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PubMed1994

The structure-activity relationships of flavonoids as inhibitors of cytochrome P-450 enzymes in rat liver microsomes and the mutagenicity of 2-amino-3-methyl-imidazo[4,5-f]quinoline.

The antimutagenicity of 19 naturally occurring flavonoids and their derivatives including flavones, flavonols, flavanones, isoflavones and flavanols were determined using Salmonella typhimurium TA98 against 2-amino-3-methylimidazo[4,5-f] quinoline (IQ) in the presence of Aroclor 1254-induced rat hepatic S9. In general, a relationship between the chemical structure of flavonoids and their antimutagenicity was found for compounds containing one or more of the following features: (i) C4 keto group, (ii) aglycone, (iii) double bond at positions C2 and C3, (iv) phenyl group at position C2, and (v) three hydroxy substituents at positions C4', C5 and C7. The inhibitory effects of flavonoids on activities of 7-ethoxycoumarin deethylase (ECD) and 7-ethoxyresorufin deethylase (ESD) of Aroclor 1254-induced hepatic microsomes were also examined. In addition, we studied the effects of flavonoids on the metabolism of IQ by Aroclor 1254-induced microsomes using high-performance liquid chromatography. The antimutagenicity correlated with the inhibition of cytochrome P-450IA1-linked ESD and P-450IA2-linked ECD activity in hepatic microsomes, and with an inhibition of N-hydroxy-IQ formation from IQ metabolism by hepatic microsomes. These results indicated that flavones or flavonols that contain C5, C7 and C4' hydroxyl groups are potent inhibitors of P-450 enzyme activities induced by Aroclor 1254 (P-450IA1 and P-450IA2), and may potentially be useful as chemopreventive agents against heterocyclic amine-induced mutagenesis or carcinogenesis.

7-Alkoxycoumarin O-Dealkylase↗
PubMed2006

Chinese herbal ingredients are effective immune stimulators for chickens infected with the Newcastle disease virus.

This study was conducted to determine the efficacy of 4 Chinese herbal ingredients (CHI) as immune stimulators for an active vaccine in chickens using both in vitro and in vivo assays. The CHI used were Astragalus polysaccharide (APS), Isatis root polysaccharide (IRPS), Propolis polysaccharide, and Epimedium flavone at various concentrations. Two hundred 14-d-old male White Roman chickens were randomly divided into 10 groups. Chickens in groups 1 to 9 were inoculated with the New-castle disease virus (NDV) strain IV vaccine by intranasal and intraocular administration. Chickens in groups 1 to 8 were also administered subcutaneously on the dorsal region of the neck with 0.5 mL of the corresponding CHI at 2 doses: 29 and 58 mg/kg of BW for APS and IRPS and 7.25 and 14.5 mg/kg of BW for the others, once daily for 3 successive days. In group 9 (CHI-free control) and group 10 (both vaccine- and CHI-free control), chickens were injected with 0.5 mL of physiological saline. New-castle disease virus-specific serum hemagglutination inhibition antibody (Ab) production in immunized chickens was quantified using established methods. The results indicate that a majority of the CHI used at appropriate concentrations were effective in enhancing in vitro proliferation of chick embryo fibroblasts in response to the NDV infection. In vivo administration of CHI to vaccinated chickens (7.25 to 58 mg/kg of BW, depending on type) increased serum anti-NDV hemagglutination inhibition Ab titer concentrations, compared with the administration the NDV alone. For all CHI, a beneficial effect on the Ab production was observed on d 21 after the initiation of the vaccination. On the basis of the in vivo doses used, Propolis polysaccharide and Epimedium flavone were more potent than APS and IRPS in promoting the humoral immune response in the young birds (P < 0.05). Collectively, these findings suggest that appropriate doses of CHI can be used as novel, effective immune stimulators for chickens.

Animals↗
PubMedDate not supplied

Evaluation of acidic heteropolysaccharide structures in Rhizobium leguminosarum biovars altered in nodulation genes and host range.

