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PubMed1988

Selectivity of neutrophil 5-lipoxygenase and cyclo-oxygenase inhibition by an anti-inflammatory flavonoid glycoside and related aglycone flavonoids.

A newly described plant-derived flavonoid, hypolaetin-8-glucoside, which has anti-inflammatory and gastroprotective actions in-vivo, and its corresponding aglycone, hypolaetin, have been compared with 14 other flavonoids for inhibition of eicosanoid generation via the 5-lipoxygenase and cyclo-oxygenase pathways in elicited rat peritoneal leukocytes stimulated with calcium ionophore. Comparable results for the inhibitory profiles of the compounds were obtained using either radioimmunoassay of released eicosanoids or radio-TLC of metabolites formed from labelled arachidonate, but there were differences in absolute potency of the inhibitors. Hypolaetin-8-glucoside was a weak but selective inhibitor of 5-lipoxygenase (IC50 56 microM vs 5-lipoxygenase; greater than 1000 microM vs cyclo-oxygenase), whereas the aglycone hypolaetin was a more potent and selective 5-lipoxygenase inhibitor (IC50 4.5 microM vs 70 microM). Results with three other glycoside/aglycone pairs confirmed that addition of sugar residues greatly reduces inhibitory potency whilst retaining selectivity against 5-lipoxygenase. Analysis of 12 aglycone flavonoids showed that inhibitory potency and selectivity against 5-lipoxygenase is conferred by the presence of 3'4'-vicinal diol (catechol) in ring B as part of a 3,4-dihydroxycinnamoyl structure as proposed by others and by incorporation of additional hydroxyl substituents. In contrast, "cross-over" of inhibitory selectivity is observed in compounds containing few hydroxyl substituents (with none in ring B) which are selective against cyclo-oxygenase. These results are discussed in relation to possible mechanisms of hypolaetin-8-glucoside's protective actions and the concept that these inhibitory effects of flavonoids cannot be ascribed to a unitary free radical scavenging action.

Animals↗
PubMed2006

Colour variation in red grapevines (Vitis vinifera L.): genomic organisation, expression of flavonoid 3'-hydroxylase, flavonoid 3',5'-hydroxylase genes and related metabolite profiling of red cyanidin-/blue delphinidin-based anthocyanins in berry skin.

BACKGROUND: Structural genes of the phenyl-propanoid pathway which encode flavonoid 3'- and 3',5'-hydroxylases (F3'H and F3'5'H) have long been invoked to explain the biosynthesis of cyanidin- and delphinidin-based anthocyanin pigments in the so-called red cultivars of grapevine. The relative proportion of the two types of anthocyanins is largely under genetic control and determines the colour variation among red/purple/blue berry grape varieties and their corresponding wines. RESULTS: Gene fragments of VvF3'H and VvF3'5'H, that were isolated from Vitis vinifera 'Cabernet Sauvignon' using degenerate primers designed on plant homologous genes, translated into 313 and 239 amino acid protein fragments, respectively, with up to 76% and 82% identity to plant CYP75 cytochrome P450 monooxygenases. Putative function was assigned on the basis of sequence homology, expression profiling and its correlation with metabolite accumulation at ten different ripening stages. At the onset of colour transition, transcriptional induction of VvF3'H and VvF3'5'H was temporally coordinated with the beginning of anthocyanin biosynthesis, the expression being 2-fold and 50-fold higher, respectively, in red berries versus green berries. The peak of VvF3'5'H expression was observed two weeks later concomitantly with the increase of the ratio of delphinidin-/cyanidin-derivatives. The analysis of structural genomics revealed that two copies of VvF3'H are physically linked on linkage group no. 17 and several copies of VvF3'5'H are tightly clustered and embedded into a segmental duplication on linkage group no. 6, unveiling a high complexity when compared to other plant flavonoid hydroxylase genes known so far, mostly in ornamentals. CONCLUSION: We have shown that genes encoding flavonoid 3'- and 3',5'-hydroxylases are expressed in any tissues of the grape plant that accumulate flavonoids and, particularly, in skin of ripening red berries that synthesise mostly anthocyanins. The correlation between transcript profiles and the kinetics of accumulation of red/cyanidin- and blue/delphinidin-based anthocyanins indicated that VvF3'H and VvF3'5'H expression is consistent with the chromatic evolution of ripening bunches. Local physical maps constructed around the VvF3'H and VvF3'5'H loci should help facilitate the identification of the regulatory elements of each isoform and the future manipulation of grapevine and wine colour through agronomical, environmental and biotechnological tools.

