Comparative analyses of total phenols,flavonoids, saponins and antioxidant activity in yellow soy beans and mung beans

Total phenol, flavonoid and saponin content of soy bean and mung bean were systemically compared in order to evaluate their contribution to overall antioxidant activity. Mung bean extract possessed significantly higher total phenol (2.03 GAE g^?1 vs. 1.13 GAE g^?1) and flavonoid contents (1.49 GAE g^?1 vs. 0.41 CAE g^?1) than soy bean extract, while the saponin content of the soy beans was 4.5 times greater than that of the mung beans. In several antioxidant assays including DPPH and ABTS radical scavenging, FRAP, SOD‐like activity, and a β‐carotene bleaching assay, mung bean extract consistently showed significantly greater antioxidant activity than soy bean extract. The specific antioxidant activity, which was evaluated at the same phenolic content suggested that the phenolic compounds present in the mung bean extract were not only of greater quantity but also had better quality to eliminate radicals. The radical scavenging activities of saponins were only marginal.     

Oil content,phenolic profiling and antioxidant potential of Tunisian olive drupes

BACKGROUND: The aim of this work was to investigate the effect of the maturation process of the olive fruit on oil content, phenolic profile and antioxidant activity of four Tunisian cultivars (Zelmati, Chemchali, Chemlali and Chétoui). RESULTS: The average oil content of the studied varieties ranged between 17.50% and 20.25% at the first stage of maturation and from 30.20% to 35% in the last harvest. Qualitative and quantitative analysis of phenolic compounds were carried out using HPLC and LC‐MS/MS. Twenty‐six biophenolic compounds were identified. In all samples, hydroxytyrosol and oleuropein were the major compounds identified while rutin and luteolin 7‐O‐glucoside were the two main flavonoids. The total phenolic content varied from 3.46 to 4.30 g kg^?1 at the first stage of maturation and from 8.71 to 11.52 g kg^?1 of fruit fresh weight at the last maturation phase. Total flavonoid content reached 432.80 mg kg^?1. The antioxidant activity of the extract was evaluated by DPPH and ABTS assays. The IC₅₀ values of the olive extracts ranged from 2.69 to 10.96 µg L^?1 and from 2.15 to 3.03 mmol L^?1 trolox equivalent at the last stage of maturation. CONCLUSION: A relationship between the changes in phenolic content and the physicochemical changes in Tunisian olive fruit during maturation was established. These findings could be used for controlling the production processes and correlating the oil sensorial characteristics to the polyphenolic pattern. Copyright © 2010 Society of Chemical Industry     

Phenolics and antioxidant activity of lentil and pea hulls

Hulls obtained by pilot-scale dehulling process from green and red lentils and yellow peas were fractionated into hulls (> 500 ??m) and residues (< 500 ??m). These fractions together with the corresponding whole seeds were extracted with four solvents, aqueous (70%) acetone, (80%) ethanol, hot water (70-80 °C) and water (22 ± 1 °C) and evaluated for antioxidant activity in relation to phenolic contents. Aqueous acetone (70%, v/v) extracted the highest level of total phenolics at about 87 mg of catechin equivalent per gram of sample from lentil hulls followed by hot water, water and aqueous ethanol (80%, v/v). Red lentil hull with maximum concentration of phenolic compounds exhibited the strongest antioxidant activity of 260 mg (1040 ??M) trolox equivalent/g hull. Hot water and water extracted significantly higher total phenolics from whole pulse and their residue than other solvents, but with weaker antioxidant activity. Aqueous ethanol was always the best extractant of phenolic antioxidant from yellow pea irrespective of its millstream. The most potent phenolic antioxidant was obtained from water extract of green and red lentil hulls, followed by those extracted with ethanol, acetone, and hot water. Total phenolic content was highly correlated with antioxidant activity of pulses and its millstreams.     