1H-NMR spectroscopy showed that the extracellular heterpolysaccharides (EPS) from derivatives of Rhizobium leguminosarum bv. trifolii ANU843 altered in pSym nod composition or function (transposon insertions, deletion of pSym, induction by flavone, and introduction of cloned pSym nod regions from ANU843 and R. l. bv. viciae 248 on recombinant plasmids into the pSym-cured background of ANU843) differed only in 3-hydroxybutyrate stoichiometry per octaglycosyl unit. This change in EPS was likely to be an indirect effect of altered growth during expression of pSym nod genes in the presence of the flavone. No modifications were found in EPS made by R. l. bv. phaseoli 8002 when its resident pSym was deleted or replaced with pSym from R. l. bv. viciae 248, or with a derivative of this pSym lacking the host-specific nodulation genes nodFELMNTO. Thus, although certain O-acyl noncarbohydrate substitutions in EPS are affected by pSym nod genes (including the ones that determine host range) in certain backgrounds of R. leguminosarum, this change does not occur universally among all strains of R. leguminosarum. We conclude that the structure of the acidic EPS does not control host-specific nodulation of white clover, hairy vetch, and beans for the strains of R. leguminosarum tested here.

Gene Expression↗
PubMed1993

Ascorbic acid-enhanced antiproliferative effect of flavonoids on squamous cell carcinoma in vitro.

We examined the effects of flavone and two polyhydroxylated plant flavonoids (quercetin and fisetin), either singly or in combination with ascorbic acid, on the growth of a human squamous cell carcinoma cell line (HTB 43) in vitro. Fisetin and quercetin significantly impaired cell growth in the presence of ascorbic acid. Exposure of cells to ascorbic acid (2 micrograms/ml) and 2 micrograms/ml of either fisetin or quercetin resulted in 61 and 45% inhibition of cell growth, respectively, in 72 h, while treatment with ascorbic acid alone had no effect on cellular proliferation. Flavone and ascorbic acid, either as single agents or in combination, exhibited no significant inhibition at any of the concentrations tested. The enhancement of the antiproliferative effect of the above flavonoids by ascorbic acid may be due to its ability to protect these compounds against oxidative degradation.

Adjuvants, Pharmaceutic↗
PubMed1992

Cytokine induction and therapeutic synergy with interleukin-2 against murine renal and colon cancers by xanthenone-4-acetic acid derivatives.

Derivatives of xanthenone-4-acetic acid (XAA) have been found to have similar activity to flavone-8-acetic acid against transplantable solid tumors. Some of these compounds were compared to flavone acetic acid (FAA) in their ability to induce cytokines as well as to mediate antitumor effects against murine renal cancer (Renca) and a mouse colon cancer (MCA-38). 5-Methyl-XAA and 5-chloro-XAA proved to be more potent than FAA on a mg/kg basis for induction of the genes for IFN alpha, IFN gamma, and TNF alpha, and for IFN and TNF activities in the sera of treated mice. These effects were sharply dose dependent. On the other hand, 7-methyl-XAA, which has no antitumor activity, did not induce these genes. In addition, 5-methyl-XAA and 5-chloro-XAA but not 7-methyl-XAA synergized with recombinant human interleukin-2 (rhIL-2) for the treatment of Renca and MCA-38. Doses of the active derivatives that failed to induce cytokines also exhibited no therapeutic synergy with rhIL-2. These results suggest that at least some of the antitumor effects of these XAA derivatives are related to their ability to induce cytokines.

Animals↗
PubMed1994

Biochemical Plant Responses to Ozone (IV. Cross-Induction of Defensive Pathways in Parsley (Petroselinum crispum L.) Plants).

Parsley (Petroselinum crispum L.) is known to respond to ultraviolet irradiation by the synthesis of flavone glycosides, whereas fungal or elicitor stress leads to the synthesis of furanocoumarin phytoalexins. We tested how these defensive pathways are affected by a single ozone treatment (200 nL L-1; 10 h). Assays were performed at the levels of transcripts, for enzyme activities, and for secondary products. The most rapid transcript accumulation was maximal at 3 h, whereas flavone glycosides and furanocoumarins were maximally induced at 12 and 24 h, respectively, after the start of ozone treatment. Ozone acted as a cross-inducer because the two distinct pathways were simultaneously induced. These results are consistent with the previously observed ozone induction of fungal and viral defense reactions in tobacco, spruce, and pine.

