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PubMedDate not supplied

New 3-hydroxyflavanone (dihydroflavonol) phytoalexins from the papilionate legume Shuteria vestita.

Diffusates from the fungus-inoculated leaflets of Shuteria vestita have yielded four novel 3-hydroxyflavanone (dihydroflavonol) phytoalexins. From spectroscopic and chemical evidence, three of these phytoalexins have been identified as (2R,3R,2''R)--3,5,4'-trihydroxy-2'-isopropenyldihydrofurano (4'',5''; 6,7) flavanone (shuterol,1), (2R,3R)--3,5,7,4'-tetrahydroxy-6-(3,3-dimethylally) flavanone (shuterin, 2), and (2R,3R,2''R)--3,5,2',4'-tetrahydroxy-2''-isopropenyldihydrofurano (4'',5''; 6,7)flavanone (shuterone A, 3). The fourth compound (shuterone B, 4) is considered to be the 2S,3R stereoisomer of shuterone A.

Fabaceae↗

PubMed2003

Inhibition of peroxynitrite-mediated LDL oxidation by prenylated flavonoids: the alpha,beta-unsaturated keto functionality of 2'-hydroxychalcones as a novel antioxidant pharmacophore.

Prenylated 2'-hydroxychalcones and flavanones from the inflorescences of the female hop plant (Humulus lupulus) were shown to inhibit peroxynitrite-mediated oxidation of low-density lipoproteins (LDL) at low micromolar concentrations. LDL oxidation was induced by the peroxynitrite generator, 3-morpholinosydnonimine (SIN-1), and measured by the formation of conjugated dienes and thiobarbituric reactive substances. Human intake of prenylated chalcones and flavanones is mainly through beer, which contains up to 4 mg/L of these polyphenols. The two main oxidation products obtained by SIN-1 and peroxynitrite treatment of xanthohumol (XN), the principal prenylflavonoid of hops, were the aurone, auroxanthohumol (AUXN), and an endoperoxy derivative of XN, named endoperoxyxanthohumol (EPOX). In addition, the reaction produced smaller amounts of the nitro and nitroso derivatives of XN and EPOX. The formation of these nitrated products was enhanced in the presence of sodium bicarbonate (25 mM). SIN-1-induced formation of AUXN is considered to be a superoxide-mediated reaction, while the structure of EPOX points to a two electron oxidation reaction involving a Michael type addition with peroxynitrite as the nucleophile, followed by cyclization yielding a (1,2)-dioxepin-5-one ring structure. The flavanone isomer of XN, isoxanthohumol (IsoXN), unexpectedly showed a slight prooxidant effect instead of an inhibitory effect on LDL oxidation. Except for the formation of minor nitrated products, IsoXN remained largely unmodified upon treatment with SIN-1/peroxynitrite. Taken together, our results suggest that the alpha,beta-unsaturated keto functionality of chalcones is most reactive toward superoxide and peroxynitrite anions.

Antioxidants↗

PubMed2003

Relaxant effects of flavonoids in isolated guinea pig trachea and their structure-activity relationships.

The structure-activity relationships between flavonoids and their tracheal relaxant action are little known. In the present study, 26 natural and synthetic flavonoids, divided into the five classes of flavones, flavonols, flavanones, isoflavones, and chalcones, were tested, and their IC (50) values were determined. The IC (50) values of these five classes indicated that flavones were more potent than flavonols. Flavones were also more potent than flavanones suggesting that the presence of a double bond between C-2 and C-3 is important. However, flavones were similar to isoflavones in potency. Chalcones, a class with an open C-ring, appeared to be the least potent among these five classes. Introduction of a hydroxy group at position C-6 of flavones increases their relaxant activities. So does adding a hydroxy group at position C-7 of flavones. It appears that the optimal number of hydroxy groups introduced to the A-ring of flavones is one. As more hydroxy groups are introduced to positions at C-5, C-6, and/or C-7 of flavones, the IC (50) values increase. It seems that flavones or flavonols with a pyrogallol moiety either in the A- or B-ring, respectively, have no activity. It appears that flavonols with ortho-hydroxy groups in the B-ring are more potent than those with meta-hydroxy groups. The activity of 6-hydroxyflavone disappears if the C-6 hydroxy group of the A-ring is methoxylated. If the C-4' hydroxy group of the B ring is methoxylated, the relaxant effect of these flavones is also attenuated or disappears. Therefore, the hydroxy group on either the A- or B-ring of flavones and flavonols being methylated resulted in lower potency of the tracheal relaxant effects. However, when all hydroxy groups on both the A- and B-rings of flavones or flavonols are methoxylated this results in higher potency. Therefore, the influence of methoxylation in flavones may be similar to that in flavonols. However, if the C-3 hydroxy group on the C-ring of flavonols, but not flavones which lack this hydroxy group, is methoxylated, the relaxant effects may increase. Glycosylation of the hydroxy group at position C-7 of flavones or flavanones attenuates the relaxant effects.

