3-methylquercetin and 1-1-diphenyl-2-picrylhydrazyl

Quercetin derivatives are widespread in the plant kingdom and exhibit various biological actions. The aim of this study was to investigate the structure-activity relationships of quercetin derivatives, with a focus on the influence of functional groups and sugar composition on their antioxidant capacity. A series of quercetin derivatives were therefore prepared and assessed for their DPPH radical scavenging properties. Isoquercetin O-gallates were more potent radical scavengers than quercetin. The systematic analysis highlights the importance of the distribution of hydroxy substituents in isoquercetin O-gallates to their potency.

Topics: Antioxidants; Biphenyl Compounds; Free Radical Scavengers; Molecular Structure; Picrates; Quercetin; Structure-Activity Relationship

A small Chilean variety of pears growing in the town of Toconao, an oasis located at the northeastern edge of the Salar de Atacama, northern Chile, was studied by means of modern PDA and high resolution mass spectral data (UHPLC-PDA-HESI-orbitrap-MS/MS). In addition, the antioxidant features of the fruits were compared with the varieties Packhman's Triumph and Abate Fetel and correlated with the presence of phenolic compounds. The non-pigmented phenolics were fingerprinted and related to the antioxidant capacities measured by the bleaching of the DPPH radical, the ferric reducing antioxidant power (FRAP), the superoxide anion scavenging activity assay (SA), and total content of phenolics and flavonoids measured by spectroscopic methods. The machine allowed a fast separation of 15 min employing a flow rate of 1 mL per minute and could accurately identify 25 compounds, including several isorhamnetin derivatives and phenolic acids, present in the peel and pulps of this Chilean variety for the first time. The compounds were monitored using a wavelength range of 210-800 nm. The native small Chilean pear showed the highest antioxidant activity measured as the bleaching of the DPPH radical, the ferric reducing antioxidant power and superoxide anion scavenging activity (8.61 ± 0.65 μg/mL, 712.63 ± 12.12 micromols trolox equivalents (μmol/TE)/100 g FW, and 82.89% ± 2.52% at 100 μg/mL, respectively).

Topics: Antioxidants; Biphenyl Compounds; Chile; Chromatography, High Pressure Liquid; Desert Climate; Flavonoids; Fruit; Phenols; Picrates; Plant Extracts; Pyrus; Quercetin; Superoxides; Tandem Mass Spectrometry

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.

Topics: beta-Glucosidase; Biphenyl Compounds; Fermentation; Flavonoids; Flavonols; Food Handling; Glucosides; Humans; Leuconostoc mesenteroides; Onions; Oxidation-Reduction; Picrates; Plant Extracts; Quercetin; Sodium Chloride

An analytical study was carried out on the presence of antioxidant constituents and the in vitro antioxidant capacity in the extracts of three species of Spanish red-skinned cactus pear fruits (Opuntia ficus-indica, Opuntia undulata and Opuntia stricta). The cactus pear fruit extracts were analyzed for determined constituents: ascorbic acid, flavonoids (quercetin, isorhamnetin, myricetin, kaempferol and luteolin), betalains, taurine, total carotenoids and total phenolics. The antioxidant capacity was assessed by means of two different methods: the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (Trolox equivalent antioxidant capacity) method and the 2,2-diphenyl-1-picrylhydrazyl radical method. Opuntia ficus-indica fruit extract had the strongest antioxidant capacity and taurine content. O. stricta fruits were the richest in ascorbic acid and total phenolics, whereas O. undulata fruits showed the highest carotenoid content. Quercetin and isorhamnetin were the main flavonoids detected. This study provides basic information on the presence of bioactive compounds and antioxidant capacity in extracts of cactus pear fruits, in order to consider these extracts as ingredient for the production of health-promoting food.

