Antioxidant activity of Potentilla fruticosa

The molecular structures of the radical scavenging compounds present in extracts of Potentilla fruticosa blossoms were elucidated and the antioxidant activities of various extracts were determined. The activities of the different fractions were monitored by off‐line and on‐line RP‐HPLC DPPH^? and ABTS^?+ scavenging methods. Twelve compounds were isolated and identified, namely ellagic acid, catechin, quercetin‐3‐β‐glucopyranoside, quercetin‐3‐β‐galactopyranoside, quercetin‐3‐β‐rutinoside, quercetin‐3‐β‐glucuronopyranoside, quercetin‐3‐α‐arabinofuranoside, kaempferol‐3‐β‐rutinoside, kaempferol‐3‐O‐β‐(6″‐O‐(E)‐p‐coumaroyl)glucopyranoside, rhamnetin‐3‐β‐glucopyranoside and rhamnetin‐3‐β‐galactopyranoside. The radical scavenging activity of each isolated compound was measured using DPPH^? and ABTS^?+ assays and compared with the activity of rosmarinic acid. Catechin and ellagic acid were found to be the most active radical scavengers. The antioxidant properties of plant fractions were assessed in model systems by measuring superoxide anion and hydrogen peroxide scavenging, β‐carotene bleaching, hexanal production in edible oil, peroxide formation, and the increase in UV absorbance in the course of oxidation. Copyright © 2004 Society of Chemical Industry     

Identification and in vitro biological activities of flavonols in garlic leaf and shoot: inhibition of soybean lipoxygenase and hyaluronidase activities and scavenging of free radicals

We isolated four flavonols from garlic (Allium sativum L) leaf and shoot and measured the in vitro antioxidant activity of the isolated flavonols and their aglycones. The chemical structures of the compounds were shown to be quercetin 3‐O‐β‐D ‐glucopyranoside (isoquercitrin), quercetin 3‐O‐β‐D ‐xylopyranoside (reynoutrin), kaempferol 3‐O‐β‐D ‐glucopyranoside (astragalin) and isorhamnetin 3‐O‐β‐D ‐glucopyranoside based on FAB‐MS and NMR analyses. Assays of DPPH (1,1‐diphenyl‐β‐picryl hydrazyl) and hydroxyl radical scavenging, inhibition of linoleic acid peroxidation, and soybean lipoxygenase (LO) and hyaluronidase (HYA) inhibition were used to evaluate the antioxidant activity. Quercetin and its glycosides showed the highest antioxidant activity among the compounds. In the LO assay, the IC₅₀ values of quercetin, isoquercitrin and reynoutrin were 16.9, 40.1 and 32.9 µM respectively. Quercetin was the most effective among the flavonols. In the HYA assay the IC₅₀ values of quercetin, isoquercitrin and reynoutrin were 23.0, 20.9 and 22.1 mM respectively. Isoquercitrin had the most potent inhibitory activity on HYA. The inhibition patterns of the flavonols on LO and HYA were elucidated as mixed types of competitive and non‐competitive inhibition according to Lineweaver–Burk plot results. Although most garlic shoots and leaves are discarded and not used at present, our results suggest that ancillary garlic parts could be utilised as functional foods or ingredients. Copyright © 2004 Society of Chemical Industry     

Assessment of antiradical potential of Calluna vulgaris (L.) Hull and its major flavonoid

BACKGROUND: Antioxidant capacity of the chloroform, ethyl acetate, n‐butanol and water fractions of the aerial parts of Calluna vulgaris (L.) Hull (Ericaceae) has been assessed in this study. Antioxidant capacity of the plant was screened by assays of 2,2‐diphenyl‐β‐picrylhydrazyl, superoxide anion and hydrogen peroxide scavenging, metal‐chelating activity and reducing power. Butylated hydroxyanisole was used as reference in all assays; ethylene diamine tetraacetic acid was also used as reference in the assay of metal‐chelating activity. Total phenolic contents of the fractions were determined by the Folin–Ciocalteu method. RESULTS: Liquid chromatography/diode array detection/mass spectrometry was used for phytochemical identification of the fractions. Kaempferol‐3‐O‐β‐D ‐galactoside was found to be the major constituent in the ethyl acetate fraction (37.1 ± 0.9%), followed by the n‐butanol fraction (4.6 ± 0.1%). High occurrence of antioxidant capacity, with the exception of metal‐chelating activity, was observed in the ethyl acetate and chloroform fractions as well as in kaempferol‐3‐O‐β‐D ‐galactoside. CONCLUSION: Calluna vulgaris and its major flavonoid, kaempferol‐3‐O‐β‐D ‐galactoside, show high antioxidant capacity in various assays. As far as is known, this is the first report on antioxidant capacity of C. vulgaris and its major flavonoid. Copyright © 2009 Society of Chemical Industry     