Animals↗

PubMed1985

Naringin levels in citrus tissues : I. Comparison of different antibodies and tracers for the radioimmunossay of naringin.

The preparation of a tritiated radiotracer that was used in the radioimmunoassay of naringin (naringenin-7-O-alpha-rhamnosyl- (1-2)-beta-d-glucopyranoside) and which was synthesized by reduction of the carbonyl group of the flavanone is reported. The resulting assay has a detection limit of 0.5 picomole per 0.1 milliliter, is specific for the 7-neohesperidoside substitution on flavanones, and can measure naringin in crude extracts of plant tissues. This radioimmunoassay is compared with three other naringin immunoassays which use antibodies raised against two different haptens and different tracers labeled with (125)I or (3)H. The applicability of the methods to the quantification of naringin and other flavanone neohesperidosides in citrus tissue is discussed.

Journal Article↗

PubMed2004

Flavonoids promote cell migration in nontumorigenic colon epithelial cells differing in Apc genotype: implications of matrix metalloproteinase activity.

Colonic epithelial cell migration is required for movement up to the apex of the crypt and, hence, normal differentiated cell function. This migratory phenotype is dependent upon wild-type adenomatous polyposis coli (Apc) expression. The purpose of this study is to determine whether specific flavonoids induce cell migration in colon epithelial cells either wild type or heterozygous for Apc genotype. Nontumorigenic murine colon epithelial cell lines with distinct Apc genotypes, young adult mouse colon (YAMC; Apc+/+) cells, and Immortomouse/Min colon epithelial (IMCE; Apc(Min/+)) cells were used to assess the ability of specific flavonoids to induce cell migration relative to migration induced by hepatocyte growth factor (HGF). The citrus flavanones naringenin and hesperetin did not induce cell migration comparable with HGF in either cell type. However, the glycosylated forms of these flavanones, naringin and hesperidin, induced migration differentially in YAMC and IMCE cells. Specifically, naringin and hesperidin induced the greatest migratory response in IMCE cells at 1 microM (P < 0.01) and induced migration greater than untreated control cells (P < 0.05) but equal to HGF-treated cells. In YAMC cells, hesperidin did not induce migration except at the 100-microM concentration. Apigenin induced migration in IMCE cells at 1 (P < 0.05) and 50 microM (P < 0.01) and did not induce migration in the YAMC cells. Catechin induced migration at the highest concentration (300 microM) only in the IMCE cells, whereas epicatechin induced migration at the lowest concentration only (1 microM) in IMCE cells. Overall, the glycosylated citrus flavanones induced the greatest migratory response at the lowest concentration in IMCE cells. Co-treatment of IMCE cells with the global matrix metalloproteinase (MMP) inhibitor Ilomastat in the presence of naringin, hesperidin, or apigenin demonstrated that flavonoid-induced migration was dependent on MMP activity. Induction of the migratory phenotype by flavonoids in these models of preneoplastic epithelial cells suggests a novel mechanism for colon cancer prevention.

Animals↗

PubMedDate not supplied

Anti-inflammatory and antinociceptive activity of flavonoids isolated from Viscum album ssp. album.

Viscum album L. has been used in the indigenous systems of medicine for treatment of headache and some inflammatory diseases. In order to evaluate this information, antinociceptive and anti-inflammatory activities of the five flavonoids (5,7-dimethoxy naringenin or 4',6'-dimethoxy chalcononaringenin) derivatives, isolated from the ethyl acetate fraction of the extract from V. album ssp. album, were investigated, namely 5,7-dimethoxy-flavanone-4'-O-beta-D-glucopyranoside (1), 2'-hydroxy-4',6'-dimethoxy-chalcone-4-O-beta-D-glucopyranoside (2), 5,7-dimethoxy-flavanone-4'-O-[2"-O-(5"'-O-trans-cinnamoyl)-beta-D-apiofuranosyl]-beta-D-glucopyranoside (3), 2'-hydroxy-4',6'-dimethoxy-chalcone-4-O-[2"-O-(5"'-O-trans-cinnamoyl)-beta-Dapiofuranosyl]-beta-D-glucopyranoside (4), 5,7-dimethoxy-flavanone-4'-O-[beta-D-apiofuranosyl-(1 --> 2)]-beta-D-glucopyranoside (5). For the antinociceptive activity assessment the p-benzoquinone-induced writhing test and for the anti-inflammatory activity the carrageenan-induced hind paw edema model in mice were used. The ethyl acetate fraction in a dose of 250 mg/kg as well as compounds 2 and 5 in a 30 mg/kg dose were shown to possess remarkable antinociceptive and anti-inflammatory activities per os without inducing any apparent acute toxicity as well as gastric damage.