Nutritional composition and antioxidant activity in hazelnut shells from US‐grown cultivars

The hard shell of a hazelnut is a major waste of the hazelnut industry. The chemical composition, phenolic compounds (total phenolics, tannins and condensed tannins), antioxidant activity (DPPH and ABTS free‐radical scavenging assays), and the relationships between phenolic compounds and antioxidant activities of the hazelnut shells from twelve US grown cultivars were investigated to for potential commercial development. Crude fibre accounted for over 85% of total carbohydrate. The shells contained high concentrations of phenolic compounds. Concentrations of phenolic constituents and ABTS^?+ ‐scavenging capacities were significantly higher (P > 0.05) in the Oregon cultivars than their Nebraska counterparts. There were significant positive correlations between ABTS^?+ scavenging capacities and the phenolic compounds, whereas DPPH^? ‐scavenging capacity demonstrated a weak negative correlation with ABTS^?+ scavenging capacity and the phenolics. The results suggest that hazelnut hard shell may serve as a potential source of natural antioxidants for food applications.     

Biological activities of the essential oil and methanolic extract of Micromeria fruticosa (L) Druce ssp serpyllifolia (Bieb) PH Davis plants from the eastern Anatolia region of Turkey

The in vitro antimicrobial and antioxidant activities of the essential oil and methanolic extract of Micromeria fruticosa ssp serpyllifolia as well as the composition of the essential oil were examined. The essential oil exhibited activity against 14 bacteria, three fungi and a yeast, with minimal inhibitory concentration (MIC) values ranging from 31.25 to 125 µl ml^?1, whilst the methanolic extract was inactive. Antioxidant activity was measured by two methods, namely scavenging of the free radical DPPH and inhibition of linoleic acid oxidation. The methanolic extract exhibited significant antioxidant activity in both assays, providing 50% inhibition at 70.9 ± 0.5 µg ml^?1 concentration in the DPPH assay and inhibiting linoleic acid oxidation to 59% at 2 mg ml^?1 concentration, whilst the essential oil showed activity only at higher concentrations. The gallic acid equivalent total phenolic content of the methanolic extract was found to be 55.2 ± 2.00 µg mg^?1 dry weight extract (5.5% w/w). The chemical composition of the hydrodistilled essential oil was analysed by means of GC/MS. Twenty‐nine constituents were identified, the main ones being piperitenone (50.61%) and pulegone (29.19%). Copyright © 2004 Society of Chemical Industry     

Antioxidant and antimicrobial activities of Polygonum cognatum Meissn extracts

The antioxidant activities, reducing powers, 2,2‐diphenyl‐l‐picrylhydrazyl (DPPH) radical‐scavenging activities, total phenolic compound contents and antimicrobial activities of ether, ethanol and hot water extracts of Polygonum cognatum Meissn were studied in vitro. The highest antioxidant activity was found in the water extract. However, there were no statistically significant differences among 15 µg ml^?1 extract‐containing samples in linoleic acid emulsion (0.02 M , pH 7.0) during 120 h of incubation (P > 0.05). The reducing power of the water extract was the highest, but its reducing power was markedly lower than that of ascorbic acid. The highest DPPH radical‐scavenging activity was found in the water extract, with 50% DPPH radical scavenging at a concentration of 100 µg ml^?1 dried water extract, while at the same concentration of dried ethanol extract the value was 12%. Surprisingly, no DPPH radical‐scavenging activity was observed in the ether extract. The concentrations of phenolic compounds found were 0.48, 0.50 and 0.01 µg ml^?1 gallic acid equivalent in 10 µg ml^?1 water, ethanol and ether extracts respectively. The ether and ethanol extracts showed antimicrobial activity against Staphylococcus aureus and Bacillus subtilis. The water extract did not show antimicrobial activity against the studied micro‐organisms. © 2002 Society of Chemical Industry     

Characterisation of phenolic acids,flavonoids, proanthocyanidins and antioxidant activity of water extracts from seed coats of marama bean [Tylosema esculentum] – an underutilised food legume

