Vialinin A, a novel 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenger from an edible mushroom in China

While screening for bioactive compounds from edible mushrooms, a new potent antioxidant, vialinin A (1), together with a known compound, ganbajunin B (2), and a mixture of ganbajunins D (3) and E (4), were isolated from the dry fruiting bodies of Thelephora vialis. The structure of 1, 5',6'-bis(phenylacetoxy)-1,1':4',1'-terphenyl-2',3',4,4'-tetraol, was elucidated by spectroscopic and chemical methods. This compound had strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging activity with an EC(50) value of 14.0 microM, nearly equal to that of butylated hydroxytoluene (BHT; EC(50) = 10.0 microM). A radical scavenging experiment using 1 and DPPH radicals indicated that 1 donated two hydrogen atoms to two molecules of the DPPH radical under hydrophobic conditions.     

Antioxidant properties of natural p-terphenyl derivatives from the mushroom Thelephora ganbajun

The antioxidant activity in vitro of three poly(phenylacetyloxy)-substituted 1,1':4',1"-terphenyl compounds from the edible mushroom Thelephora ganbajun were investigated. The IC50 values of compounds 1-3 for lipid peroxidation in rat liver homogenate were 400, 48, 54 microM, respectively. Compounds 1-3 increased superoxide dismutase (SOD) activity with EC50 values of 182, 74, 204 microM. They were also assessed on the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity with EC50 values of 49, 1233, 55 microM.     

Radical-scavenging activities of new hydroxylated ursane triterpenes from cv. Annurca apples

Two new ursolic acid triterpene derivatives, compounds 2 and 3, have been isolated from cv. Annurca apple fruit, a high-quality apple variety widely cultivated in southern Italy, together with the known 2-oxopomolic acid (1). The new compounds were identified by means of different spectroscopic techniques as 3-epi-2-oxopomolic acid (= (3alpha)-3,19-dihydroxy-2-oxours-12-en-28-oic acid; 2) and (1alpha)-1-hydroxy-3-oxours-12-en-28-oic acid (3). Compounds 1-3 were tested for their radical-scavenging activities with the aid of a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay (Fig. 2). All three constituents showed activities similar to that of the reference antioxidant alpha-tocopherol (vitamin E).     

Microwave-assisted synthesis of 4'-azaflavones and their N-alkyl derivatives with biological activities

4'-Azaflavone (=2-(pyridin-4-yl)-4H-1-benzopyran-4-one; 4) and 3-[(pyridin-4-yl)methyl]-4'-azaflavone (5) were synthesized by a simple environmentally friendly microwave-assisted one-pot method through the cyclization of 3-hydroxy-1-(2-hydroxyphenyl)-3-(pyridin-4-yl)propan-1-one (1), (E)-2'-hydroxy-4-azachalcone (2; chalcone=1,3-diphenylprop-2-en-1-one), and 2'-hydroxy-2-[(hydroxy)(pyridin-4-yl)methyl]-4'-azachalcone (3) under solventless conditions using silica-supported NaHSO(4), followed by treatment with base. In addition, N-alkyl-substituted 4'-azaflavonium bromides 6 and 7 were prepared from compounds 4 and 5, respectively. The antimicrobial and antioxidant activities of compounds 1-7 were tested. The N-alkyl-substituted 4'-azaflavonium bromides 6 and 7 showed high antimicrobial activity against the Gram-positive bacteria and the fungus tested, with MIC values close to those of reference antimicrobials ampicilline and fluconazole. The alkylated compounds 6 and 7 also showed a good antioxidant character in the two antioxidant methods, DPPH (=1,1-diphenyl-2-picrylhydrazyl) radical-scavenging and ferric reducing/antioxidant power (FRAP) tests.     

Phenolic antioxidants from the whole plant of Phyllanthus urinaria

The 1,1-diphenyl-2-picrydydrazyl (DPPH) assay on the extract of Phyllanthus urinaria L. (Euphorbiaceae) displayed considerable radical-scavenging activity (SC50 = 14.3 microg/ml). Further bioassay-guided purification of the extract led to the isolation of a series of 15 phenolic compounds, including the ellagitannins 1-7, the flavonoids 8-10, and the simple hydroxylated (or glycosylated) aromatic acids 11-15. Their structures were identified by spectroscopic analyses and comparison with authentic samples or literature data. The structure of repandinin B (1) was for the first time fully assigned by 1D- and 2D-NMR experiments. The phenolic compounds 1, 3, 4, 6, 9, 11, and 15 have not been isolated before from the title plant. The antioxidant activities and mushroom-tyrosinase-inhibitory activities of all compounds were determined by DPPH-radical-scavenging and mushroom-tyrosinase-inhibitory assays (Table 2).     