Abdominal Pain↗

PubMed2003

Flavonoids as inhibitors of MRP1-like efflux activity in human erythrocytes. A structure-activity relationship study.

The potency of flavonoids (isoflavones, flavones, and flavanones) to inhibit efflux of 2',7'-bis-(carboxypropyl)-5(6)-carboxyfluorescein (BCPCF) from human erythrocytes was investigated. Structure-activity relationship analysis showed that the strongest inhibitors were found among flavanones bearing a hydrophobic prenyl, geranyl, or lavandulyl group at position 8 (and hydroxyl groups at 5 and 7) in ring A. A prenyl group at position 5' or stilbene at positions 4'-5' in ring B further seemed to increase inhibitor potency. The most efficient flavanones, euchrestaflavanone A and sophoraflavanone H, were approximately 20 times more efficient than genistein, and induced 50% inhibition of BCPCF efflux (IC50) at 3 microM (60 min, 37 degrees C). This is comparable to IC50 of benzbromarone (4 microM) and lower than IC50 of indomethacin (10 microM), both known MRP1 (ABCC1) inhibitors. It is suggested that BCPCF efflux is mainly due to MRP1 activity. Our results indicate that flavonoid molecular structure provides a promising base for development of potent MRP1 inhibitors.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2004

Exploring recombinant flavonoid biosynthesis in metabolically engineered Escherichia coli.

Flavonoids are important plant-specific secondary metabolites synthesized from 4-coumaroyl coenzyme A (CoA), derived from the general phenylpropanoid pathway, and three malonyl-CoAs. The synthesis involves a plant type III polyketide synthase, chalcone synthase. We report the cloning and coexpression in Escherichia coli of phenylalanine ammonia lyase, cinnamate-4-hydroxylase, 4-coumarate:CoA ligase, and chalcone synthase from the model plant Arabidopsis thaliana. Simultaneous expression of all four genes resulted in a blockage after the first enzymatic step caused by the presence of nonfunctional cinnamate-4-hydroxylase. To overcome this problem we fed exogenous 4-coumaric acid to induced cultures. We observed high-level production of the flavanone naringenin as a result. We were also able to produce phloretin by feeding cultures with 3-(4-hydroxyphenyl)propionic acid. Feeding with ferulic or caffeic acid did not yield the corresponding flavanones. We have also cloned and partially characterized a new tyrosine ammonia lyase from Rhodobacter sphaeroides. Tyrosine ammonia lyase was substituted for phenylalanine ammonia lyase and cinnamate-4-hydroxylase in our E. coli clones and three different growth media were tested. After 48 h induction, high-level production (20.8 mg L(-1)) of naringenin in metabolically engineered E. coli was observed for the first time.

Arabidopsis↗

PubMed2005

Molecular mechanisms of the naringin low uptake by intestinal Caco-2 cells.

Naringin, the main flavanone of grapefruit, was reported to display numerous biological effects: antioxidant, hypocholesteremic, anti-atherogenic and favoring drug absorption. Naringin absorption mechanisms were studied in Caco-2 cells (TC7 clone). We investigated the possible involvement of several membrane transporters implicated in polyphenolic compounds intestinal transport (sodium-dependent glucose transporter 1, monocarboxylate transporter, multidrug-associated resistance proteins 1 and 2, and P-glycoprotein). Naringin was poorly absorbed by Caco-2 cells, according to its low value of apparent permeability coefficient (P(app) = 8.1 +/- 0.9 x 10(-8) cm/s). In the presence of verapamil, a specific inhibitor of P-glycoprotein, cellular uptake was increased by almost threefold after 5 min, and P(app) was doubled after 30 min. Our results indicated the involvement of P-glycoprotein, an ATP-driven efflux pump, capable of transporting naringin from the Caco-2 cell to the apical side. This phenomenon could explain, at least in part, the low absorption of this flavanone at the upper intestinal level.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2007

NMR assignments of unusual flavonoids from the kino of Eucalyptus citriodora.