Freeze‐dried aqueous phenolic extracts with possible application as natural antioxidant functional food ingredients were prepared from marama bean seed coats by extracting with water. Phenolic acids, flavonoids and proanthocyanidins in the extracts were characterised by HPLC/MS. The major flavonoids were the flavanols methyl (epi)afzelechin‐3‐O‐gallate (40%) and methyl (epi)catechin‐3‐O‐gallate (28%), and the major phenolic acid was gallic acid (10%). Proanthocyanidins in the extracts were predominantly prodelphinidins composed of epicatechin‐3‐O‐gallate and epigallocatechin present as major terminal and extension units and epigallocatechin‐3‐O‐gallate and epicatechin present as minor extension unit constituents. The polymer structure was found to be unique compared with other legumes because of the high percentage of galloylated units. Extracts showed a high DPPH free radical scavenging activity (707 μmol TE g^?1), protective effect against AAPH‐induced human red blood cell haemolysis and copper‐catalysed human LDL oxidation suggesting that the extracts may have potential health benefits.     

Optimisation of spray drying process parameters for low‐fat honey‐based milk powder with antioxidant activity

The purpose of this study was to optimise process parameters to prepare spray‐dried honey‐based milk powder containing functional properties of honey. Experimental design with temperature (180 to 200 °C), honey concentration (5–15%) and feed flow rate (8–10 rpm) as independent variables was studied to investigate the effect on product responses. Results showed that increasing the temperature resulted in powder with lower moisture, bulk density, antioxidant activity, total phenolic contents, total flavonoid contents and higher water solubility index. Increasing feed flow rate resulted in higher moisture, bulk density, antioxidant activity, reduced water solubility index, total phenolic content and total flavonoid content, whereas increasing honey concentration resulted in increase in antioxidant activity, total phenolic content and total flavonoid content. The moisture content, bulk density, water solubility index, DPPH scavenging activity, total phenolic content and total flavonoid content were 3.27%, 0.44 g cc^?1, 96.67 g g^?1, 17.45%, 2.54 GAE g^?1 powder and 1.40 RE g^?1 powder, respectively.     

Evaluation of chemical constituents and antioxidant activity of sweet cherry (Prunus avium L.) cultivars

This research was undertaken to evaluate the sugars, organic acids, phenolic compositions and antioxidant capacities of sweet cherry cultivars (Van, Noir de Guben, Larian and 0‐900 Ziraat) grown in Turkey. High‐performance liquid chromatographic methods were used to identify and quantify four sugars (sucrose, glucose, fructose and sorbitol) and four organic acids (malic, citric, shikimic, and fumaric acid). The major organic acid was found as malic acid (8.54–10.02 g kg^?1 of FW). With regard to sugars, glucose was present in the largest amounts (44.71–48.31 g kg^?1 of FW) for sweet cherry cultivars. The sum of sugars ranged from 103.87 (Larian) to 113.13 g kg^?1 of FW (0‐900 Ziraat) and that of organic acids from 12.01 (0‐900 Ziraat) to 14.17 g kg^?1 of FW (Noir de Guben). A total of eleven phenolic compounds were identified and quantified in sweet cherry cultivars, including hydroxycinnamic acids (3), anthocyanins (5), flavan‐3‐ols (2) and flavonol (1) compounds. Total phenolic contents ranged from 88.72 (Van) to 239.54 (Noir de Guben) mg/100 g of FW, while antioxidant activities ranged from 2.02 to 7.75 μm Trolox equivalents g^?1 of FW.     