Topics: Antioxidants; Ascorbic Acid; Biphenyl Compounds; Carotenoids; Chromans; Flavonoids; Flavonols; Fruit; Opuntia; Phenols; Picrates; Plant Preparations; Polyphenols; Quercetin; Taurine

In the present study, the process of separation and purification of isohamnetin from marc of sea buckthorn was obtained. The antioxidant properties of the pure isolated isorhamnetin were evaluated by the scavenging of the diphenylpicrylhydrazyl radical (DPPH), iron (III) to iron (II)-reducing, and iron-chelating assays. High purity isorhamnetin (92.1%) was obtained and the results of antioxidant assays showed that isorhamnetin performed significantly compared with ascorbic acid and BHT, and the linear correlations were good in these assays. In conclusion, isorhamnetin may have potential as a natural antioxidant to alternate synthetic substances as food additive with its antioxidant activity.

Topics: Antioxidants; Biphenyl Compounds; Flavonols; Hippophae; Iron; Picrates; Plant Extracts; Quercetin

In this study, we isolated two new isorhamnetin glycosides, designated as nelumboroside A (3) and nelumboroside B (4), as well as the previously-characterized isorhamnetin glucoside (1) and isorhamnetin rutinoside (2), from the n-BuOH fraction of Nelumbo nucifera stamens. The structures of the two new compounds were then determined, using chemical and spectroscopic techniques. All isolated isorhamnetin glycosides 1-4 showed marked antioxidant activities in the DPPH, and ONOO- assays.

Topics: Biphenyl Compounds; Flavonols; Flowers; Free Radical Scavengers; Glycosides; Hydrazines; Nelumbo; Peroxynitrous Acid; Picrates; Quercetin

The present investigation was undertaken to determine the protective effects of flavonoids from seabuckthorn (FSBT), a traditional Chinese medicine, on endothelial cell line EA.hy926 injury induced by oxidized low-density lipoprotein (ox-LDL). Possible mechanisms were then explored. The effects of quercetin and isorhamnetin, 2 major components of FSBT, were examined as well. Indices such as cell viability, lactate dehydrogenase, nitric oxide (NO), superoxide dismutase, and superoxide were measured. Reverse transcription polymerase chain reaction, Western blot, and immunocytochemistry were employed to determine the endothelial constitutive NO synthase (eNOS) and lectinlike low-density lipoprotein receptor-1 (LOX-1) expression. Cell viability decreased significantly after 24 hours treatment with ox-LDL, accompanied with apparent secretion disorders such as NO reduction and lactate dehydrogenase increase. FSBT pretreatment could remarkably prevent both cell death and secretion disorders in a concentration-dependent manner. Besides, it was observed that ox-LDL triggered superoxide production and suppressed the superoxide dismutase activity, both of which could be prevented by FSBT pretreatment. Moreover, ox-LDL inhibited eNOS expression and increased LOX-1 expression, whereas FSBT pretreatment partly abolished these effects. Similar effects were obtained with quercetin and isorhamnetin, implying that they may contribute, at least in part, to the protective effects of FSBT. The data indicate that the protective effects of FSBT against ox-LDL induced endothelial cell injuries might derive from its antioxidant activity and its capability in modulating the expression of eNOS and LOX-1. And quercetin and isorhamnetin may contribute to these effects of FSBT.

Topics: Biphenyl Compounds; Blotting, Western; Cell Line; Cell Survival; Chromatography, High Pressure Liquid; Endothelial Cells; Flavonoids; Flavonols; Free Radical Scavengers; Gene Expression; Hippophae; Humans; Hydrazines; Immunohistochemistry; L-Lactate Dehydrogenase; Lipoproteins, LDL; Nitric Oxide; Nitric Oxide Synthase Type III; Picrates; Quercetin; Reverse Transcriptase Polymerase Chain Reaction; Scavenger Receptors, Class E; Superoxide Dismutase