Two unusual flavonoids, 3,5,4',5''-tetrahydroxy-7-methoxy-6-[1-(p-hydroxy-phenyl)ethyl]flavanone (1) and 3,5,7,4',5''-pentahydroxy-6-[1-(p-hydroxy-phenyl)ethyl] flavanone (2), were isolated from the kino of Eucalyptus citriodora. Structural elucidation of the new compounds were established on the basis of spectral data, particularly by the use of 1D NMR and several 2D shift-correlated NMR pulse sequences ((1)H, (1)H-COSY, HMQC, HMBC).

Carbon Isotopes↗

PubMedDate not supplied

Validated methods for the quantification of biologically active constituents of poplar-type propolis.

The validation of rapid, low-cost spectrophotometric procedures for the quantification of the three main groups of bioactive substances (flavones and flavonols, flavanones and dihydroflavonols, and total phenolics) in poplar-type propolis has been performed. A spectrophotometric assay based on the formation of an aluminium chloride complex was applied for the quantification of total flavones and flavonols using galangin as standard. Because of the high amount of flavanones and dihydroflavonols in "poplar type" propolis, the introduction of a distinct procedure for their quantification was considered of special significance and the DAB9 colorimetric method was applied for the purpose. Total phenolic content was measured by the Folin-Ciocalteu procedure using a mixture of pinocembrin and galangin as a reference. The procedures were validated using a model mixture of compounds representing the poplar-type propolis composition as found in previous studies. The accuracy (recovery) varied in the range 84-109%, and the relative standard deviation was 0.5-6.2%. The developed spectrophotometric procedures were applied to six poplar type propolis samples. The results were verified independently by a HPLC procedure. The two sets of results agreed satisfactory, as proven by Student's t-test.

Anti-Infective Agents↗

PubMed1986

[The antioxidant activity of citrus fruit peels].

The antioxidant properties of freeze-dried citrus fruit peels (orange, lemon, grapefruit) and methanolic extracts from the peel were studied. Freeze-dried orange peel showed the highest, lemon peel somewhat less and grapefruit peel the lowest but still remarkable antioxidant activity. This could be significantly improved by preparing methanolic extracts of the peels. Comparative examinations and autoxidation studies with the flavanon glycosides hesperidin and naringin as well as with their aglycones hesperetin and naringenin showed that the former are mainly responsible for the antioxidative activity of the citrus peel and extracts. In order to compare their antioxidative activity with that of the commercially available natural antioxidants alpha-tocopherol and ascorbylpalmitate, the freeze-dried citrus peels and their methanolic extracts should be used in higher concentrations, in consideration of their peculiar properties and complex natural composition. Furthermore, aspects of the correlation between antioxidant activity and molecular structure of the flavanones were discussed.

Antioxidants↗

PubMed2006

Effect of different flavonoids on collagen synthesis in human fibroblasts.

In this study, we discovered that flavonoids belonging to the subclasses: (flavanone, flavone, and flavonol) display differential effects on the synthesis of collagen in human dermal fibroblasts. At 80 microg/ml flavonoids quercetin-3,3',4', 5,7-pentahydroxyflavone, 3-methyl quercetin, and 7-hydroxyflavone significantly decreased the total protein concentration which was a direct consequence of their cytotoxic effect, while naringenin exhibited no effect on total collagen and total protein concentration. Quercetin-3,3'4',7-tetramethyl ether, 4'-hydroxyflavanone, flavanone, and fisetin significantly decreased collagen concentration while morin, rutin, and chrysin increased collagen concentration without changing the overall protein concentration. The initial screening performed in this study enables the identification of compounds that exert significant effects on fibroblast function and show potential as starting material for pharmaceutical preparations targeted against various disorders centered around disturbed collagen metabolism.

Collagen↗

PubMed2004

Colonic metabolism of dietary polyphenols: influence of structure on microbial fermentation products.