Effect of fermentation by Bacillus subtilis on antioxidant and cytotoxic activities of black rice bran

Black rice bran was fermented with Bacillus subtilis KU3 isolated from Korean traditional food, Kimchi. Antioxidant and cytotoxic activities of the fermented black rice bran were investigated. Total phenolic and anthocyanin contents decreased from 171.54 mg GAE g^?1 and 2.31 mg g^?1 to 139.13 mg GAE g^?1 and 2.12 mg g^?1, respectively, after fermentation. Antioxidant activities determined by 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging, β‐carotene bleaching and ferric thiocyanate assay were correlated with total phenolic and anthocyanin contents. Non‐fermented black rice bran extract (NFBE) showed greater antioxidant activities than fermented black rice bran extract (FBE). Cytotoxic activities measured by MTT assay showed that both NFBE and FBE had over 50% activities. The cytotoxic activities of FBE against MCF‐7 and HeLa cells were 71.65% and 68.07%, respectively, at 8.0 mg mL^?1, but those of NFBE were lower than 50%. These results suggested that the cytotoxic activity of black rice bran improved through fermentation, while antioxidant activity reduced.     

Antioxidant and Anti‐inflammatory Activities of Methanol Extracts of Tremella fuciformis and Its Major Phenolic Acids

Methanol extract subfractions of the edible white jelly mushroom (Tremella fuciformis), were assessed for the following antioxidant properties: ABTS⁺ radical scavenging activity, 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging activity, and inhibitory activity of human low‐density lipoprotein (LDL) oxidation. Among the subfractions tested, the chloroform subfraction exhibited the strongest antioxidant activity, with the highest total phenolic content (66.31 μg CAE/mg extract) and flavonoids content (5.12 μg QE/mg extract). The ABTS⁺ radical scavenging activity of the chloroform subfraction was 7.89 μmol trolox/mg extract, which was the highest among all subfractions. This subfraction also showed the highest DPPH radical scavenging activity and inhibitory activity of LDL oxidation. In addition, the chloroform subfraction demonstrated anti‐inflammatory activity through inhibition of nitric oxide production and inducible nitric oxide synthase expression in RAW 264.7 cells. Major phenolic acids from the mushroom extract were identified as 4‐hydroxybenzoic acid (323 mg/kg dry weight of mushroom), gentisic acid (174 mg/kg dry weight of mushroom), and 4‐coumaric acid (30 mg/kg dry weight of mushroom).     

Antioxidant properties of various solvent extracts of potato peel,sugar beet pulp and sesame cake

BACKGROUND: Growing interest in the replacement of synthetic food antioxidants by natural ones has fostered research on vegetable sources and screening of raw materials to identify new antioxidants. The food‐processing industry generates substantial quantities of phenolic‐rich by‐products that could be valuable natural sources of antioxidants. In this study the antioxidant properties and total phenolic, flavonoid and flavonol contents of three industrial by‐products, sugar beet pulp, sesame cake and potato peel, extracted with various solvents were examined. Since different antioxidant compounds have different mechanisms of action, several methods were used to assess the antioxidant efficacy of extracts. RESULTS: Among the six solvents tested, methanol gave the highest extract yield of potato peel and sugar beet pulp, while diethyl ether gave the highest extract yield of sesame cake. Methanol exhibited the highest extraction ability for phenolic compounds, with total phenolics amounting to 2.91, 1.79 and 0.81 mg gallic acid equivalent g^?1 dry weight in potato peel, sugar beet pulp and sesame cake extracts respectively, and also showed the strongest antioxidant capacity in the three assays used. All three methods proved that potato peel extract had the highest antioxidant activity owing to its high content of phenolic compounds and flavonoids. CONCLUSION: On the basis of the results obtained, potato peel, sugar beet pulp and sesame cake extracts could serve as natural antioxidants owing to their significant antioxidant activity. Therefore they could be used as preservative ingredients in the food and/or pharmaceutical industries. Copyright © 2009 Society of Chemical Industry     

Phenolic profile and antioxidant activity of highbush blueberry (Vaccinium corymbosum L.) during fruit maturation and ripening