Two Kaempferol Glycosides Separated from Camellia Oleifera Meal by High‐Speed Countercurrent Chromatography and Their Possible Application for Antioxidation

Recently, kaempferol and its glycosides have attracted considerable attention owing to their potentially health‐benefitting properties including protection against chronic diseases. Here, a microwave‐assisted extraction (MAE) method was developed for the extraction of total flavonoid glycosides (FG) from Camellia oleifera meal, a major agrifood waste largely generated as a byproduct from the Camellia oil processing industry. Compared with traditional extraction methods, MAE enables more efficient extraction of FG. High‐speed countercurrent chromatography was then applied to separate FG from MAE extract, and two major compounds were successfully separated with purities above 90.0% as determined by HPLC. These two compounds were further identified by UV, FT‐IR, ESI‐MS, ¹H‐NMR, and ¹³C‐NMR as kaempferol 3‐O‐[α‐L‐rhamnopyranosyl‐(1→6)‐β‐D‐glucopyranosyl]‐7‐O‐β‐D‐glucopyranoside and kaempferol 3‐O‐[β‐D‐glucopyranosyl‐(1→4)‐α‐L‐rhamnopyranosyl]‐7‐O‐α‐L‐rhamnopyranoside, which were for the first time separated from C. oleifera meal. The results of antioxidant activity assay demonstrated that both compounds had excellent scavenging activity for DPPH radical, and exhibited protective effects against H₂O₂‐induced oxidative damage of vascular endothelial cells. The findings of this work suggest the possibility of employing C. oleifera meal as an attractive source of health‐promoting compounds, and at the same time facilitate its high‐value reuse and reduction of environmental burden.     

Antioxidative Potential of the Polyphenolics of Stephania japonica var. Discolor (Blume) Forman: A Chromatographic (High-Performance Liquid Chromatography) and Spectrophotometric Measure

This study investigated the quantitative phytochemical contents, total phenolics, total flavonoids, total carotenoids, antioxidative capacity, tannin, proanthocyanidins, lycopene, chlorophyll a, and chlorophyll b of the Stephania japonica extract. Comprehensive antioxidative effects of the extract were also investigated. Quantitative assays were conducted through both spectrophotometric and high-performance liquid chromatographic methods. Antioxidative effects were measured through FeCl₃ reducing power, metal chelating power, reducing power, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) scavenging activity, N, N-dimethyl-1,4-diaminobenzene free radical scavenging activity, superoxide radical scavenging activity, and nitric oxide scavenging effect. The contents of total phenolics, total flavonoids, total carotenoids, total antioxidative capacity, tannin, proanthocyanidins, lycopene, chlorophyll a, and chlorophyll b were found to be 47.32 ± 0.75 mg tannic acid equivalent, 61.41 ± 1.58 mg catechin equivalent, 63.29 ± 2.21 mg, 22.85 ± 0.70 mg ascorbic acid equivalent, 76.17 ± 0.97 mg tannic acid equivalent, 94.96 ± 4.49 mg catechin equivalent, 22.19 ± 0.79 µg, 22.19 ± 0.79 µg, 7.52 ± 1.24 mg, and 10.43 ± 2.11 mg, respectively, in 1 g of ethanol extract. A high concentration of epicatechin, p-coumaric acid, and rutin hydrate and moderate concentration of caffeic acid and quercetin was detected in the extract. The IC₅₀ value for ferric reducing power assay, metal chelating assay, reducing power assay, ABTS scavenging assay, N, N-dimethyl-1,4-diaminobenzene scavenging assay, superoxide scavenging assay and nitric oxide (NO) assay were 465.06 ± 7.32 µmol ascorbic acid/g, 1656.52, 270.55, 457.27, 632.74, 217.5, and 464.00 µg/mL, respectively. No beta carotene was detected in the extract. The extract was demonstrated to be a very potential source of antioxidative metabolites.     