Journal Article↗
PubMed2005

Antibacterial 4-amino-N-(5-methylisoxazol-3-yl)-N-[(4-oxo-2-phenyl-4H-1-benzopyran-6-yl)methyl]benzenesulfonamide.

In the molecule of the title compound, C26H21N3O5S, a new type of sulfonamide derivative with potential antibacterial activity, the flavone moiety is almost planar. The isoxazole and aminophenyl rings are also planar and make dihedral angles of 77.0 (2) and 81.4 (1) degrees , respectively, with the best plane of the flavone ring system. The crystal structure is stabilized by intra- and intermolecular hydrogen bonds.

Anti-Bacterial Agents↗
PubMed1991

Structure of 8-(2,6-dideoxy-beta-ribo-hexopyranosyl)-5-hydroxy-2-(4- hydroxyphenyl)-7-methoxy-4H-1-benzopyran-4-one sesquihydrate, aciculatin.

C22H22O8.1.5H2O, Mr = 441.4, monoclinic, I2, a = 21.037 (7), b = 7.371 (2), c = 27.512 (4) A, beta = 100.34 (2) degrees, V = 4196.8 (8) A3, Z = 8, Dx = 1.397 g cm-3, lambda (Mo K alpha) = 0.71073 A, mu = 1.029 cm-1, F(000) = 1864, T = 295 K, final R (on F) = 0.058 for 2113 observed reflections with I greater than or equal to 2 sigma (I). Aciculatin crystallizes as a sesquihydrate with two independent molecules per asymmetric unit. The 2,6-dideoxy-beta-ribo-hexopyranosyl ring is linked to C8 of the flavone through a beta-C-glycosidic bond. Intramolecular hydrogen bonding occurs between the hydroxyl and ketonic O atoms of the flavone ring system.

Flavonoids↗
PubMed1990

Role of the nodD and syrM genes in the activation of the regulatory gene nodD3, and of the common and host-specific nod genes of Rhizobium meliloti.

To analyse the regulation of the nodulation (nod) genes of Rhizobium meliloti RCR2011 we have isolated lacZ gene fusions to a number of common, host-range and regulatory nod genes, using the mini-Mu-lac bacteriophage transposon MudII1734. Common (nodA, nodC, nod region IIa) and host-range (nodE, nodG, nodH) genes were found to be regulated similarly. They were activated (i) by the regulatory nodD1 gene in the presence of flavones such as chrysoeriol, luteolin and 7,3',4'-trihydroxyflavone, (ii) by nodD2 in the presence of alfalfa root exudate but not with the NodD1-activating flavones, and (iii) by the regulatory genes syrM-nodD3 even in the absence of plant inducers. Thus common and host-range nod genes belong to the same regulon. In contrast to the nodD1 gene, the regulatory nodD3 gene was not expressed constitutively and exhibited a complex regulation. It required syrM for expression, was activated by nodD1 in the presence of luteolin and was positively autoregulated.

DNA, Bacterial↗
PubMed1993

Biochemical studies of a new class of alcohol dehydrogenase inhibitors from Radix puerariae.

Two potent, reversible inhibitors of human alcohol dehydrogenase (ADH) isozymes were isolated from Radix puerariae (RP, commonly known as kudzu root) and identified as the isoflavones diadzein and genistein. The 4'-methoxy derivatives of daidzein (trivial name, formononetin) and genistein (biochanin A), minor constituents of RP, were also shown to be ADH inhibitors. All of these isoflavones inhibit the human gamma 2 gamma 2-ADH isozyme competitively with respect to ethanol and uncompetitively with respect to NAD+. A survey of more than 40 structurally related compounds revealed one more isoflavone (prunetin) and four flavones (7-hydroxyflavone, apigenin, galangin, and kaempferol) that inhibit ADH. The isoflavone inhibitors, however, are far more potent than the flavone inhibitors. Among the isoflavones studied, genistein is the most potent with Ki = 0.1 microM toward gamma 2 gamma 2-ADH. Human ADH isozymes differ in their sensitivity to these inhibitors in the order gamma 2 gamma 2-, gamma 1 gamma 1- > alpha alpha-, pi pi- > chi chi-ADH. These inhibitors do not affect the beta 1 beta 1- and beta 2 beta 2-ADH isozymes at concentrations as high as 20 microM. Rat and rabbit class I ADHs are also inhibited by these isoflavone inhibitors. The 7-O-glucosyl derivatives of daidzein, genistein, formononetin, and biochanin A do not inhibit ADH, but are potent aldehyde dehydrogenase inhibitors.