The phenolic profile and quantitative composition of blueberries as well as the corresponding antioxidant activity of blueberries is well documented. Unfortunately, little is reported on the development of phenolic compounds and antioxidant activity during fruit maturation and ripening. In the present study, the total phenolic content and main phenolic compounds of four highbush blueberry cultivars (Vaccinium corymbosum L.) were analyzed at five stages of maturation and ripening. Antioxidant activity was screened with electron spin resonance spectrometry and trolox equivalent antioxidant capacity (TEAC) assay. An adequate picture of phenolic compounds developed during maturation and ripening was determined using HPLC-DAD. Anthocyanins of all varieties increased during successive harvest stages; meanwhile flavonols and hydroxycinnamic acids decreased from unripe green to ripe blue stage of berry ripening. Blueberry antioxidant activity, as well as total phenolic content tended to decrease during ripening.     

Lipophilic phenols partially explain differences in the antioxidant activity of subfractions from methanol extract of camellia oil

The crude methanol extract (ME) from camellia oil was fractionated by serial benzene, ether, EtOAc and n-BuOH, divided into five subfractions designated as SF1–5. The obtained fractions as well as ME were evaluated for their antioxidant activities using DPPH assay, and their phenolic constituents were isolated using silica gel column chromatography and analysed by TLC, RP-HPLC–PDA, UPLC-ESI–MS and GC–MS. Results showed that the content of total phenolics (TPs) of ME, determined by the Folin–Ciocalteu method, was estimated to be 79.5?±?10.2?mg of p-hydroxybenzoic acid equivalent/kg oil, while that of the total flavonoids was 8.98?±?0.54?mg of rutin equivalent/kg oil. ME exhibited pronounced radical-scavenging activity against the stable DPPH radical (with an antioxidant capacity IC₅₀ value of 52.37?μg/mL), and three subfractions (SF1–3) separated from ME contributed the most significant activity with IC₅₀ of 28.41, 17.42 and 43.17?μg/mL, respectively. Consistent with the different capacity of scavenging DPPH radicals, the subfractions from ME showed different composition and contents of phenolic compounds as detected by TLC, RP-HPLC–PDA, UPLC-ESI–MS and GC–MS. Kaempferol, as well as a number of volatile phenolic compounds, was first identified from camellia oil. Results showed that the presence of phenolic compounds and flavonoids in each extracts may be responsible for its individual antioxidant activity, and the lipophilic phenolic fractions would likely account for a great part of the antioxidant properties of the oil.     

Antioxidant activity and phenolic content of lentils (Lens culinaris), chickpeas (Cicer arietinum L.), peas (Pisum sativum L.) and soybeans (Glycine max), and their quantitative changes during processing

Total phenolic content (PC) was ～12 mg g^?1 in lentils, 2.2 mg g^?1 in chickpeas, 2.3 mg g^?1 in soybeans, 2.5 mg g^?1 in yellow peas and 1.2 mg g^?1 in green peas. Total antioxidant activity (AA) determined by ABTS (2,2′‐azinobis‐3‐ethyl‐benzthiazoline‐6‐sulfonic acid) assay was highest in lentils at around 14 μmol Trolox equivalent antioxidant capacity (TEAC) g^?1 and lowest in green peas at 1.9 μmol TEAC g^?1. Bound phytochemicals contributed to 82–85% total AA in lentils. Free phytochemicals contributed more to total AA in chickpeas, yellow peas, green peas and soybeans than bound phytochemicals. AA and PC was reduced by ～80% in lentils and <30% in yellow peas by decortication, by 16–41% in lentils, chickpeas and peas by cooking, and by 22–42% in lentils by soaking. Total AA was significantly correlated with total PC. Soybeans had the greatest ability to scavenge free radicals, inhibit lipid peroxidation and chelate metals among the legumes tested. Different legumes exhibited different AA mechanisms.     