Phenolic acid composition and antioxidant properties of Malaysian honeys

Abstract: The phenolic acid and flavonoid contents of Malaysian Tualang, Gelam, and Borneo tropical honeys were compared to those of Manuka honey. Ferric reducing/antioxidant power assay (FRAP) and the 1,1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) radical‐scavenging activities were also quantified. All honey extracts exhibited high phenolic contents (15.21 ± 0.51– 42.23 ± 0.64 mg/kg), flavonoid contents (11.52 ± 0.27– 25.31 ± 0.37 mg/kg), FRAP values (892.15 ± 4.97– 363.38 ± 10.57 μM Fe[II]/kg), and high IC₅₀ of DPPH radical‐scavenging activities (5.24 ± 0.40– 17.51 ± 0.51 mg/mL). Total of 6 phenolic acids (gallic, syringic, benzoic, trans‐cinnamic, p‐coumaric, and caffeic acids) and 5 flavonoids (catechin, kaempferol, naringenin, luteolin, and apigenin) were identified. Among the Malaysian honey samples, Tualang honey had the highest contents of phenolics, and flavonoids, and DPPH radical‐scavenging activities. We conclude that among Malaysian honey samples, Tualang honey is the richest in phenolic acids, and flavonoid compounds, which have strong free radical‐scavenging activities.     

Pomological features, nutritional quality, polyphenol content analysis, and antioxidant properties of domesticated and 3 wild ecotype forms of raspberries (Rubus idaeus L.)

Abstract: The raspberry (Rubus idaeus L.) is an economically important berry crop that contains many phenolic compounds with potential health benefits. In this study, important pomological features, including nutrient content and antioxidant properties, of a domesticated and 3 wild (Yayla, Yavuzlar, and Yedigöl) raspberry fruits were evaluated. Also, the amount of total phenolics and flavonoids in lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits were calculated as gallic acid equivalents (GAEs) and quercetin equivalents (QE). The highest phenolic compounds were found in wild Yayla ecotype (26.66 ± 3.26 GAE/mg extract). Whilst, the highest flavonoids were determined in wild Yedigöl ecotype (6.09 ± 1.21 QA/mg extract). The antioxidant activity of lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits were investigated as trolox equivalents using different in vitro assays including DPPH^?, ABTS^?+, DMPD^?+, and O^??₂ radical scavenging activities, H₂O₂ scavenging activity, ferric (Fe³⁺) and cupric ions (Cu²⁺) reducing abilities, ferrous ions (Fe²⁺) chelating activity. In addition, quantitative amounts of caffeic acid, ferulic acid, syringic acid, ellagic acid, quercetin, α‐tocopherol, pyrogallol, p‐hydroxybenzoic acid, vanillin, p‐coumaric acid, gallic acid, and ascorbic acid in lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits were detected by high‐performance liquid chromatography and tandem mass spectrometry (LC‐MS‐MS). The results clearly show that p‐coumaric acid is the main phenolic acid responsible for the antioxidant and radical scavenging activity of lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits.     

Comprehensive determination of nine polyphenols in Polygoni Avicularis Herba with a new HPLC–DAD method and their correlation with the antioxidant activities

A simple high performance liquid chromatography (HPLC) method was established for identification and quantification of nine polyphenols (gallic acid, chlorogenic acid, caffeic acid, myricetrin, hyperoside, luteoloside, quercitrin-3-rhamnoside, quercetin and kaempferol) in Polygoni Avicularis Herba. The analysis was performed on a Pinnacle II C₁₈ column (250?×?4.6 mm, 5.0 µm) with a gradient elution of an aqueous mobile phase (containing 0.3% acetic acid) modified by acetonitrile. Diode-array detector (DAD) was used to detect the analytes at four wavelengths (270, 326, 355, and 370 nm). The established method was validated with good linearity, precision, accuracy and reproducibility to determine the polyphenols in Polygoni Avicularis Herba. The applicability of this analytical method was confirmed by successful analysis of the herb samples. The results indicated that the contents of these polyphenols varied with different locations of the samples. The anti-oxidation activities of Polygoni Avicularis Herba were further evaluated based on DPPH, ABTS and superoxide anion free radical scavenging assay. The herb exhibited obvious radical scavenging capacity, and gallic acid, chlorogenic acid, myricetrin and hyperoside played important roles in this activity.     