Anthocyanins↗
PubMed1993

Borate complexation of flavonoid-O-glycosides in capillary electrophoresis. II. Separation of flavonoid-3-O-glycosides differing in their sugar moiety.

Capillary electrophoresis was found to give significantly higher efficiency, selectivity and speed than high-performance liquid chromatography for the separation of a mixture of flavonoid-3-O-glycosides differing in their sugar moiety. Boric acid running buffer (0.2 M, pH 10.5) was used for this electrophoretic separation. The migration order in free solution capillary electrophoresis (CE) and the selectivity of these flavonoid-3-O-glycosides can be mainly explained by in situ borate complexation of both the sugar moiety and the cis-1,2-hydroxyl groups on the flavonoid skeleton and, to a lesser extent, by the ionization of hydroxyl groups on the flavonoid skeleton due to alkaline pH conditions. The correlation of the electrophoretic mobilities with the configuration and conformation of the compounds is discussed.

Anions↗
PubMed2006

Interaction of antioxidant flavonoids with tRNA: intercalation or external binding and comparison with flavonoid-DNA adducts.

Antioxidants are essential to good health. Flavonoids are powerful antioxidants, and prevent DNA damage. The antioxidative protections are related to their binding modes to a DNA duplex and complexation with free radicals in vivo. Recently we reported the interaction of flavonoids with DNA in vitro (Kanakis et al., J. Biomol. Struct. Dyn. 22, 719-724, 2005), where polyphenol different binding modes were discussed. The aim of this study was to examine the interaction of transfer RNA with quercetin (que), kaempferol (kae), and delphinidin (del) in aqueous solution at physiological conditions and to make a comparison with the corresponding pigment-DNA adducts. Constant tRNA concentration (6.25 mM) and various drug/RNA(phosphate) molar ratios of 1/48 to 1/8 were used. FTIR and UV-visible difference spectroscopic methods have been applied to determine the drug binding mode, the binding constants, and the effects of drug complexation on the stability and conformation of tRNA duplex. Both intercalative and external binding modes were observed. Structural analysis showed que, kae, and a del intercalate tRNA duplex with minor external binding to the major or minor groove and the backbone phosphate group with overall binding constants K (que) = 4.80 x 10(4) M(1), K (kae) = 4.65 x 10(4) M(1), and K (del) = 9.47 x 10(4) M(1). The stability of adduct formation is in the order of del > que > kae. A comparison with flavonoids-DNA adducts showed both intercalation and external bindings with the stability order K (que) = 7.25 x 10(4) M(1), K (kae) = 3.60 x 10(4) M(1), and K (del) = 1.66 x 10(4) M(1). Low flavonoid concentration induces helical stabilization, whereas high pigment content causes helix opening. A partial Bto A-DNA transition occurs at high drug concentration, while tRNA remains in the A-family structure.

Anthocyanins↗
PubMedDate not supplied

The effects of natural flavonoids on lipoxygenase-mediated oxidation of compounds with a benzene ring structure--a new possible mechanism of flavonoid anti-chemical carcinogenesis and other toxicities.