Antioxidant activity of L-adrenaline: a structure-activity insight

L-adrenaline belongs to a group of the compounds known as catecholamines, which play an important role in the regulation of physiological process in living organisms. The antioxidant activity and antioxidant mechanism of L-adrenaline was clarified using various in vitro antioxidant assays including 1,1-diphenyl-2-picryl-hydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), N,N-dimethyl-p-phenylenediamine (DMPD(+)), and superoxide anion radicals (O(2)(-)) scavenging activity, hydrogen peroxide (H(2)O(2)), total antioxidant activity, ferric ions (Fe(3+)) and cupric ions (Cu(2+)) reducing ability, ferrous ions (Fe(2+)) chelating activity. L-adrenaline inhibited 74.2% lipid peroxidation of a linoleic acid emulsion at 30 microg/mL concentration. On the other hand, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), alpha-tocopherol and trolox displayed 83.3, 82.1, 68.1 and 81.3% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. BHA, BHT, alpha-tocopherol and trolox were used as reference antioxidants and radical scavenger compounds. Moreover, this study will bring an innovation for further studies related to antioxidant properties of L-adrenaline. According to present study, L-adrenaline had effective in vitro antioxidant and radical scavenging activity.     

Comparison of in vitro antioxidant and antiradical activities of L-tyrosine and L-Dopa

Summary. Phenolic compounds are interesting because of their antioxidant properties. In the present study, the antioxidant properties of L-tyrosine as a monophenolic and L-Dopa as a diphenolic amino acid were investigated by using different antioxidant assays: (i) 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH^•) scavenging; (ii) 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation decolorization assay; (iii) total antioxidant activity by ferric thiocyanate method; (iv) ferric ions (Fe³⁺) reducing power; (v) superoxide anion radical (O₂ ^•−) scavenging; (vi) hydrogen peroxide (H₂O₂) scavenging, and (vii) ferrous ions (Fe²⁺) chelating activities. Butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol and trolox, a water-soluble analogue of tocopherol, were used as the reference antioxidant compounds. At the same concentration (20 μg/mL), L-tyrosine and L-Dopa showed 30.6 and 67.9% inhibition of lipid peroxidation of linoleic acid emulsion, respectively. On the other hand, BHA, BHT, α-tocopherol and trolox indicated inhibitions of 74.4, 71.2, 54.7 and 20.1% on the peroxidation of linoleic acid emulsion, respectively, at the above-mentioned concentration. In addition, L-tyrosine and L-Dopa had an effect on DPPH radical scavenging, ABTS radical scavenging, superoxide anion radical scavenging, H₂O₂ scavenging, total ferric ions reducing power and metal chelating on ferrous ions activities.     

DPPH radical-scavenging compounds from dou-chi, a soybean fermented food

Dou-chi, a traditional soybean food fermented with Aspergillus sp., is usually used as a seasoning in Chinese food, and has also been used as a folk medicine in China and Taiwan. As 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavengers, four phenol compounds, one isoflavanone, eight isoflavones and one 4-pyrone have been isolated from dou-chi. Among these fourteen compounds, 3'-hydroxydaidzein, dihydrodaidzein and a 4-pyrone compound have not yet been isolated from soybean miso. The structure of the novel 4-pyrone compound, 3-((E)-2-carboxyethenyl)-5-(4-hydroxyphenyl)-4-pyrone-2-carboxylic acid was elucidated by using the same compound as that obtained from the biotransformation of daidzein. 3'-Hydroxydaidzein showed as high DPPH radical-scavenging activity as that of alpha-tocopherol, and 6-hydroxydaidzein had mushroom tyrosinase inhibitory activity with an IC(50) value of 10 muM. The order of estrogenic activity is as follows: genistein > daidzein > 3'-hydroxydaidzein > 8-hydroxygenistein, using a green fluorescent protein expression system. Furthermore, the contents of isoflavones in the fermentation process of dou-chi were measured.     