Antioxidant activity of the ethanolic extract from the bark of Chamaecyparis obtusa var. formosana

BACKGROUND: Chamaecyparis obtusa var. formosana (Taiwan hinoki) is an endemic conifer in Taiwan and the purpose of this study is to evaluate the antioxidant activity of various fractions obtained from the bark of this plant material. The ethanolic extract of the bark was sequentially separated into three fractions, including n‐hexane, ethyl acetate and ethanol soluble fractions, by liquid–liquid partition. Then the antioxidant activities of crude extract and three fractions along with 13 subfractions obtained from the ethyl acetate (EA) soluble fraction were tested for several antioxidant assays. RESULTS: The total phenolic content of the samples varied from 27.71 to 102.86 mg GAE g^?1 dry weight for fractions, and from 49.94 to 206.46 mg GAE g^?1 for subfractions (where GAE is milligrams of gallic acid per gram of extract). The Trolox equivalent antioxidant capacity (TEAC) ranged from 0.15 to 0.26 mmol L^?1 Trolox equivalents. The EA soluble fraction was found to be the best antioxidant‐rich fraction in terms of DPPH and reducing power assays. With further data analysis it was found that there was a positive correlation between the total phenolic content of extracts and TEAC is R² = 0.61. CONCLUSION: Results from various antioxidant assays showed that the EA fraction possessed strong antioxidant activity. This would provide additional information about the antioxidant activity of bark extract of this plant species. Copyright © 2008 Society of Chemical Industry     

Characterisation of the phenolic and flavonoid fractions and antioxidant power of Italian honeys of different botanical origin

BACKGROUND: Twenty‐seven Italian honey samples of different floral origin were analysed for total phenolic and flavonoid contents by a spectrophotometric method and for antioxidant power and radical‐scavenging activity by the ferric‐reducing/antioxidant power (FRAP) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) assays respectively. In addition, the phenolic and flavonoid profiles were analysed using high‐performance liquid chromatography with UV detection (HPLC‐UV). RESULTS: The results of this study showed that honey contains copious amounts of phenolics and flavonoids. HPLC‐UV analysis showed a similar qualitative polyphenolic profile for all honey samples analysed. The main difference among samples was in the contribution of individual analytes, which was affected by floral origin. Total phenolic and flavonoid contents varied from 60.50 to 276.04 mg gallic acid equivalent kg^?1 and from 41.88 to 211.68 mg quercetin equivalent kg^?1 respectively. The antioxidant capacity was high and differed widely among samples. The FRAP value varied from 1.265 to 4.396 mmol Fe²⁺ kg^?1, while the radical‐scavenging activity expressed as DPPH‐IC₅₀ varied from 7.08 to 64.09 mg mL^?1. Correlations between the parameters analysed were found to be statistically significant (P < 0.05). CONCLUSION: The present study shows that honey contains high levels of phenolics and flavonoids and that the distribution of these compounds is influenced by the honey's floral origin. Copyright © 2009 Society of Chemical Industry     

Buckwheat (Fagopyrum esculentum Moench) Grain and Fractions: Antioxidant Compounds and Activities

Abstract: Buckwheat (Fagopyrum esculentum Moench) is an alternative crop belonging to the Polygonaceae family. In comparison to antioxidant activity of frequently used cereals, buckwheat has been reported to possess higher antioxidant activity (AOA), mainly due to high rutin content. The objective of this work was to determine the main antioxidant compounds and AOA of buckwheat grain fractions (whole grain, hull, and groat). Buckwheat grain fractions were extracted with ethanol/water (80/20, v/v), followed by determination of total phenolic and flavonoid content. Quantification of phenolic compounds and tocopherols was performed by high‐performance liquid chromatography (HPLC). The AOA was estimated by 2 direct electron spin resonance (ESR) and 4 indirect (spectrophotometric) tests. Significantly higher contents of total phenolics and total flavonoids were found in buckwheat hull than in whole grain and groat. Protocatechuic, syringic, and sinapic acid, rutin, and quercetin were found in all tested fractions, whereas vanilic acid was found in whole grain and hull. The content of total tocopherols in investigated samples ranged from 23.3 mmol/g for hull to 61.8 mmol/g for groat. Hull was superior in scavenging activity on 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH^?), hydroxyl (^?OH), and superoxide anion (O₂^?‐) radicals, reducing activity, AOA by β‐carotene bleaching method, and chelating activity on Fe²⁺ as evidenced by its lower IC₅₀ value. Obtained results can broaden the utilization of buckwheat, especially a share of hull in whole grain flour production. Practical Application: Obtained results suggest possibility to supplement the whole grain buckwheat flour with hull, which leads toward better usage of by‐products in buckwheat production, and enhancement of antioxidant potential of the final product.     