Numerous studies have strongly suggested that flavonoids exhibit antimutagenic, anticarcinogenic, antiallergic, and anti-inflammatory properties, but the mechanism is still far from clear. In this study, the effect of natural flavonoid compounds, such as green tea polyphenol, epigallocatechin gallate, quercetin, and rutin on lipoxygenase-mediated co-oxidation of guaiacol, benzidine, paraphenylenediamine, and dimethoxybenzidine was investigated. Green tea polyphenol, epigallocatechin gallate, quercetin, and rutin can reduce the co-oxidation reaction speed of tested compounds mediated by soybean lipoxygenase and the production of oxidative products and free radical intermediates. Their median inhibition concentrations on guaiacol oxidation mediated by soybean lipoxygenase were 8.22 mg.L-1, 17.8 micromol.L-1, 41.5 micromol.L-1, and 46.3 micromol.L-1, respectively. These were all significantly lower than glutathione, dithiothreitol, butylated hydroxyanisole and gossypol. The data collected in this study suggest that flavonoids may have an anticarcinogenicity and antitoxicity effect through inhibition of oxidative activation.

Anticarcinogenic Agents↗
PubMed2003

Effects of several polyhydroxylated flavonoids on the growth of B16F10 melanoma and Melan-a melanocyte cell lines: influence of the sequential oxidation state of the flavonoid skeleton.

The response of B16F10 melanoma and Melan-a melanocyte cell lines to treatment with five polyhydroxylated flavonoids and gallic acid, after 24 and 72 h of exposure, was determined, and the relationship between any antiproliferative effects observed and the chemical structure is discussed. After 24 h, none of the studied compounds showed significant cytotoxic activity in the B16F10 cell line, whereas compounds with an adjacent trihydroxylated substitution pattern did affect the viability of the Melan-a cell line. After 72 h of exposure, myricetin, baicalein and gallic acid significantly inhibited both B16F10 and Melan-a cell cultures, whereas luteolin and quercetin had only a moderate effect. Eriodictyol only had an effect on Melan-a cell viability, which was reduced slightly. These results suggest that the presence of a C2-C3 double bond and three adjacent hydroxyl groups in the flavonoid A- or B-rings confers greater antiproliferative activity to the flavonoid.

Animals↗
PubMed2001

Flavonoid content assay: influence of the reagent concentration and reaction time on the spectrophotometric behavior of the aluminium chloride--flavonoid complex.

The spectrophotometric assay based on aluminum chloride complex formation is one of the most commonly analytical procedures applied to flavonoid content determination. However, only a few optimization studies on the reaction conditions were done so far. The present work aims to the investigation of aluminum chloride concentration and reaction time effects on the spectrophotometric behavior of different flavonoids. The effects of both variation factors were studied by Central Composite Design and Response Surface Analysis methodology. The absorption data analysis showed that the effects of reaction time and reagent concentration on the absorption maximum are intricate and specific. A clear relationship between spectrophotometric behavior and flavonoid type or particular structure patterns could not be established.

Aluminum Chloride↗
PubMed2001

Impact of certain flavonoids on lipid profiles--potential action of Garcinia cambogia flavonoids.

Flavonoids from Cocos nucifera, Myristica fragrance, Saraka asoka and Garcinia cambogia exerted hypolipidaemic activity in rats. Lipid lowering activity was maximum in rats administered flavonoids (10 mg/kg BW/day) from Garcinia cambogia. A dose response study revealed biphasic activity. Higher doses were less effective in reducing lipid levels in serum and tissues, although devoid of toxic effects.

Animals↗
PubMed2005

Liquid chromatography-diode array detection-electrospray ionisation mass spectrometry/nuclear magnetic resonance analyses of the anti-hyperglycemic flavonoid extract of Genista tenera. Structure elucidation of a flavonoid-C-glycoside.