Antioxidant activities of three dihydrochalcone glucosides from leaves of Lithocarpus pachyphyllus

In vitro antioxidant activities of three sweet dihydrochalcone glucosides from the leaves of Lithocarpus pachyphyllus (Kurz) Rehd. (Fagaceae), trilobatin 2"-acetate (1), phloridzin (2) and trilobatin (3), were investigated. The IC50 (50% inhibitory concentration) values for compounds 1-3 of lipid peroxidation in rat liver homogenate were 261, 28, 88 microM, respectively. Compounds 1-3 increased superoxide dismutase (SOD) activity with EC50 (50% effective concentration) values of 575, 167, 128 microM, and glutathione peroxidase (GSH-Px) activity with EC50 values of 717, 347, 129 microM, respectively, and showed only weak DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity.     

In vitro antioxidant activity of silymarin

Silymarin, a known standardized extract obtained from seeds of Silybum marianum is widely used in treatment of several diseases of varying origin. In the present paper, we clarified the antioxidant activity of silymarin by employing various in vitro antioxidant assay such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH(.)) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, total antioxidant activity determination by ferric thiocyanate, total reducing ability determination by Fe3+ - Fe2+ transformation method and Cuprac assay, superoxide anion radical scavenging by riboflavin/methionine/illuminate system, hydrogen peroxide scavenging and ferrous ions (Fe2+) chelating activities. Silymarin inhibited 82.7% lipid peroxidation of linoleic acid emulsion at 30 microg/mL concentration; butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), alpha-tocopherol and trolox indicated inhibition of 83.3, 82.1, 68.1 and 81.3% on peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, silymarin had an effective DPPH(.) scavenging, ABTS(.)+ scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power by Fe3+-Fe2+ transformation, cupric ions (Cu2+) reducing ability by Cuprac method, and ferrous ions (Fe2+) chelating activities. Also, BHA, BHT, alpha-tocopherol and trolox, were used as the reference antioxidant and radical scavenger compounds. Moreover, this study, which clarifies antioxidant mechanism of silymarin, brings new information on the antioxidant properties of silymarin. According to the present study, silymarin had effective in vitro antioxidant and radical scavenging activity. It could be used in the pharmacological and food industry because of its antioxidant properties.     

Antioxidant and radical scavenging properties of curcumin

Curcumin (diferuoyl methane) is a phenolic compound and a major component of Curcuma longa L. In the present paper, we determined the antioxidant activity of curcumin by employing various in vitro antioxidant assays such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH*) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, N,N-dimethyl-p-phenylenediamine dihydrochloride (DMPD) radical scavenging activity, total antioxidant activity determination by ferric thiocyanate, total reducing ability determination by the Fe(3+)-Fe(2+) transformation method, superoxide anion radical scavenging by the riboflavin/methionine/illuminate system, hydrogen peroxide scavenging and ferrous ions (Fe(2+)) chelating activities. Curcumin inhibited 97.3% lipid peroxidation of linoleic acid emulsion at 15 microg/mL concentration (20 mM). On the other hand, butylated hydroxyanisole (BHA, 123 mM), butylated hydroxytoluene (BHT, 102 mM), alpha-tocopherol (51 mM) and trolox (90 mM) as standard antioxidants indicated inhibition of 95.4, 99.7, 84.6 and 95.6% on peroxidation of linoleic acid emulsion at 45 microg/mL concentration, respectively. In addition, curcumin had an effective DPPH* scavenging, ABTS*(+) scavenging, DMPD*(+) scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe(3+)) reducing power and ferrous ions (Fe(2+)) chelating activities. Also, BHA, BHT, alpha-tocopherol and trolox, were used as the reference antioxidant and radical scavenger compounds. According to the present study, curcumin can be used in the pharmacological and food industry because of these properties.     

Screening of antiradical and antioxidant activity of monodesmosides and crude extract from Leontice smirnowii tuber.