Chemical and antioxidative assessment of dietary turnip (Brassica rapa var. rapa L.)

The phenolic compounds and organic acids of turnip (Brassica rapa var. rapa L.) edible parts (leaves and stems, flower buds and roots) were determined by HPLC–DAD and HPLC–UV, respectively. The results revealed a profile composed of 14 phenolics (3-p-coumaroylquinic, caffeic, ferulic and sinapic acids, kaempferol 3-O-sophoroside-7-O-glucoside, kaempferol 3-O-sophoroside-7-O-sophoroside, kaempferol 3-O-(feruloyl/caffeoyl)-sophoroside-7-O-glucoside, kaempferol 3,7-O-diglucoside, isorhamnetin 3,7-O-diglucoside, kaempferol 3-O-sophoroside, 1,2-disinapoylgentiobiose, 1,2′-disinapoyl-2-feruloylgentiobiose, kaempferol 3-O-glucoside and isorhamnetin 3-O-glucoside) and six organic acids (aconitic, citric, ketoglutaric, malic, shikimic and fumaric acids). The quantification of the identified compounds showed kaempferol 3-O-sophoroside-7-O-glucoside, kaempferol 3-O-(feruloyl/caffeoyl)-sophoroside-7-O-glucoside, isorhamnetin 3,7-O-diglucoside and isorhamnetin 3-O-glucoside as the main phenolics, and malic acid as the organic acid present in highest amounts. A screening of the antioxidative potential was also performed by means of the DPPH radical scavenging assay. Turnip flower buds exhibited the strongest antioxidant capacity.     

Characteristics of the leaf parts of some traditional Korean salad plants used for food

BACKGROUND: Total phenolics content, antioxidant activity and cytotoxicity of the methanol extracts from leaf parts of 13 Korean traditional salad plants were investigated in order to determine their properties. RESULTS: The highest phenolics content (mg ferulic acid equivalents kg^?1 dry weight (d.w.), omit one) was found in methanol extracts from Polygonum aviculare, at 293.7 ± 6.0, followed by Euonymus alatus, at 250.7 ± 3.3, Saxifraga stolonifera, at 125.0 ± 8.1 and Ligularia fischeri, at 122.5 ± 5.9. The methanol plant extracts dose‐dependently increased free radical scavenging activity. Methanol extracts of Polygonum aviculare, Euonymus alatus and Saxifraga stolonifera, at 31 mg kg^?1, exhibited the highest 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging activity (%) by 90.8 ± 4.2, 85.7 ± 3.9 and 64.1 ± 3.2, respectively. According to 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay, the methanol extracts from Portulaca oleracea (IC₅₀ < 25.0 µg mL^?1) showed the highest cytotoxicity against Calu‐6, followed by Plantago asiatica (49.2 µg mL^?1) and Osmunda japonica (89.6 µg mL^?1). CONCLUSION: Total phenolics content of the tested plant extracts was correlated with the DPPH radical scavenging activity, suggesting the phenolics compounds are contributing to the antioxidant properties of Korean salad plants. The leaf parts of the 13 Korean traditional salad plants described here that are currently used as foods may also provide some benefit to human health, and research into their potential benefits as preventative and/or therapeutic agents is warranted. Copyright © 2008 Society of Chemical Industry     

Isolation of a free radical‐scavenging antioxidant from water spinach (Ipomoea aquatica Forsk)

