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At least 145 records · Page 8Linked to original sources
PubMed2003

A maize QTL for silk maysin levels contains duplicated Myb-homologous genes which jointly regulate flavone biosynthesis.

The maize p1 locus coincides with a major QTL (quantitative trait locus) determining levels of maysin, a C-glycosyl flavone that deters feeding by corn ear-worm. The p1 gene is tightly linked with a second gene, p2, and both genes encode similar Myb-domain proteins. We show here that maize cell cultures transformed with either the p1 or p2 genes expressed under a constitutive promoter accumulate transcripts for flavonoid biosynthetic genes, and synthesize phenylpropanoids and C-glycosyl flavones related to maysin. Additionally, maize plants that are deleted for the p1 gene have reduced maysin levels and moderate silk-browning reaction, whereas plants with a deletion of both p1 and p2 have non-detectable silk maysin and non-browning silks. We conclude that both p1 and p2 induce maysin biosynthesis in silk, although the two genes differ in their expression and pigmentation effects in other tissues. These results show that a QTL for flavone biosynthesis actually comprises two tightly linked genes with related functions.

Flavones↗
PubMed1990

Microbiological transformation of flavone and isoflavone.

1. Flavone and isoflavone were subjected to microbial transformation studies. Screening with 80 fungal species showed that flavone was transformed by a large number of microorganisms and in higher yields than isoflavone. 2. Large-scale fermentations of flavone followed by isolation and characterization of metabolites using spectroscopic analysis showed the formation of 4'-hydroxyflavone, 3',4'-dihydroxyflavone and two cleavage products identified as o-hydroxyphenyl-hydroxymethyl ketone and 1-(o-hydroxyphenyl)-1,2-ethanediol. However, fermentation of isoflavone gave only 4'-hydroxyisoflavone and 3',4'-dihydroxyisoflavone.

Biotransformation↗
PubMed1999

Effect of flavone in a canine model of myocardial stunning.

Putative cardioprotective action of flavone (10, 20 and 30 mg/kg) was investigated in a canine model of regional ischemia (20 min) followed by 60 min of reperfusion. In animals pretreated with vehicle, myocardial stunning was evidenced by significant changes in hemodynamic parameters (depressed mean arterial pressure, LV peak (+) dP/dt, LV peak (-) dP/dt and elevated LV end-diastolic pressure) and biochemical parameters (decreased myocardial ATP and rise in plasma malondialdehyde or MDA; a marker of free radical-induced injury). A reduction in plasma MDA was noted with 20 and 30 mg/kg flavone, although attenuation of myocardial dysfunction was evident with all the three doses. The results suggest that besides a significant dose-dependent antioxidant effect, flavone may also have some cardioprotective actions per se, which needs to be further investigated.

Adenosine Triphosphate↗
PubMed2001

Modulation by insulin rather than blood glucose of the pain threshold in acute physiological and flavone induced antinociception in mice.

The present study investigated the cause effect relationship between glycemic and algesic states. The hypo- and hyperglycemic conditions were induced physiologically through exercise (3 min swim at room temperature 28 degrees - 30 degrees C) and external dextrose (2 g/kg, ip) administration respectively in mice. Besides, flavone (50 mg/kg, sc) a known antinociceptive drug was chosen to study such a cause effect relationship. The anti-nociception was assessed by acetic acid assay, blood glucose measured using glucometer (Ames) and serum insulin by radioimmunoassay. The findings revealed that irrespective of the glycemic state whether hypo-, hyper, or euglycemic induced by swim stress, dextrose or flavone per se respectively, significant antinociceptive response was recorded. Pretreatment with flavone (50 mg/kg, sc) always exhibited a tendency to reverse the hyperglycemia, if any, but enhanced the antinociceptive response either after swim stress or after dextrose. These data support the contention that changes in the glycemic state in acute condition is not responsible for antinociceptive response and thereby suggesting dissociation between these two parameters. Extended studies estimating serum insulin level after the above mentioned maneuvers showed a significant rise whenever antinociceptive response was recorded irrespective of the glycemic state. It is suggested that serum insulin level, a hormonal parameter rather than the blood glucose level, which is a metabolic parameter, appears more reliable. It appears that the changes in serum insulin level produced by various treatments may have a relationship with the antinociceptive response. However, this study has the limitation that the results can apply only for acute conditions and extrapolation to clinical conditions is debatable.

Acetic Acid↗
PubMed2003

Flavone and isoflavone phytoestrogens are agonists of estrogen-related receptors.