Leontice smirnowii is a member of the Berberidaceae family. In the current study we investigated the possible antiradical and antioxidant activity of the monodesmosides (MLS) and crude extract (CELS) of Leontice smirnowii using different antioxidant tests: 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging, scavenging of superoxide anion radical-generated non-enzymatic system, ferric thiocyanate (FTC) method, reducing power, hydrogen peroxide scavenging and metal chelating activities. Experiment revealed that MLS and CELS have an antioxidant effect concentration-dependently. Total antioxidant activity was performed according to FTC method. At the 30mug/ml concentration, the inhibition effects of MLS and CELS on peroxidation of linoleic acid emulsion were found to be 95.3% and 95.6%, respectively. On the other hand, percentage inhibition of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), alpha-tocopherol and trolox were found to be 98.2%, 98.5%, 84.0% and 87.9% inhibition of peroxidation of linoleic acid emulsion, respectively, at the same concentration. In addition, MLS and CELS had effective DPPH radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, reducing power and metal chelating activities. Also, these various antioxidant activities were compared with BHA, BHT, alpha-tocopherol and trolox which were accepted as references antioxidants.     

Antioxidant phenolic compounds from the stems of Entada phaseoloides

The EtOH extract of the stems of Entada phaseoloides displayed potent antioxidant activity when assessed by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging, reducing power, β-carotene-bleaching, and superoxide radical-scavenging analyses. Fractionation of the EtOH extracts showed that the AcOEt fraction is the most active, followed by the H(2) O fraction, while BuOH fraction was least active. Further activity-guided fractionation studies on the active fractions resulted in the isolation of 22 compounds. The identities of these compounds were established based on extensive spectroscopic studies. Furthermore, the antioxidant activities of the isolated compounds were evaluated by using the above-mentioned five assays. The results demonstrated that the EtOH extract of E. phaseoloides stems exhibits an excellent antioxidant activity and thus presents a great potential as a source of natural antioxidants.     

Antioxidant activity of twenty five plants from Colombian biodiversity

The antioxidant activity of the crude n-hexane, dichloromethane, and methanol extracts from 25 species belonging to the Asteraceae, Euphorbiaceae, Rubiaceae, and Solanaceae families collected at natural reserves from the Eje Cafetero Ecorregión Colombia, were evaluated by using the spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging method. The strongest antioxidant activities were showed by the methanol and dichloromethane extracts from the Euphorbiaceae, Alchornea coelophylla (IC50 41.14 mg/l) and Acalypha platyphilla (IC50 111.99 mg/l), respectively. These two species had stronger DPPH radical scavenging activities than hydroquinone (IC50 151.19 mg/l), the positive control. The potential use of Colombian flora for their antioxidant activities is discussed.     

New phenolic constituents from Balanophora polyandra with radical-scavenging activity

The 80% acetone extract of Balanophora polyandra Griff. (Balanophoraceae) was found to exhibit high radical-scavenging activity (SC(50)=14.48 mug/ml) towards 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. Further chemical investigation led the isolation of two new hydrolysable tannins, balapolyphorins A (1) and B (2), together with 20 known phenolic compounds (3-22). Their structures were established by detailed spectroscopic analysis, and the radical-scavenging properties of all isolated compounds were determined by DPPH assay.     

Antioxidant activity of phenylpropanoid esters isolated and identified from Platycodon grandiflorum A. DC

Platycodon grandiflorum A. DC (Campanulaceae) is used as a traditional oriental medicine and also as a food in Korea. Here we investigated its antioxidant activity, and isolated and identified its active compounds. Petroleum ether extracts from the whole root of P. grandiflorum were fractionated by silica gel column chromatography using a solvent gradient (petroleum ether:diethyl ether, v/v; 9:1-5:5). The 8:2 fraction showed a higher radical scavenging activity than the other fractions, and active compounds were purified from this fraction by reversed-phased HPLC. Two active compounds were identified as coniferyl alcohol esters of palmitic and oleic acids by FAB-MS, UV, IR and NMR spectroscopy. The antioxidant activities of these two compounds, which were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide and nitric oxide radical scavenging capacity, were found to be as high as those of BHT or BHA.     