The metabolism of chlorogenic acid, naringin, and rutin, representative members of three common families of dietary polyphenols, the hydroxycinnamates, the flavanones, and the flavonols, respectively, was studied in an in vitro mixed culture model of the human colonic microflora. Time- and concentration-dependent degradation of all three compounds was observed, which was associated with the following metabolic events after cleavage of the ester or glycosidic bond: reduction of the aliphatic double bond of the resulting hydroxycinnamate caffeic acid residue; dehydroxylation and ring fission of the heterocyclic C-ring of the resulting deglycosylated flavanone, naringenin, and of the deglycosylated flavonol, quercetin (which differed depending on the substitution). The metabolic events, their sequences, and major phenolic end products, as identified by GC-MS or LC-MS/MS, were elucidated from the structural characteristics of the investigated compounds. The major phenolic end products identified were 3-(3-hydroxyphenyl)-propionic acid for chlorogenic acid, 3-(4-hydroxyphenyl)-propionic acid and 3-phenylpropionic acid for naringin, and 3-hydroxyphenylacetic acid and 3-(3-hydroxyphenyl)-propionic acid for rutin. The degree of degradation of the compounds studied was significantly influenced by the substrate concentration as well as individual variations in the composition of the fecal flora. The results support extensive metabolism of dietary polyphenols in the colon, depending on substrate concentration and residence time, with resultant formation of simple phenolics, which can be considered biomarkers of colonic metabolism if subsequently absorbed. It is also apparent that a relatively small number of phenolic degradation products are formed in the colon from the diverse group of natural polyphenols.

Chromatography, High Pressure Liquid↗

PubMed2006

Exotic flora dependence of an unusual Brazilian propolis: the pinocembrin biomarker by capillary techniques.

Significant amounts of pinocembrin (>10%), a dihydroxy-flavanone, was found in the composition of an unusual brand of a subtropical Brazilian propolis. Incidentally, this sealing material was obtained from hives surrounding a large forestry site based on a single exotic flora, namely poplar (Populus sp.). Examination of the different botanical parts of poplar revealed the buds as the main source of the flavanone. Techniques used for the establishment of the chemical correlation between the propolis brand and the poplar buds were TLC/densitometry, capillary GC-MS in the e.i. mode, and CZE with DAD monitoring. Since color enhancement after Al3+ complexation applies just for more hydroxylated flavonoids, the alternative techniques herein applied were of value for pinocembrin detection and estimation. Analytical data indicated the dominance of the main phenolic pinocembrin biomarker as well as the presence of other related flavonoids in the botanical source and in the propolis derived thereof.

Aluminum↗

PubMed2005

Antimicrobial and radical scavenging flavonoids from the stem wood of Erythrina latissima.

From the stem wood of Erythrina latissima, two isoflavones and a flavanone were isolated and characterized as 7,3'-dihydroxy-4'-methoxy-5'-(gamma,gamma-dimethylallyl)isoflavone (erylatissin A), 7,3'-dihydroxy-6'',6''-dimethyl-4'',5''-dehydropyrano [2'',3'': 4',5']isoflavone (erylatissin B), (-)-7,3'-dihydroxy-4'-methoxy-5'-(gamma,gamma-dimethylallyl)flavanone (erylatissin C), respectively, in addition to 10 known flavonoids. Structures of these compounds were determined on the basis of their spectroscopic data. These compounds showed antimicrobial activity against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Candida mycoderma. The isolated compounds also exhibited weak radical scavenging properties towards DPPH radical.

Anti-Infective Agents↗

PubMed2002

Antimicrobial constituents from the stem bark of Feronia limonia.

The stem bark of Feronia limonia (Fam. Rutaceae) yielded (-)-(2S)-5,3'-dihydroxy-4'-methoxy-6",6"-dimethylchromeno-(7,8,2",3")-flavanone along with several known compounds including an alkaloid, five coumarins, a flavanone, a lignan, three sterols and a triterpene. The structures of these compounds were determined by spectroscopic methods, mainly 1D and 2D NMR. The antimicrobial screening of compounds by a microdilution technique resulted in MICs in the range 25-100 microg/ml. Other biological activities of the known compounds are also discussed.

Alkaloids↗

PubMed2003

Flavonol synthase from Citrus unshiu is a bifunctional dioxygenase.

Flavonol synthase was classified as a 2-oxoglutarate-dependent dioxygenase converting natural (2R,3R)-dihydroflavonols, i.e. dihydrokaempferol, to the corresponding flavonols (kaempferol). Flavonol synthase from Citrus unshiu (Satsuma mandarin), expressed in Escherichia coli and purified to homogeneity, was shown to accept also (2S)-naringenin as a substrate, producing kaempferol in high yield and assigning sequential flavanone 3beta-hydroxylase and flavonol synthase activities to the enzyme. In contrast, dihydrokaempferol was identified as the predominant product from assays performed with the unnatural (2R)-naringenin as substrate. The product which was not converted any further on repeated incubations was identified by 1H NMR and CD spectroscopies as (-)-trans-dihydrokaempferol. The data demonstrate that Citrus flavonol synthase encompasses an additional non-specific activity trans-hydroxylating the flavanones (2S)-naringenin as well as the unnatural (2R)-naringenin at C-3.

Chromatography, Thin Layer↗