While estrogen-related receptors (ERRalpha, ERRbeta, and ERRgamma) share a high amino acid sequence homology with estrogen receptors (ERs), estrogens are not ligands of ERRs. Structure-function studies from this and other laboratories have revealed that ERRs have small ligand-binding pockets and have provided evidence to show that these receptors can activate gene transcription in a constitutive manner. To address the question as to whether there is any agonist for ERRs, our laboratory recently performed virtual ligand screening on ERRalpha that predicted flavone and isoflavone phytoestrogens to be ligands of this receptor. Our mammalian cell transfection and mammalian two-hybrid experiments revealed that three isoflavones (genistein, daidzein, and biochanin A) and one flavone (6,3',4'-trihydroxyflavone) behaved as agonists of ERRs. These phytoestrogens induced the activity of ERRalpha at concentrations that are comparable to those for the activation of ERalpha and ERbeta. In this study, we also used the results of ERRalpha ligand-binding site mutant, F232A, to verify our ERRalpha hypothetical computer model. Our recent ERR research has determined for the first time that flavone and isoflavone phytoestrogens are agonists of ERRs. In addition, our studies have demonstrated that an approach that combines structure-based virtual screening and receptor functional assays can identify novel ligands of orphan nuclear receptors.

Binding, Competitive↗
PubMed2005

[Quick optimization of high performance liquid chromatographic conditions for separation of flavones of Astragalus].

An analytical method for flavones of Astragalus has been developed and a process of high performance liquid chromatographic (HPLC) condition optimization has been elaborated. The LC retention parameters of 34 components were obtained quickly by using three linear gradient elutions. Overlapping separation range map (OSRM), which is related to the separation quality and the analysis time, was utilized to search the optimised stepwise gradient method for HPLC analysis of flavones of Astragalus. Finally, the optimised stepwise gradient elution conditions were set up with the help of this map. Under the optimised conditions, the sample of flavones of Astragalus was well separated in reasonable time. The method is more convenient than that using a series of isocratic elutions.

Astragalus Plant↗
PubMed2006

[Study of microwave-assisted extraction on total flavones content in Hibiscus manihot L. flower].

OBJECTIVE: To study the extraction process of the total flavones content in Hibiscus manihot L. flower. METHODS: it was investigated that effect of ethanol concentration, extracting time, power of microwave oven and Solid/Liquid ratio (g/mL) on total flavones content using the orthogonal design. RESULTS: The optimum microwave-assisted extraction conditions included: ethanol concentration of 70%, extraction time of 30s, the power of microwave oven of 360w, solid/liquid ratio of 1 : 50 (g/ml) and granularity < or = 80 pore. CONCLUSION: There are broad possibilities for the extraction of the total flavones content from Hibiscus manihot L flower using Microwave-assisted technigue.

Drugs, Chinese Herbal↗
PubMed2006

[Two new flavones from Fordia cauliflora of Yunnan].

AIM: To study the chemical constituents of the stem of Fordia cauliflora of Yunnan province. METHODS: The constituents were separated and purified by repeated silica column chromatography. The structures were elucidated by physical-chemical properties and spectroscopic data. RESULTS: Six compounds were isolated from the ethanol extract of the stem of Fordia cauliflora. They were identified as: 6-hydroxy-3-methoxy-6",6"-dimethylchromeno-(2", 3" : 7, 8)-flavone (1), 3-methoxy-6-(3-methyl-but-2-enyloxy)-6", 6"-dimethylchromeno-( 2", 3" : 7, 8)-flavone (2), 3, 6-dimethoxy-6", 6"-dimethylchromeno-( 2", 3" : 7, 8)-flavone (3), 7-hydroxy-4'-methoxyisoflavone (4), 7, 4'-dihydroxyisoflavone (5) and karanjin (6). CONCLUSION: Compounds 1 and 2 are new compounds. Compounds 3 -5 were isolated from the plant for the first time.

Fabaceae↗
PubMedDate not supplied

Identification of lipophilic flavones and flavonols by comparative HPLC, TLC and UV spectral analysis.

The identification of lipophilic flavones and flavonols using a combination of high performance liquid chromatography, thin layer chromatography and UV spectral analysis is discussed. Data are provided for the flavones, apigenin, luteolin and tricetin and twelve of their methyl ethers, 8-hydroxyluteolin, 6-hydroxyluteolin and scutellarein and fourteen of their methyl ethers, and some 6,8-dihydroxyapigenin and 6,8-dihydroxyluteolin derivatives. Data for some forty two flavonols with extra 6- and/or 8-hydroxylation, mostly 6-hydroxykaempferol and quercetagetin derivatives, are also presented. The remaining compounds analysed include fourteen 5-deoxyflavones, four 5-methoxyflavones and five 5-deoxyflavonols plus further 5-hydroxylated flavones and flavonols without B-ring oxidation or with 2'-, 5'- or 6'-hydroxylation.