Antioxidant activities of flavidin in different in vitro model systems

Flavidin was isolated from Orchidaceae species and purified by silica gel column chromatography. The structure was identified using physical and spectral ((1)H, (13)C NMR, and mass) data. Antioxidant potency of flavidin was investigated employing various established in vitro model systems viz., beta-carotene-linoleate, 1,1-diphenyl-2-picryl hydrazyl (DPPH), phosphomolybdenum method, and scavenging of hydrogen peroxide methods. Flavidin showed very good antioxidant activity (90.2%) and almost equivalent to that of BHA at 50ppm level by beta-carotene-linoleate method. Radical scavenging activity of flavidin was compared with BHA at 5, 10, 20, and 40ppm concentration and flavidin showed more radical scavenging activity than BHA at all the tested concentrations. Furthermore, flavidin showed very good antioxidant capacity by the formation of phosphomolybdenum complex method. Besides this, flavidin showed effective hydrogen peroxide scavenging activity. The data obtained in the in vitro models clearly establish the antioxidant potency of flavidin. However, comprehensive studies need to be conducted to ascertain the in vivo safety of flavidin in experimental animal models. This is the first report on antioxidant activity of 9,10-dihydro-5H-phenanthro-(4,5 bcd)-pyrans/flavidin type of compounds.     

Comparison of the relative activities of alpha-tocopherol and PMC on platelet aggregation and antioxidative activity.

In this study, PMC (2,2,5,7,8-pentamethyl-6-hydroxychromane), a potent antioxidant derived from alpha-tocopherol, dose-dependently inhibited agonist-induced platelet aggregation in human platelet-rich plasma. PMC is over 5-10 times more potent than alpha-tocopherol in inhibiting human platelet aggregation. Moreover, PMC (25-350 microM) dose-dependently reduced the relative fluorescence intensity of platelet membrane tagged with diphenylhexatriene (DPH). PMC is about 6-times more potent than alpha-tocopherol on this effect. Furthermore, antioxidative activity of PMC was investigated using two in vitro models. PMC inhibited non-enzymatic iron-induced lipid peroxidation in rat brain homogenates with an IC50 value of 0.21+/-0.05 microM. It was more potent than alpha-tocopherol or other classical antioxidants. PMC also scavenged the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). The concentration of PMC resulting in a decrease of 0.20 in the absorbance of DPPH was about 12.1+/-3.6 microM, was comparable in potency to alpha-tocopherol, butylated hydroxytoluence and Trolox. The antiplatelet activity of PMC may possibly be due initially to an increase in fluidity of the platelet membrane followed by inhibition of platelet aggregation. Our results indicate that PMC is a potentially effective antioxidant and antiaggregating agent, and could be helpful the design of compounds with more clinical effectiveness.     

Antioxidant properties of complexes of flavonoids with metal ions

The formation of complexes of metal ions with the flavonoids quercetin (L1), rutin (L2), galangin (L3) and catechin (L4) has been investigated by UV-visible spectroscopy. The antioxidant activities of the compounds were evaluated by using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicalscavenging method. In this work, we have shown that the complexed flavonoids are much more effective free radical scavengers than the free flavonoids. We suggest that the higher antioxidant activity of the complexes is due to the acquisition of additional superoxide dismutating centers. Radical scavenging activities of the compounds were also investigated from an electrochemical point of view. There is a relationship between the logarithm of the antioxidant activity (represented by EC50) and the oxidation potential. The synergic effect of the complexes and ascorbic acid were studied by [13C]-NMR analyses. The results show that ascorbic acid can protect flavonoids from oxidative degradation, and reveal antioxidant synergies between ascorbic acid and the compounds.     

Radical scavenging activities of Heracleum aquilegifolium Wight (Apiaceae) fruit oils in vitro

The fruits of Heracleum aquilegifolium Wight (Apiaceae) were collected from Western Ghats of the Indian Peninsula. The essential oils were extracted by hydrodistillation. The chemical composition of the essential oils was analysed by gas chromatography and gas chromatography-mass spectrometry (GC-MS). Beta-Pinene (22.3%), 1,8-cineole (20.3%), and beta-phellandrene (12.4%) were the main components of H. aquilegifolium fruit oils. The antioxidant properties of essential oils of H. aquilegifolium were examined by different procedures namely reducing power ability, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, nitric oxide radical scavenging activity, hydrogen peroxide scavenging activity, hydroxyl radical scavenging activity, superoxide anion scavenging activity, and metal chelating activity. The antioxidant activities were compared with those of synthetic antioxidants and standard drugs such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), ascorbic acid, alpha-tocopherol, curcumin, and quercetin. The study confirmed the possible antioxidant potential of essential oils tested with various in vitro antioxidant methods. The presence of monoterpenes in combination with other components in the oils could be responsible for the activity.