The anti-hyperglycemic flavonoid extract obtained from Genista tenera was first studied by liquid chromatography (LC)-diode array detection (DAD) which showed the presence of two major compounds. One of them was identified as genistein-7-O-glucoside. Luteolin-7-O-glucoside was detected as a minor constituent, while luteolin-7,3'-di-O-glucoside and rutin were found in trace amounts. LC-DAD-ESI-MS and NMR were used to confirm the structure of these compounds and allowed the elucidation of the structure of the unknown major compound, which is the flavonoid 5,7,4'-trihydroxyisoflavone-8-C-glucoside.

Carbohydrate Conformation↗
PubMed2003

Structure-dependent phytotoxicity of catechins and other flavonoids: flavonoid conversions by cell-free protein extracts of Centaurea maculosa (spotted knapweed) roots.

Invasive plants are believed to succeed in part by secretion of allelochemicals, thus displacing competing plant species. Centaurea maculosa (spotted knapweed) provides a classic example of this process. We have previously reported that spotted knapweed roots secrete (+/-)-catechin and that (-)-catechin, but not (+)-catechin, is phytotoxic and hence may be a major contributor to C. maculosa's invasive behavior in the rhizosphere. In this communication, we explore both structure/activity relationships for flavonoid phytotoxicity and possible biosynthetic pathways for root production of (+/-)-catechin. Kaempferol and dihydroquercetin were shown to be phytotoxic, while quercetin was not. Kaempferol was converted to dihydroquercetin and (+/-)-catechin when treated with total root protein extracts from C. maculosa, but quercetin was not. This finding suggests an alteration in the standard flavonoid biosynthetic pathway in C. maculosa roots, whereby kaempferol is not a dead-end product but serves as a precursor to dihydroquercetin, which in turn leads to (+/-)-catechin production.

Catechin↗
PubMed2003

A cluster of genes encodes the two types of chalcone isomerase involved in the biosynthesis of general flavonoids and legume-specific 5-deoxy(iso)flavonoids in Lotus japonicus.

Leguminous plants produce 5-deoxyflavonoids and 5-deoxyisoflavonoids that play essential roles in legume-microbe interactions. Together with chalcone polyketide reductase and cytochrome P450 2-hydroxyisoflavanone synthase, the chalcone isomerase (CHI) of leguminous plants is fundamental in the construction of these ecophysiologically active flavonoids. Although CHIs of nonleguminous plants isomerize only 6'-hydroxychalcone to 5-hydroxyflavanone (CHIs with this function are referred to as type I), leguminous CHIs convert both 6'-deoxychalcone and 6'-hydroxychalcone to 5-deoxyflavanone and 5-hydroxyflavanone, respectively (referred to as type II). In this study, we isolated multiple CHI cDNAs (cCHI1-cCHI3) from a model legume, Lotus japonicus. In contrast to previous observations, the amino acid sequence of CHI2 was highly homologous to nonleguminous CHIs, whereas CHI1 and CHI3 were the conventional leguminous type. Furthermore, genome sequence analysis revealed that four CHI genes (CHI1-3 and a putative gene, CHI4) form a tandem cluster within 15 kb. Biochemical analysis with recombinant CHIs expressed in Escherichia coli confirmed that CHI1 and CHI3 are type II CHIs and that CHI2 is a type I CHI. The occurrence of both types of CHIs is probably common in leguminous plants, and it was suggested that type II CHIs evolved from an ancestral CHI by gene duplication and began to produce 5-deoxy(iso)flavonoids along with the establishment of the Fabaceae.

Amino Acid Sequence↗
PubMed1991

Induction of sister-chromatid exchanges (SCE), polyploidy, and micronuclei by plant flavonoids in human lymphocyte cultures. A comparative study of 19 flavonoids.