Chromatography, High Pressure Liquid↗
PubMed2003

Fungicidal potential of methoxylated flavones from citrus for in vitro control of Colletotrichum gloeosporioides, causal agent of anthracnose disease in tropical fruits.

Four polymethoxylated flavones (3,5,6,7,3',4'-hexamethoxyflavone, 3,5,6,7,8,3',4'-heptamethoxyflavone, 5,6,7,8,4'-pentamethoxyflavone and 5,6,7,8,3',4'-hexamethoxyflavone) were isolated and characterized from cold-pressed orange oil. Their antifungal activities were evaluated against Colletotrichum gloeosporioides (Penz) Penz & Sacc, a major plant pathogen of fruits that causes significant damage to crops in tropical, sub-tropical and temperate regions. Methoxylated flavones were effective in inhibiting mycelial growth of the fungus. As flavone concentration increased, mycelial growth decreased. 5,6,7,8,3',4'-Hexamethoxyflavone completely inhibited the growth of Cgloeosporioides at a concentration of 100 microg ml(-1).

Citrus↗
PubMed1981

Studies on the mechanism of stimulation of microsomal H2O2 formation and benzo(a)pyrene hydroxylation by substrates and flavone.

The addition of activators like flavone and hexobarbital to hepatic microsomes markedly stimulates H2O2 formation. The similar increase observed with flavone of microsomal hydroxylation of benzo(a)pyrene and its inhibition by catalase and methanol suggests but does not prove a necessary interaction of microsomal H2O2 production with benzo(a)pyrene hydroxylation. Hexobarbital and flavone-stimulated H2O2 formation is optimal at a stoichiometric relationship of these activators and NADPH. This implies either their direct participation as electron donors or their indirect involvement in electron transport by facilitation of stoichiometric substrate cytochrome P-450/NADPH flavoprotein interactions. Steady state kinetics data are consistent with a scheme in which the formation in microsomes of a complex of 1 mole of NADPH with NADPH-cytochrome P-450 reductase and 1 mole hexobarbital with cytochrome P-450 regulates H2O2 formation.

Animals↗
PubMed1992

Flavones are inhibitors of HIV-1 proteinase.

Substituted gamma-chromones were found to weakly inhibit HIV-1 proteinase, an important enzyme in the replication and processing of the AIDS virus. Chromones bearing hydroxyl substituents and a phenolic group at the 2-position (flavones) were the most active compounds and structure-activity relationships for a limited series of flavone inhibitors are presented. Dixon plots are reported and a possible mechanism for flavone-induced inhibition is proposed. The results are also compared with those for some structurally related non-peptidic inhibitors of HIV-1 proteinase. Since some flavonoid compounds have already been shown to have antiviral activity against AIDS, the present observations of anti-HIV-1 proteinase activity may be particularly significant.

Chromones↗
PubMed1992

Organotin-flavone complexes: a new class of fluorescent probes for F1F0ATPase.

Fluorescent 5-coordinate organotin-flavone complexes of 3-hydroxy-flavone (Hof) and 3,5,7,2',4',-pentahydroxyflavone (morin) are good inhibitors of mitochondrial F1F0ATPase but do not inhibit F1-ATPase and they have been examined as possible fluorescent probes of F1F0ATPase. R2SnX (morin) complexes exhibit low fluorescence enhancement on binding to mitochondrial membranes with no displacement by equimolar tributyltin. In contrast R2SnX (of) complexes exhibit high fluorescence enhancement whose extent is variable and is displacable by equimolar tributyltin. Fluorescence enhancement by R2SnX (of) complexes correlates with the ATPase I50 values. Dialkyltin-3-hydroxy flavone, R2SnX(of), complexes act as a new class of fluorescent probes which titrate the F0 segment of F1F0ATPase.

Animals↗
PubMed1990

Analgesic activity of certain flavone derivatives: a structure-activity study.

Flavone and 10 hydroxy and glucoside flavone derivatives were synthesised. They were tested for their analgesic effect in mice employing acetic acid-induced writhing and tail immersion methods. Subcutaneously all the tested compounds exhibited significant analgesic activity with varying potencies in both assay models. The activity of flavone and its 5-; 7-; 2'-; 5,7- and 7,8-hydroxy derivatives apparently involves an opiate-like mechanism, since their activity was reversed by naloxone pretreatment. It is suggested that flavonoid substances may utilise more than one mechanism in eliciting analgesia.

Analgesics↗
PubMed1988

Stability of flavone-8-acetic acid (LM975) in aqueous solutions by high-performance liquid chromatography.