Alcohol Dehydrogenase↗
PubMed1998

Flavonoids reduce morphine withdrawal in-vitro.

The effects of quercetin, flavone, catechin and chrysin on the naloxone-precipitated withdrawal contracture of the acute morphine-dependent guinea-pig ileum have been investigated in-vitro. After 4 min in-vitro exposure to morphine a strong contracture of guinea-pig isolated ileum was observed after the addition of naloxone. All the flavonoids, injected 10 min before morphine at concentrations between 10(-7) and 10(-5) M, were capable of blocking naloxone-induced contracture after exposure to morphine in a concentration-dependent fashion. IC50 values calculated for quercetin, flavone, catechin and chrysin were 2.7 x 10(-6), 7.3 x 10(-7), 8.5 x 10(-7) and 5.3 x 10(-6) M, respectively. These results suggest that flavonoids might play an important role in the control of morphine withdrawal.

Acetylcholine↗
PubMed1999

Molecular characterization of binding of substrates and inhibitors to DT-diaphorase: combined approach involving site-directed mutagenesis, inhibitor-binding analysis, and computer modeling.

The molecular basis of the interaction of DT-diaphorase with a cytotoxic nitrobenzamide CB1954 [5-(aziridin-1-yl)-2, 4-dinitrobenzamide] and five inhibitors was investigated with wild-type DT-diaphorase (human and rat) and five mutants [three rat mutants (rY128D, rG150V, rH194D) and two human mutants (hY155F, hH161Q)]. hY155F and hH161Q were generated to evaluate a hypothesis that Tyr155 and His161 participate in the obligatory two-electron transfer reaction of the enzyme. The catalytic properties of hY155F and hH161Q were compared with a naturally occurring mutant, hP187S. Pro187 to Ser mutation disturbs the structure of the central parallel beta-sheet, resulting in a reduction of the binding affinity of the flavin-adenine dinucleotide prosthetic group. With NADH as the electron donor and menadione as the electron acceptor, the k(cat) values for the wild-type human DT-diaphorase, hY155F, hH161Q, and hP187S were measured as 66 +/- 1, 23 +/- 0, 5 +/- 0 and 8 +/- 2 x 10(3) min(-1), respectively. Because hY155F still has significant catalytic activity, the hydroxyl group on Tyr155 may not be as important as proposed. Interestingly, hY155F was found to be 3. 3 times more active than the human wild-type DT-diaphorase in the reduction of CB1954. Computer modeling based on our results suggests that CB1954 is situated in the active site, with the aziridinyl group pointing toward Tyr155 and the amide group placed near a hydrophobic pocket next to Tyr128. Dicoumarol, Cibacron blue, chrysin, 7,8-dihydroxyflavone, and phenindone are competitive inhibitors of the enzyme with respect to nicotinamide coenzymes. The binding orientations of dicoumarol, flavones, and phenindone in the active site of DT-diaphorase were predicted by results from our inhibitor-binding studies and computer modeling based on published X-ray structures. Our studies generated results that explain why dicoumarol is a potent inhibitor and binds differently from flavones and phenindone in the active site of DT-diaphorase.

Antineoplastic Agents↗
PubMed2004

Agonist-induced internalization of leukotriene B(4) receptor 1 requires G-protein-coupled receptor kinase 2 but not arrestins.