Hippophae rhamnoides or seabuckthorn is used extensively in Indian and Tibetan traditional medicine for the treatment of circulatory disorders, ischemic heart disease, hepatic injury, and neoplasia. In the present study, we have evaluated the radioprotective potential of REC-1001, a fraction isolated from the berries of H. rhamnoides. Chemical analysis of the extract indicated that REC-1001 was approximately 68% by weight polyphenols, and contained kaempferol, isorhamnetin, and quercetin. The effect of REC-1001 on modulating radiation-induced DNA damage was determined in murine thymocytes by measuring nonspecific nuclear DNA damage at the whole genome level using the alkaline halo assay and by measuring sequence/gene-specific DNA damage both in nuclear DNA (beta-globin gene) and in mitochondrial DNA using a quantitative polymerase chain reaction. Treatment with 10 Gy resulted in a significant amount of DNA damage in the halo assay and reductions in the amplification of both the beta-globin gene and mitochondrial DNA. REC-1001 dose-dependently reduced the amount of damage detected in each assay, with the maximum protective effects observed at the highest REC-1001 dose evaluated (250 micro g/ml). Studies measuring the nicking of naked plasmid DNA further established the radioprotective effect of REC-1001. To elucidate possible mechanisms of action, the antioxidant properties and the free-radical scavenging activities of REC-1001 were evaluated. REC-1001 dose-dependently scavenged radiation-induced hydroxyl radicals, chemically-generated superoxide anions, stabilized DPPH radicals, and reduced Fe(3+) to Fe(2+). The results of the study indicate that the REC-1001 extract of H. rhamnoides protects mitochondrial and genomic DNA from radiation-induced damage. The polyphenols/flavonoids present in the extract might be responsible for the free radical scavenging and DNA protection afforded by REC-1001.

Topics: Animals; Biphenyl Compounds; DNA; DNA Damage; DNA, Mitochondrial; Flavonols; Free Radical Scavengers; Gamma Rays; Hippophae; Hydrazines; Hydroxyl Radical; In Vitro Techniques; Kaempferols; Male; Mice; Oxidation-Reduction; Phenols; Picrates; Plant Extracts; Quercetin; Superoxides; Thymus Gland

The present investigation was undertaken to determine the protective effects of isorhamnetin on endothelial cell line EA.hy926 injuries induced by oxidized low-density lipoprotein (ox-LDL) and to uncover some of the underlying mechanisms of these effects. Indices such as cell viability, lactate dehydrogenase (LDH), and nitric oxide (NO) release were measured to evaluate the protective effects of isorhamnetin. 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, superoxide dismutase (SOD), superoxide and reactive oxygen species (ROS) generation were also detected to evaluate the antioxidant effects of isorhamnetin. Reverse Transcription-Polymerase Chain Reaction (RT-PCR) was used to confirm the expression of endothelial nitric oxide synthase (eNOS) mRNA and lectin-like ox-LDL receptor-1 mRNA. Western blotting was used to evaluate the protein expression of this receptor and eNOS, as well as p38-mitogen-activated protein kinase (p38MAPK) phosphorylation and NF-kappaB p65 translocation. As a result, cell viability decreased significantly (P<0.01) after 24 h treatment with ox-LDL, accompanied with apparent secretion disorders such as NO reduction and LDH increase. Pretreatment with isorhamnetin resulted in remarkable increase of cell viability (P<0.05) and modulation of secretion disorders mediated by ox-LDL in a concentration-dependent manner. Besides, ox-LDL led to upregulation of lectin-like ox-LDL receptor-1, phosphorylation of p38MAPK, translocation of NF-kappaB, and downregulation of the eNOS expression in endothelial cells. Isorhamnetin pretreatment inhibited the ox-LDL-induced downregulation of eNOS, upregulation of lectin-like ox-LDL receptor-1, phosphorylation of the p38MAPK and translocation of NF-kappaB. Moreover, isorhamnetin exhibited strong antioxidant activity, which was shown by its inhibition effects on ox-LDL-induced superoxide, ROS overproduction and significant SOD reduction. The data indicated the protective effects of isorhamnetin on endothelial cell line EA.hy926 from ox-LDL-induced cell injuries. These effects were obtained via inhibition of lectin-like ox-LDL receptor-1 upregulation, interference of ox-LDL-mediated intracellular signaling pathway (p38MAPK activation, NF-kappaB nuclear translocation, eNOS expression) and the antioxidant activity of isorhamnetin.