Nineteen naturally occurring flavonoids were studied with regard to their SCE-inducing potency and their capability of inducing polyploidy and micronuclei in human lymphocyte cultures. The cells were treated for a period of 48 h. The flavone C-glycosides, vitexin and orientin, exhibited a moderate SCE-inducing activity, whereas the other compounds displayed only weak effects or were inactive. Polyploidy was induced by procyanidins consisting of 3 or 4 flavanol units and to a lesser extent by flavone, flavonol, and anthocyanidin aglycones. The aglycones as well as the C-glycosides and the O-glycosides, spiraeoside and luteolin-7-glucoside, were more or less active in inducing micronuclei in the lymphocytes. The flavonol O-glycosides, rutin and hyperoside, and the monomeric and dimeric flavanols failed to produce any genotoxic effects. The results are discussed with respect to a possible structure-activity relationship.

Flavonoids↗
PubMed2005

Trifluoromethylation of flavonoids and anti-tumor activity of the trifluoromethylated flavonoid derivatives.

3-Trifluoromethylflavonoid derivatives were prepared for the first time by trifluoromethylation of 3-iodoflavonoid derivatives. Other C ring and B ring trifluoromethylated flavonoid derivatives were also prepared. All the compounds were tested for their effect on the U2OS cell cycle in vitro. Bistrifluoromethylated apigenin derivative 13 showed the strongest activity against the cell growth.

Antineoplastic Agents↗
PubMed2005

Flavonoids, including an unusual flavonoid-Mg2+ salt, from roots of Cudrania cochinchinensis.

Four flavonoids with 2',4'-di-oxygenated B-rings, cochinchinol A (1), cochinchinol B (2), (2R,3R)-4',7-dihydroxy-2',5-dimethoxydihydroflavonol (3), 4',7-dihydroxy-2',5-dimethoxyflavonol (4), along with 11 known compounds, were isolated from an ethanolic extract of the roots of Cudrania cochinchinensis. Their structures were elucidated by chemical and spectroscopic methods. Cochinchinol A (1) and cochinchinol B (2) have two hitherto unprecedented flavonol salt structures in natural product chemistry. Cytotoxic activities were evaluated against several different cell lines.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Flavonoids as cycline-dependent kinase inhibitors: inhibition of cdc 25 phosphatase activity by flavonoids belonging to the quercetin and kaempferol series.

In an effort to detect potential inhibitors of cdc25 phosphatase, nineteen flavonoids belonging to the quercetin and kaempferol series have been evaluated, using a colorimetric assay of recombinant human cdc25A tyrosine phosphatase as a cell cycle-specific target. Compounds bearing two benzyl or methyl groups in positions 7 and 4' and acetyl on the hydroxy groups of the sugar moiety showed the maximal activity.

Biological Assay↗
PubMed2004

The interaction of flavonoids with membranes: potential determinant of flavonoid antioxidant effects.

Twenty six phenolic substances including representatives of the families, flavanones, flavanols and procyanidins, flavonols, isoflavones, phenolic acids and phenylpropanones were investigated for their effects on lipid oxidation, membrane fluidity and membrane integrity. The incubation of synthetic phosphatidylcholine (PC) liposomes in the presence of these phenolics caused the following effects: (a) flavanols, their related procyanidins and flavonols were the most active preventing 2,2'-azo-bis (2,4-dimethylvaleronitrile) (AMVN)-induced 2-thiobarituric acid-reactive substances (TBARS) formation, inducing lipid ordering at the water-lipid interface, and preventing Triton X-100-induced membrane disruption; (b) all the studied compounds inhibited lipid oxidation induced by the water-soluble oxidant 2,2'-azo-bis (2-amidinopropane) (AAPH), and no family-related effects were observed. The protective effects of the studied phenolics on membranes were mainly associated to the hydrophilicity of the compounds, the degree of flavanol oligomerization, and the number of hydroxyl groups in the molecule. The present results support the hypothesis that the chemical structure of phenolics conditions their interactions with membranes. The interactions of flavonoids with the polar head groups of phospholipids, at the lipid-water interface of membranes, should be considered among the factors that contribute to their antioxidant effects.

Amidines↗