The leukotriene B(4) (LTB(4)) receptor (BLT1) becomes desensitized upon repeated agonist stimulation. Little is known, however, about BLT1 internalization, which follows desensitization in most G-protein-coupled receptors (GPCR). In the current study, transiently expressed BLT1 readily internalized, after LTB(4) stimulation, in RBL-2H3 cells that express high levels of endogenous GPCR kinase 2 (GRK2) but did not in COS-7 or human embryonic kidney (HEK) 293 cells, which do not overexpress GRK. The internalization of BLT1 could be blocked in RBL-2H3 cells by coexpressing dominant-negative (DN) GRK2 K220R and could be promoted in HEK293 cells by coexpressing wild-type (WT) GRK2. Coexpression of WT or DN nonvisual arrestins had no effect on BLT1 internalization. Moreover, upon stimulation with LTB(4), BLT1 did not induce arrestin-green fluorescence protein redistribution in either cell type, even in the presence of overexpressed GRK2. Coimmunoprecipitation experiments confirmed that BLT1 could associate with GRK2 but not with arrestins. A C-tail-truncated mutant of BLT1 lost the capacity to internalize and associate with GRK2 upon exposure to LTB(4), suggesting that the C-tail was required for receptor internalization and association with GRK2. Taken together, our results indicate that the C terminus of BLT1 plays a pivotal role in receptor internalization and GRK2 association. Moreover, ligand-induced BLT1 internalization is dependent on GRK2 but independent of arrestins. This may allow differential, cell-type-specific signaling in response to LTB(4), depending on GRK expression levels.

Animals↗
PubMed1992

Chemotaxis of Rhizobium meliloti towards Nodulation Gene-Inducing Compounds from Alfalfa Roots.

Luteolin, a flavone present in seed exudates of alfalfa, induces nodulation genes (nod) in Rhizobium meliloti and also serves as a biochemically specific chemoattractant for the bacterium. The present work shows that R. meliloti RCR2011 is capable of very similar chemotactic responses towards 4',7-dihydroxyflavone, 4',7-Dihydroxyflavanone, and 4,4'-dihydroxy-2-methoxychalcone, the three principal nod gene inducers secreted by alfalfa roots. Chemotactic responses to the root-secreted nod inducers in capillary assays were usually two- to four-fold above background and, for the flavone and flavonone, occurred at concentrations lower than those required for half-maximal induction of the nodABC genes. Complementation experiments indicated that the lack of chemotactic responsiveness to luteolin seen in nodD1 and nodA mutants of R. meliloti was not due to mutations in the nod genes, as previously thought. Thus, while nod gene induction and flavonoid chemotaxis have the same biochemical specificity, these two functions appear to have independent receptors or transduction pathways. The wild-type strain was found to suffer selective, spontaneous loss of chemotaxis towards flavonoids during laboratory subculture.

Journal Article↗
PubMed1996

Chemotactic Preferences and Strain Variation in the Response of Phytophthora sojae Zoospores to Host Isoflavones.

The zoospores of Phytophthora sojae are chemotactically attracted to the isoflavones genistein and daidzein that are released by soybean roots. In this study we have examined the response of P. sojae zoospores to a wide range of compounds having some structural similarity to genistein and daidzein, including isoflavones, flavones, chalcones, stilbenes, benzoins, benzoates, benzophenones, acetophenones, and coumarins. Of 59 compounds examined, 43 elicited some response. A comparison of the chemotactic responses elicited by the various compounds revealed a primary role for the phenolic 4(prm1)- and 7-hydroxyl groups on the isoflavone structure. A few compounds acted as repellents, notably methylated flavones with a hydrophobic B ring. The chemotactic response to many of the analogs was markedly different among different strains of P. sojae.

Journal Article↗
PubMed2005

Epoxide formation on the aromatic B ring of flavanone by biphenyl dioxygenase of Pseudomonas pseudoalcaligenes KF707.