Ipomoea aquatica Forsk, a green leafy vegetable that is a rich source of vitamins and amino acids with many health benefits, has been explored for the isolation and identification of its bioactive compounds. Activity‐guided repeated fractionation of a methanol extract on a silica gel column followed by an XAD column yielded a compound that exhibited antioxidant activity with an EC₅₀ value of 83 ± 1.02 µg ml^?1 reaction mixture. It also showed very strong lipid peroxidation‐inhibitory activity in a liposome model system with an EC₅₀ value of 72.2 ± 0.9 µg ml^?1. However, it showed negligible metal‐chelating activity. Based on UV, 2D nuclear magnetic resonance and gas chromatography/mass spectrometry studies, the compound was tentatively identified to be 7‐O‐β‐D ‐glucopyranosyl‐dihydroquercetin‐3‐O‐α‐D ‐glucopyranoside. This is the first report on the antioxidant properties of I aquatica leaf extracts. Copyright © 2005 Society of Chemical Industry     

Chemical composition and in vitro antioxidant studies on Syzygium cumini fruit

Syzygium cumini, widely known as Jamun, is a tropical tree that yields purple ovoid fleshy fruit. Its seed has traditionally been used in India for the treatment of diabetes. Based on the available ethno‐pharmacological knowledge, further studies were extended to understand the chemical composition and antioxidant activities of three anatomically distinct parts of fruit: the pulp, kernel and seed coat. Fruit parts, their corresponding ethanol extracts and residues were evaluated for chemical composition. The alcoholic extract was evaluated for its antioxidant potential against DPPH^?, OH^?, O₂^?? and lipid peroxidation. The whole fruit consisted of 666.0 ± 111.0 g kg^?1 pulp, 290.0 ± 40.0 g kg^?1 kernel and 50.0 ± 15.0 g kg^?1 seed coat. Fresh pulp was rich in carbohydrates, protein and minerals. Total fatty matter was not significant in all three parts of fruit. Detailed mineral analysis showed calcium was abundant in all fruit parts and extracts. Total phenolics, anthocyanins and flavonoid contents of pulp were 3.9 ± 0.5, 1.34 ± 0.2 and 0.07 ± 0.04 g kg^?1, respectively. Kernel and seed coat contained 9.0 ± 0.7 and 8.1 ± 0.8 g kg^?1 total phenolics respectively. Jamun pulp ethanol extract (PEE), kernel ethanol extract (KEE) and seed coat ethanol extract (SCEE) showed a high degree of phenolic enrichment. DPPH radical scavenging activity of the samples and standards in descending order was: gallic acid > quercetin > Trolox > KEE > BHT > SCEE > PEE. Superoxide radical scavenging activity (IC₅₀) of KEE was six times higher (85.0 ± 5.0 µg mL^?1) compared to Trolox (540.0 ± 5.0 µg mL^?1) and three times compared to catechin (296.0 ± 11.0 µg mL^?1). Hydroxyl radical scavenging activity (IC₅₀) of KEE was 151.0 ± 5.0 µg mL^?1 which was comparable with catechin (188.0 ± 6.0 µg mL^?1). Inhibition of lipid peroxidation of the extracts was also studied and their activity against peroxide radicals were lower than that of standard compounds (BHT, 79.0 ± 4.0 µg mL^?1; quercetin, 166.0 ± 13.0 µg mL^?1; Trolox, 175.0 ± 4.0 µg mL^?1; PEE, 342.0 ± 17.0 µg mL^?1; KEE, 202.0 ± 13.0 µg mL^?1 and SCEE, 268.0 ± 13.0 µg mL^?1. Copyright © 2007 Society of Chemical Industry     

The in vitro antioxidant and antimicrobial activities of the essential oil and various extracts of Origanum syriacum L var bevanii

The present work examines the in vitro antioxidant and antimicrobial properties of the essential oil and various extracts from the herbal parts of Origanum syriacum L var bevanii. Polar subfractions of methanol extracts from both deodorised and non‐deodorised materials showed the highest DPPH (2,2‐diphenyl‐l‐picrylhydrazyl) radical‐scavenging activity, with IC₅₀ values of 21.40 and 26.98 µg ml^?1 respectively, whereas the IC₅₀ of the essential oil was 134.00 µg ml^?1. The antioxidant potential of the extracts appeared to be closely related to the presence of polar phenolics. However, the inhibitive effect on linoleic acid oxidation might be promoted by the presence of non‐polar phenolics, as both hexane and dichloromethane extracts showed high antioxidant activities. The antimicrobial activity of the essential oil was superior to those of the other extracts. Nineteen compounds representing 962 g kg^?1 of the essential oil were identified; carvacrol (669 g kg^?1) was the main component. Overall, the results suggest that the essential oil and extracts from the herbal parts of O syriacum could be used as natural preservative ingredients in the food industry. Copyright © 2004 Society of Chemical Industry     