Topics: Active Transport, Cell Nucleus; Biphenyl Compounds; Cell Line; Cell Nucleus; Cell Survival; Dose-Response Relationship, Drug; Endothelial Cells; Enzyme Activation; Flavonols; Free Radical Scavengers; Gene Expression; Humans; Hydrazines; L-Lactate Dehydrogenase; Lipoproteins, LDL; Nitric Oxide; Nitric Oxide Synthase Type III; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Picrates; Quercetin; Reactive Oxygen Species; Receptors, Oxidized LDL; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Superoxide Dismutase; Superoxides; Transcription Factor RelA

To investigate the effects of isorhamnetin 3,7-di-O-beta-D-glucopyranoside (isorhamnetin diglucoside), a major flavonoid compound of mustard leaf, on oxidative stress due to diabetes mellitus, in vivo and in vitro studies were carried out. Oral administration of isorhamnetin diglucoside (10 or 20 mg/kg of body weight/day for 10 days) to rats with streptozotocin-induced diabetes significantly reduced serum levels of glucose and 5-(hydroxymethyl)furfural (5-HMF), which is glycosylated with hemoglobin and is an indicator of oxidative stress. After intraperitoneal administration, isorhamnetin diglucoside did not show these activities. In addition, after oral administration, the thiobarbituric acid-reactive substance levels of serum, and liver and kidney mitochondria declined significantly compared with the control group in a dose-dependent manner, whereas after intraperitoneal administration these levels fell only slightly. On the basis of the oral and intraperitoneal results, it was hypothesized that isorhamnetin diglucoside was converted to its metabolite in vivo, and its conversion to its aglycone, isorhamnetin, by beta-glucosidase was confirmed; isorhamnetin acted as an antioxidant. Moreover, it was observed that isorhamnetin diglucoside had no effect on the 1,1-diphenyl-2-picrylhydrazyl radical, whereas isorhamnetin showed a potent antioxidant effect in vitro. In addition, intraperitoneal administration of isorhamnetin reduced serum glucose and 5-HMF levels. Furthermore, lipid peroxidation in blood, liver, and kidney associated with diabetes mellitus declined after the administration of isorhamnetin. These results suggest that isorhamnetin diglucoside is metabolized in vivo by intestinal bacteria to isorhamnetin and that isorhamnetin plays an important role as an antioxidant.

Topics: Animals; Antioxidants; Biphenyl Compounds; Blood Glucose; Brassica; Diabetes Mellitus, Experimental; Flavonols; Free Radical Scavengers; Furaldehyde; Glucosides; Glycated Hemoglobin; Kidney; Male; Mitochondria; Mitochondria, Liver; Picrates; Plant Leaves; Quercetin; Rats; Rats, Wistar; Thiobarbituric Acid Reactive Substances

From the leaves of Brassica juncea, an radical scavenging isorhamnetin 7-O-glucoside on peroxynitrite and 1,1-diphenyl-2-picrylhydrazyl (DPPH) was isolated and characterized based on the spectroscopic evidence. The compound showed the peroxynitrite and DPPH scavenging activities with IC50 values of 2.07 +/- 0.17 and 13.3 microM, respectively. Penicillamine and L-ascorbic acid as positive control exhibited radical scavenging activities with IC50 values of 3.17 +/- 0.39 and 12.78 microM, respectively.

Topics: Biphenyl Compounds; Flavonols; Free Radical Scavengers; Glucosides; Mustard Plant; Peroxynitrous Acid; Picrates; Plant Extracts; Plant Leaves; Quercetin