Prokaryotic dioxygenase is known to catalyze aromatic compounds into their corresponding cis-dihydrodiols without the formation of an epoxide intermediate. Biphenyl dioxygenase from Pseudomonas pseudoalcaligenes KF707 showed novel monooxygenase activity by converting 2(R)- and 2(S)-flavanone to their corresponding epoxides (2-(7-oxabicyclo[4.1.0]hepta-2,4-dien-2-yl)-2, 3-dihydro-4H-chromen-4-one), whereby the epoxide bond was formed between C2' and C3' on the B ring of the flavanone. The enzyme also converted 6-hydroxyflavanone and 7-hydroxyflavanone, which do not contain a hydroxyl group on the B-ring, to their corresponding epoxides. In a previous report (S.-Y. Kim, J. Jung, Y. Lim, J.-H. Ahn, S.-I. Kim, and H.-G. Hur, Antonie Leeuwenhoek 84:261-268, 2003), however, we found that the same enzyme showed dioxygenase activity toward flavone, resulting in the production of flavone cis-2',3'-dihydrodiol. Extensive structural identification of the metabolites of flavanone by using high-pressure liquid chromatography, liquid chromatography/mass spectrometry, and nuclear magnetic resonance confirmed the presence of an epoxide functional group on the metabolites. Epoxide formation as the initial activation step of aromatic compounds by oxygenases has been reported to occur only by eukaryotic monooxygenases. To the best of our knowledge, biphenyl dioxygenase from P. pseudoalcaligenes KF707 is the first prokaryotic enzyme detected that can produce an epoxide derivative on the aromatic ring structure of flavanone.

Bacterial Proteins↗
PubMed2003

CFTR activation in human bronchial epithelial cells by novel benzoflavone and benzimidazolone compounds.

Activators of the CFTR Cl- channel may be useful for therapy of cystic fibrosis. Short-circuit current (Isc) measurements were done on human bronchial epithelial cells to characterize the best flavone and benzimidazolone CFTR activators identified by lead-based combinatorial synthesis and high-throughput screening. The 7,8-benzoflavone UCcf-029 was a potent activator of Cl- transport, with activating potency (<1 microM) being much better than other flavones, such as apigenin. The benzimidazolone UCcf-853 gave similar Isc but with lower potency (5-20 microM). In combination, the effect induced by maximal UCcf-029 and UCcf-029, UCcf-853, and apigenin increased strongly with increasing basal CFTR activity: for example, Kd for activation by UCcf-029 decreased from >5 to <0.4 microM with increasing basal Isc from approximately 4 microA/cm2 to approximately 12 microA/cm2. This dependence was confirmed in permeabilized Fischer rat thyroid cells stably expressing CFTR. Our results demonstrate efficacy of novel CFTR activators in bronchial epithelia and provide evidence that activating potency depends on basal CFTR activity.

Amiloride↗
PubMed2007

Flavonoids and the risk of renal cell carcinoma.

Intake of flavonoids has been inversely related to the risk of various common neoplasms, but limited data exist on renal cell carcinoma (RCC). We used data from a case-control study conducted between 1994 and 2002 in four Italian areas to study the relation between major flavonoid classes and RCC. The study included 767 cases with incident, histologically confirmed RCC and 1,534 hospital controls admitted for acute, nonneoplastic conditions and matched with cases by study center, sex, and quinquennia of age. We applied published data on food and beverage content of six major classes of flavonoids to dietary information collected through a validated food frequency questionnaire. After adjustment for major recognized confounding factors and total energy intake, the odds ratios for subjects in the highest versus the lowest quintile of intake were 0.80 [95% confidence interval (95% CI), 0.58-1.11] for total flavonoids, 0.76 (95% CI, 0.56-1.03) for isoflavones, 0.94 (95% CI, 0.60-1.47) for anthocyanidins, 0.77 (95% CI, 0.56-1.06) for flavan-3-ols, 0.90 (95% CI, 0.67-1.21) for flavanones, 0.68 (95% CI, 0.50-0.93) for flavones, and 0.69 (95% CI, 0.50-0.95) for flavonols. Allowance for vegetable and fruit consumption only partly explained these inverse relations. Thus, flavonoids, and particularly flavones and flavonols, may account, at least in part, for the favorable role of plant foods on RCC.

Adult↗