Identification of Bioactive Candidate Compounds Responsible for Oxidative Challenge from Hydro‐Ethanolic Extract of Moringa oleifera Leaves

Free radicals trigger chain reaction and inflict damage to the cells and its components, which in turn ultimately interrupts their biological activities. To prevent free radical damage, together with an endogenous antioxidant system, an exogenous supply of antioxidant components to the body in the form of functional food or nutritional diet helps undeniably. Research conducted by the Natl. Inst. of Health claimed that Moringa oleifera Lam possess the highest antioxidant content among various natural food sources based on an oxygen radical absorbent capacity assay. In this study, a 90% (ethanol:distilled water—90:10) gradient solvent was identified as one of the best gradient solvents for the effectual extraction of bioactive components from M. oleifera leaves. This finding was confirmed by various antioxidant assays, including radical scavenging activity (that is, 1, 1‐diphenyl‐2‐picrylhydrazyl, H₂O₂, and NO radical scavenging assay) and total antioxidant capacity (that is, ferric reducing antioxidant power and molybdenum assay). High‐performance liquid chromatography (HPLC) fingerprints of the 90% gradient extract visually showed few specific peaks, which on further analysis, using HPLC–DAD–ESI–MS, were identified as flavonoids and their derivatives. Despite commonly reported flavonoids, that is, kaempferol and quercetin, we report here for the 1st time the presence of multiflorin‐B and apigenin in M. oleifera leaves. These findings might help researchers to further scrutinize this high activity exhibiting gradient extract and its bio‐active candidates for fruitful clinical/translational investigations.     

In vitro antioxidant activity of different cultivars of banana flower (Musa paradicicus L.) extracts available in India

Abstract: Six different cultivars of banana flowers (Musa paradicicus) (Kathali, Bichi, Shingapuri, Kacha, Champa, and Kalabou) were analyzed for the content of polyphenol expressed as gallic acid equivalent and flavonoid expressed as quercetein equivalent, and the in vitro total antioxidative activities of the flower extracts were compared with standard and expressed as trolox equivalent. The reducing power, 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and 2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radical cation (ABTS?⁺) scavenging activities, inhibition of lipid peroxidation in a linoleic acid emulsion system, and liposome peroxidation system were measured and compared with respective standard antioxidants. Iron‐mediated Fenton reaction was carried out to evaluate the protective effect of the extract of banana flower (Kacha cultivar) against H₂O₂‐induced DNA damage. The Kacha variety contains the maximum amount of polyphenol (11.94 ± 0.03 mg of gallic acid equivalent/g of dry weight) and flavonoid (0.174 ± 0.001 g of quercetin equivalent/g of polyphenol). It also has the highest total antioxidant capacity, DPPH radical scavenging activity, and ABTS?⁺ radical scavenging activity with a least EC₅₀ value of 0.051 mg/mL. Hepatic cell damage in iron‐mediated Fenton reaction caused by free radicals is reduced by the banana flower extract. On the basis of the results obtained, the banana flowers are found to be a potential source of natural antioxidants. This is the first report on the antioxidant properties of the extracts from banana flowers. The study suggests that the flowers of M. paradicicus that are found in India and consumed as vegetable can provide valuable functional ingredients that help in the prevention of oxidative stress.     