Rice kernel phenolic content and its relationship with antiradical efficiency

Plant phenolics exert beneficial effects on human health and may also prevent oxidative deterioration of food. Two field experiments were carried out for characterising phenolics in rice. The first assay was conducted in 1999 and 2000 in Beaumont, TX and included five light‐brown, two purple and 10 red pericarp coloured cultivars. ‘Bran colour’ was highly statistically significant for both bran phenolic concentration and antiradical efficiency (p < 0.001). ‘Year’ and its interaction with bran colour were not significant for the analysed traits, suggesting that seasonal differences and their interactions may not affect phenolic content or antiradical efficiency. The accessions ranged from 3.1 to 45.4 mg gallic acid equivalents (GAE) g^?1 bran and from 10.0 to 345.3 µM trolox equivalents (TE) g^?1 bran for total phenolic content and antiradical efficiency respectively. The light‐brown bran genotypes exhibited the lowest values for phenolic content and antiradical efficiency, whereas red bran ones displayed ca 10 times higher total phenolic content and more than 50 times higher tannin content than light‐brown ones. The two purple lines showed either low or high values for the studied traits. Antiradical efficiency of rice bran extracts was highly positively correlated with total phenolic content (r = 0.99***), suggesting that phenolics are the main compounds responsible for the free radical‐scavenging activity in rice bran extracts. In the second field experiment (Stuttgart, AR, 2001 and Beaumont, TX, 2000), 133 coloured rice cultivars were analysed for total phenolic content in whole grain. The accessions showed a large variation for total phenolics, ranging from 0.69 to 2.74 mg GAE g^?1 grain. The data confirmed previous results suggesting bran colour as the main factor affecting phenolic concentration in rice kernel and seasonal effects and their interactions as not significant. The results also confirm that within red and purple bran groups can be found the highest phenolic concentrations in rice kernel. Published in 2004 for SCI by John Wiley & Sons, Ltd.     

绿豆皮中黄酮类化合物的抗氧化活性及其结构分析

本文旨在分析绿豆皮中黄酮类化合物的抗氧化活性及其结构。采用20%、40%、60%、80%乙醇对绿豆皮黄酮粗提物进行梯度洗脱纯化,以总抗氧化能力（total antioxidative capability,T-AOC）、1,1-二苯基-2-三硝基苯肼（1, 1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除能力、2,2′-联氨-双-3-乙基苯并噻唑啉-6-磺酸（2, 2′-azinobis-3-ethylbenzothia zoline-6-sulphonic acid,ABTS）自由基清除能力、羟自由基清除能力等为指标,筛选出具有最高抗氧化活性的组分,并对其进行结构鉴定。结果表明,60%洗脱液中绿豆皮黄酮的抗氧化能力最强,其DPPH自由基清除能力为48.03%;ABTS+自由基清除能力为57.53%;羟自由基清除能力为12.02%;T-AOC的抗氧化活性为207.64 U/mL,显著高于其他洗脱液（P<0.05）。绿豆皮中具有最强抗氧化活性的黄酮类化合物分别包括牡荆素(vitexin)、异牡荆素(isovitexin)及圣草酚-6-C-β-D-吡喃葡萄糖苷(eriodictyol-6-C-β-D-glucopyranoside)。