in all samples, followed by (+)-catechin. The total phenolic content was determined using the Folin-Ciocalteu assay. The total flavonoids were measured using spectrophotometrics as the aluminum chloride assay. The results showed that the highest total phenolic and flavonoid contents were established in dark and light beer samples. 2,2-Diphenyl-1-picrylhidrazyl radical scavenging activity, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) radical cation scavenging activity, and ferric reducing/antioxidant power were used to assess the antioxidant potential of beers. These assays, based on different chemical mechanisms, were selected to take into account the wide variety and range of action of antioxidant compounds present in selected beer samples. All beers showed antioxidant power, but a wide range of antioxidant capacities was observed. Statistical differences between ferric reducing-antioxidant power and the other two antioxidant capacity assays were confirmed. This study will be useful for the appraisal of phenolic profile and antioxidant activities of various beers, and it will also be of interest for people who like drinking this beverage.     

Determination of 13 Phenolic Compounds in Rice Wine by High-Performance Liquid Chromatography

Rice wines are widely consumed by the general public in Asian countries, while comprehensive studies focused on the individual phenolic compounds in rice wines are limited. A rapid method for simultaneous determination of 13 phenolic compounds in rice wines by high-performance liquid chromatography (HPLC) was developed and validated, and the phenolic compounds in commercial rice wine samples (Chinese rice wine, Japanese sake, and Korean makgeolli) were determined in this paper. The identified compounds contained gallic acid (GA), protocatechuic acid (PRCA), vanillic acid (VA), syringic acid (SRA), caffeic acid (CA), ferulic acid (FA), p-coumaric acid (pCA), sinapic acid (SA), chlorogenic acid (CHA), (+)-catechin (CAT), (?)-epicatechin (EPI), quercetin (QUE), and rutin (RUT). Phenolics were separated with a C18 reversed-phase column at 38 °C by gradient elution using 3 % acetic acid aqueous solution (solvent A) and acetonitrile (solvent B) (0 min, 5 % B; 5 min, 8 % B; 10 min, 15 % B; 20 min, 25 % B; and 25 min, 5 % B) as the mobile phase at 280 nm with flow rate of 1.0 mL min^?1. With direct injection of rice wine samples, the chromatograms of all analytes were observed within 20 min, all calibration curves were linear (R ²?>?0.995) within the range, limits of detection (LOD) ranged from 0.02 to 0.06 μg mL^?1, and good recoveries (88.07–106.80 %) and precision (relative standard deviation (RSD)?<?5.36 % ) were obtained for all compounds. This method was applied to quantify phenolic compounds in commercial rice wine samples (Chinese rice wine, Japanese sake, and Korean makgeolli), and good separation peaks were observed and catechin was the predominant phenolic in the samples. The average values of total phenolic contents of the three groups of rice wine were significantly different (p?<?0.01). In conclusion, this procedure can be used to determine the phenolic compounds in various types of rice wines, as well as to characterize and differentiate rice wine samples.     

Antioxidant properties and polyphenolics composition of common hedge hyssop (Gratiola officinalis L.)

The antioxidant potential of Gratiola officinalis was evaluated by the off-line and on-line HPLC/UV/DPPH radical scavenging assays, phytochemical composition was analyzed by LC/MS. On-line method was validated by using reference antioxidants and linear dependence was found between their concentration and radical scavenging peak area. Radical scavenging capacity (RSC) of methanol and acetone extracts expressed in their concentration required to scavenge 50% of DPPH^? was 0.10% and 0.13%, respectively; the RSC in ABTS^?+ assay was 1093 ± 104 and 746 ± 18 μM of trolox equivalents in 1 g, respectively. Good correlation was observed between total amount of phenolic compounds and RSC. Preliminary HPLC/UV/MS analysis revealed that the main compounds possessing antioxidant activity in the extracts might be phenylpropanoid glycosides; UPLC/UV/ESI-QTOF-MS analysis suggested 15 structures: 2,5-dihydroxy-p-benzenediacetic and caffeic acids, apigenin 6,8-di-C-β-d-glucopyranoside (vicenin-2), apigenin 8-C-α-l-arabinoside 6-C-β-d-glucoside, (shaftoside), forsythoside B, arenarioside, verbascoside (acteoside), amioside, quercetin-6-O-(2-O-acetyl-glucopyranosyl)-glucopyranoside, isoverbascoside, quercetin glucuronide, linariifolioside, methoxy luteolin-7-O-(6-O-acetyl-glucopyranosyl)-glucopyranoside, methoxy luteolin-glucuronide and luteolin glucuronide.     

HPLC-analysis of polyphenolic compounds in Spanish white wines and determination of their antioxidant activity by radical scavenging assay

A high-performance liquid chromatographic method coupled with UV and fluorescence detectors for the determination of polyphenols in white wines samples is reported. The proposed method was validated regarding linearity, repeatabilities within day and between days, recoveries and polyphenol stabilities.Eleven phenolic compounds including, flavanols and flavanols dimmers (procyanidins), hydroxycinnamates, flavonols and stilbene derivatives were identified and quantified. Samples were injected into the chromatograph directly without previous treatment.The in-house method validation provided good results with respect to repeatabilities (within day (RSD ? 4%) and between days (RSD ? 5%)) and recoveries (?97.3%).In the second part of the work the antioxidant activity of the wine samples was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. The correlation between specific polyphenols and the antioxidant activity in samples was also investigated.     

Antioxidant properties of commercial wild rice and analysis of soluble and insoluble phenolic acids

To investigate the antioxidant properties of commercial wild rice, identify and quantify soluble and insoluble phenolic acids in wild rice whole grain, the alkaline hydrolysates from crude methanol extracts (soluble fraction) and residues (insoluble fraction) were separately analysed by high performance liquid chromatography (HPLC) coupled with photodiode array detection (PAD) and quadrupole-time of flight (Q-TOF) mass spectrometry (LC–MS). The antioxidant activity of wild rice methanol extract was found to be up to 10 times greater than that of white rice (control sample) according to their 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and oxygen radical absorbance capacity (ORAC). Ferulic acid was found as the most abundant phenolic acid (up to 355 mg/kg) followed by sinapic acid in wild rice. They both occurred mainly in the insoluble form. Other monomeric phenolic acids present in wild rice consisted of p-coumaric, vanillic, syringic, and p-hydroxybenzoic acids, along with two phenolic acid aldehydes (p-OH-benzaldehyde and vanillin). They were present in both soluble and insoluble forms. Phenolic acid dehydrodimers are cell wall bound and only appeared in the insoluble fractions featured by diferulic acids (DiFA) and disinapic acids (DiSA). The chemical structures of DiFA included 8-8′, 5-5′, 8-O-4′, and 8-5′ (benzofuran form) coupled dimers, with 8-O-4′ as the predominant form (up to 34 mg/kg). DiSA only appeared as 8-8′-coupled products with the linear isomers in the most quantities (up to 19 mg/kg). The DPPH free radical scavenging activities of soluble and insoluble fractions suggest that the antioxidant activity of wild rice is partially attributed to its phenolic acid profile.