Free‐radical scavenging activity of wormwood (Artemisia absinthium L) extracts

In an effort to discover new antioxidant natural compounds, wormwood (Artemisia absinthium L) an aromatic‐bitter herb, was screened. The sequential extraction was realized with five solvents of different polarities (70% methanol, petroleum ether, chloroform, ethyl acetate, n‐butanol). The antioxidative activity was tested by measuring their ability to scavenge stable 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free radical and reactive hydroxyl radical during the Fenton reaction trapped by 5,5‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO), using electron spin resonance (ESR) spectroscopy. Results demonstrated that the antiradical and antioxidative activity depend on the type and concentration of applied extracts and increased in the order ethyl acetate > methanol > n‐butanol > chloroform > petroleum ether > remaining water extracts. The investigation showed that the antiradical activity increased with increasing concentration of all extracts. The high contents of total phenolic compounds (25.6 mg g^?1) and total flavonoids (13.06 mg g^?1) indicated that these compounds contribute to the antiradical and antioxidative activity. In a model system, the formation of o‐semiquinone radicals from quercetin and chlorogenic acid was obtained to prove the mechanism (hydrogen donating and/or one‐electron reduction) of free‐radical scavenging activity. Copyright © 2004 Society of Chemical Industry     

Phenolic Compounds and Antioxidant Capacities of 10 Common Edible Flowers from China

The free and bound phenolic compounds in 10 common Chinese edible flowers were investigated using reversed phase high‐performance liquid chromatography. Their antioxidant capacities were evaluated using 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical‐scavenging activity, 2,2'‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid) (ABTS) radical‐scavenging activity, oxygen radical absorption capacity (ORAC), ferric reducing antioxidant power (FRAP), and cellular antioxidant activity (CAA). Free factions were more prominent in phenolic content and antioxidant capacity than bound fractions. Paeonia suffruticosa and Flos lonicerae showed the highest total phenolic content (TPC) 235.5 mg chlorogenic acid equivalents/g of dry weight and total flavonoid content 89.38 mg rutin equivalents/g of dry weight. The major phenolic compounds identified were gallic acid, chlorogenic acid, and rutin. P. suffruticosa had the highest antioxidant capacity in the DPPH, ABTS, and ORAC assays, which were 1028, 2065, 990 μmol Trolox equivalents/g of dry weight, respectively, whereas Rosa chinensis had the highest FRAP value (2645 μmol Fe²⁺ equivalents /g of dry weight). The P. suffruticosa soluble phenolics had the highest CAA, with the median effective dose (EC₅₀) 26.7 and 153 μmol quercetin equivalents/100 g of dry weight in the phosphate buffered saline (PBS) and no PBS wash protocol, respectively. TPC was strongly correlated with antioxidant capacity (R = 0.8443 to 0.9978, P < 0.01), which indicated that phenolics were the major contributors to the antioxidant activity of the selected edible flowers.     

Antioxidative principals of Jussiaea repens: an edible medicinal plant

Jussiaea repens L. (JRL) is an edible medicinal plant and is also used as a vegetable by the local people in southwestern China. The crude extract and its four fractions derived from JRL were evaluated for the 1,1‐diphenyl‐2‐picrylhydrazyl radical‐scavenging ability, hydroxyl radical‐scavenging capacity and the potassium ferricyanide reduction property. The ethyl acetate‐soluble fraction (EAF) and EAF6 (a subfraction derived from EAF) were the most valuable fraction and subfraction, respectively. Furthermore, bioactivity‐guided chromatographic fractionation revealed that three pure compounds greatly contributed to the antioxidant activities. Qualitative and quantitative analyses of the major antioxidant constituents in the extract were systematically conducted by NMR, mass spectral analyses and RP‐HPLC. The result demonstrated that rosmarinic acid (2.00 mg g^?1 JRL dry weight) quercetin 3‐O‐β‐d ‐glucopyranoside (9.88 mg g^?1 JRL dry weight), and kaempferol 3‐O‐β‐d ‐glucopyranoside (1.85 mg g^?1 JRL dry weight) were the major antioxidative constituents in JRL. These compounds are reported for the first time from this plant.     

Change in Flavonoid Composition and Antioxidative Activity during Fermentation of Onion (Allium cepa L.) by Leuconostoc mesenteroides with Different Salt Concentrations