A high-performance liquid chromatographic method has been developed to investigate the stability of solutions of flavone-8-acetic acid (LM975) during preparation and storage. LM975 (20 microg ml(-1) in PBS) was found to be completely stable for 10 days at 80 degrees C as long as light was rigorously excluded. The drug showed no significant adsorption to containers of different materials or to two filtration units tested. Drug degradation did occur however, on exposure to light. In normal laboratory light the t(0.95) (5% degraded) was 30.3 min, in intense natural light (laboratory window sill) the t(0.95) was 3.3 min and in intense artificial light (100 W bulb at 10 cm) the t(0.95) was 13.8 min. NMR and mass spectral analysis of the isolated degradation product implied the formation of the decarboxylated product, 8-methyl flavone. It is suggested that care be taken to exclude light during the preparation, storage and infusion of solutions of flavone-8-acetic acid.

Journal Article↗
PubMed2004

Effects of ethanol extract of propolis (EEP) and its flavones on inducible gene expression in J774A.1 macrophages.

Propolis, a bee-hive product, has been used in folk medicine for centuries, and recently in modern medicine as an anti-inflammatory and immunomodulatory agent. These activities would be mainly due to phenolic compounds such as flavonoids, especially flavone derivatives. The present study examined the effect of ethanol extract of propolis (EEP) and selected flavone derivatives (chrysin, galangin, kaempferol and quercetin) on interleukin-1beta (IL-1beta) and inducible nitric oxide synthase (iNOS) gene expression in lipopolysaccharide (LPS)-induced J774A.1 macrophages. Treatment of cells with EEP significantly suppressed both IL-1beta mRNA (P<0.02) and iNOS mRNA (P<0.001) expression. The concentrations of cytokine in cell culture supernatants and cell lysates and nitric oxide (NO) generation were reduced in a dose-dependent manner. The tested phenolic compounds significantly decreased the IL-1beta mRNA level and IL-1beta protein concentration (P<0.05) (excluding galangin), iNOS mRNA level and NO production (P<0.001). The most potent inhibitor of the IL-1beta synthesis and NO generation was chrysin. These results indicate that EEP exerts its inhibitory effect on the IL-1beta and iNOS gene expression in J774A.1 macrophages at the transcriptional level. Tested flavone derivatives contribute to the anti-inflammatory activity of propolis.

Animals↗
PubMed2004

Flavones and polyphenols inhibit the NO pathway during apoptosis of leukemia B-cells.

We recently reported that resveratrol, a grape-derived polyphenol, in vitro induces the apoptosis of leukemic B-cells and simultaneously inhibits the production of endogenous nitric oxide (NO) through inducible NO synthase (iNOS) down-regulation. The same results were observed in the present study with not only acetate derivatives of polyphenols, particularly the pentaacetate of -viniferin (resveratrol dimer), but also with a synthetic flavone (a diaminomethoxyflavone) in both leukemia B-cell lines and B-cell chronic lymphocytic leukemia (B-CLL) patients' cells. Moreover, flavopiridol, another flavone already known for its pro-apoptotic properties in B-CLL cells, was also found to down-regulate both iNOS expression and NO production. Thus, inhibition of the NO pathway during apoptosis of leukemia B-cells appears a common mechanism for several compounds belonging to two distinct families of phytoalexins, the flavones and grape-derived polyphenols.

Annexin A5↗
PubMed2000

Isolation and characterization of methoxylated flavones in the flowers of Primula veris by liquid chromatography and mass spectrometry.

Characterization of six flavones, which were named substances G1, G2, G3, G4, G5 and G6 according to their R(F) values in normal-phase thin-layer chromatography, is reported. The pure flavones were purified after maceration with methanol by normal-phase solid-phase extraction, normal-phase medium-pressure liquid chromatography, normal-phase preparative thin-layer chromatography and preparative reversed-phase high-performance liquid chromatography (RP-HPLC). The collected fractions of several isolation steps were analyzed by normal-phase (NP) and RP-HPLC. Detection and identification of the substances G was accomplished by UV detection at 213-216 nm, diode array UV detection, or fluorescence detection (lambda(ex)=330 nm; lambda(cm)=440 nm). The molecular mass, the elementary composition, and the structure of the six components was determined by electron-impact high-resolution mass spectrometry (EI-HRMS). Substance G4 was identified as 3',4',5'-trimethoxyflavone. The substances G1-G6 were shown to be mono-, di- tri- and pentamethoxyflavones. HPLC-electrospray ionization tandem mass spectrometry (ESI-MS-MS) of the flavones was carried out employing a 150x2 mm I.D. column packed with a 3 microm/100 A octadecylsilica stationary phase and a mobile phase comprising 1.0% acetic acid in water-acetonitrile (50:50). Comparative RP-HPLC-ESI-MS of the raw methanol extract and the isolated substances G1-G6 proved that the isolated compounds were pure and were not artifacts. Finally, RP-HPLC-ESI-MS-MS was used to identify substances G1-G6 in phytopharmaceutical drugs.

Chromatography, High Pressure Liquid↗