The aim of this study is to investigate the change in flavonoid composition and antioxidative activity during fermentation of onion (Allium cepa L.) by Leuconostoc mesenteroides with different NaCl concentrations. In order to qualify and quantify the flavonoids during fermentation of onion, 7 flavonoids, [quercetin 3,7‐O‐β‐d ‐diglucopyranoside (Q3,7G), quercetin 3,4′‐O‐β‐d ‐diglucopyranoside (Q3,4′G), quercetin 3‐O‐β‐d ‐glucopyranoside (Q3G), quercetin 4′‐O‐β‐d ‐glucopyranoside (Q4′G), isorhamnetin 3‐O‐β‐d ‐glucopyranoside (IR3G), quercetin (Q), and isorhamnetin (IR)], were isolated and identified from onion. During fermentation, the contents of flavonoid glucosides (Q3,7G, Q3,4′G, Q3G, Q4′G, and IR3G) gradually decreased, whereas the contents of flavonoid aglycones (Q, IR) gradually increased. Decline rates of the flavonoid glucosides increased with the addition of L. mesenteroides. Furthermore, the activity of β‐glucosidase, which is produced by L. mesenteroides, is dose‐dependently inhibited with different NaCl concentrations during fermentation. The presence of L. mesenteroides enhanced the antioxidative activity of onion as demonstrated using the 1,1‐diphenyl‐2‐picrylhydrazyl, 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid), and reducing power assays. The enhancement of antioxidative activity was considered because the content of flavonoid aglycones increased during fermentation. However, the addition of NaCl may decrease the antioxidative activity; we surmise that this phenomenon occurs because of the inhibition of β‐glucosidase by NaCl. Therefore, we conclude that the addition of NaCl may be useful for the regulation of antioxidative activity via the control of β‐glucosidase action, during the fermentation of flavonoid glucoside‐rich foods.     

Antioxidant and semicarbazide‐sensitive amine oxidase inhibitory activities of alginic acid hydroxamates

The commercial polysaccharides of alginic acid (medium (3500 cps, 2% solution) and low (250 cps, 2% solution) viscosities) were esterified with acidic methanol (1 mmol L^?1 HCl) at 4 °C with gentle stirring for 5 days to obtain methyl esters of medium‐viscosity alginic acid (ME‐MVA) and low‐viscosity alginic acid (ME‐LVA). These ME‐MVA and ME‐LVA were reacted with alkaline hydroxylamine to obtain medium‐viscosity alginic acid hydroxamates (MVA‐NHOH) and LVA‐NHOH. The percentages of hydroxamic acid content in MVA‐NHOH and LVA‐NHOH were calculated as 25% and 20%, respectively. The hydroxamate derivatives of alginic acid were used to test the antioxidant and semicarbazide‐sensitive amine oxidase (SSAO) inhibitory activities in comparison with original materials (MVA and LVA). The half‐inhibition concentrations, IC₅₀, of scavenging activity against 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) were 24.5 and 29.8 µg mL^?1 for MVA‐NHOH and LVA‐NHOH, respectively. However, few scavenging activities of the MVA and LVA were found at the same concentrations. The IC₅₀ of the positive control of butylated hydroxytoluene was 5 µg mL^?1. The scavenging activity of DPPH radical was pH‐dependent, and the optimal pH for both of MVA‐NHOH and LVA‐NHOH was the Tris‐HCl buffer (pH 7.9). Using electron spin resonance (ESR) to detect the activity of scavenging hydroxyl radicals, both alginic acid hydroxamates showed dose‐dependent scavenging activities, and the IC₅₀ was 90 and 92 µg mL^?1, respectively, for MVA‐NHOH and LVA‐NHOH. Both alginic acid hydroxamates also exhibited protection against hydroxyl radical‐mediated DNA damage. Both MVA‐NHOH and LVA‐NHOH showed dose‐dependent inhibitory activities against bovine SSAO (2.53 units); the IC₅₀ was 0.16 and 0.09 µg mL^?1, respectively, for MVA‐NHOH and LVA‐NHOH, compared with 3.81 µg mL^?1 of semicarbazide (positive controls). Amine oxidase activity staining also revealed that both MVA‐NHOH and LVA‐NHOH exhibited SSAO inhibitory activities. Both MVA‐NHOH and LVA‐NHOH showed mixed non‐competitive inhibition against bovine SSAO. It was found that the V′_max value was reduced and the K′_m value was either increased (added MVA‐NHOH, 0.05 µg mL^?1) or reduced (added LVA‐NHOH, 0.11 µg mL^?1) in the presence of alginic acid hydroxamate. Copyright © 2006 Society of Chemical Industry