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At least 163 records · Page 9Linked to original sources
PubMed1988

Cloning of the two chalcone flavanone isomerase genes from Petunia hybrida: coordinate, light-regulated and differential expression of flavonoid genes.

In this paper we report the isolation of cDNA clones encoding the flavonoid-biosynthetic enzyme chalcone flavanone isomerase (CHI) from Petunia hybrida. A nearly full size cDNA clone, isolated from a corolla-specific expression library, was characterized by sequence analysis. Using this CHI cDNA and the previously cloned flavonoid-specific chalcone synthase (CHS) cDNA we show that CHI and CHS genes are coordinately and tissue-specifically expressed in a developmental and light-regulated manner. Furthermore, coordinate induction of both mRNAs is observed after continuous irradiation of Petunia plantlets with UV light, probably as part of the plants UV defence mechanism. The two CHI genes, denoted A and B, were isolated from a genomic library of the Petunia inbred line V30. Both genes are transcriptionally active: gene A is transcribed in corolla, tube and UV-irradiated plantlets (1.0 kb mRNA), whereas gene B is only transcribed in immature anthers (1.0 kb mRNA). In combination with Southern blot analysis these data implicate the presence of two distinct non-allelic CHI genes in the genome of the P. hybrida line V30. Unexpectedly, mature anthers accumulate a 0.3 kb larger CHI RNA. This RNA is transcribed from CHI gene A and has a 0.3 kb 5' extension relative to the gene A transcript found in corolla tissue. Furthermore it is neither coordinately expressed with CHS mRNA nor UV inducible. Its biological function is still obscure, since no active CHI enzyme could be demonstrated in the same tissue.

Acyltransferases↗
PubMed1995

Molecular topology and quantum chemical descriptors in the study of reversed-phase liquid chromatography. Hydrogen-bonding behavior of chalcones and flavanones.

The reversed-phase liquid chromatographic hydrophobicity parameters (log K'w and S) of several chalcones and flavanones were determined with methanol:water mobile phases of different compositions and with trace quantities of n-decylamine and 1-octanol added to the eluent to minimize the silanophilic interactions present in alkylsilane-bonded phases. It has been reported that qualitative hydrogen bonding information can be obtained from the relationship between S and log K'w determined with these chromatographic conditions. To quantitatively describe the hydrogen-bonding discrimination effects observed for the compounds under study, the parameter delta was defined as follows: delta(s-log kw) = S-log K'w. With topological and molecular orbital calculations, several molecular descriptors were computed for test compounds, and multivariate statistical techniques were used to examine the informative value of the parameter proposed. The results obtained indicate that delta(s-log Kw) encodes structural information mainly related to the molecular polarity and the ability of compounds to participate in hydrogen-bonding interactions. Similar structural information was also obtained for delta(s-log Kw) values of 31 structurally dissimilar compounds.

Aniline Compounds↗
PubMed1996

Cloning of chalcone-flavanone isomerase cDNA from Pueraria lobata and its overexpression in Escherichia coli.

Chalcone-flavanone isomerase (CHI) cDNA was isolated from Pueraria lobata by combination of cDNA library screening using Phaseolus vulgaris CHI cDNA as a probe and polymerase chain reaction techniques. Analysis of nucleotide sequence of the cloned cDNA revealed a 675-bp open reading frame encoding a 225-amino-acid polypeptide with a molecular weight of 23,803 Da. The CHI cDNA coding region was cloned into pET-3d expression vector and successfully overexpressed in Escherichia coli cells as active CHI enzyme. The recombinant CHI was then purified to apparent homogeneity by DEAE-cellulose column chromatography. Replacement of Cys-119 with Ala was carried out by site-directed mutagenesis and the result that the mutant CHI showed CHI enzyme activity confirmed that Cys-119 is not involved in the CHI catalytic active site.

Amino Acid Sequence↗
PubMed1991

Inoculation of Vicia sativa subsp. nigra roots with Rhizobium leguminosarum biovar viciae results in release of nod gene activating flavanones and chalcones.

Flavonoids released by roots of Vicia sativa subsp. nigra (V. sativa) activate nodulation genes of the homologous bacterium Rhizobium leguminosarum biovar viciae (R. l. viciae). Inoculation of V. sativa roots with infective R. l. viciae bacteria largely increases the nod gene-inducing ability of V. sativa root exudate (A.A.N. van Brussel et al., J Bact 172: 5394-5401). The present study showed that, in contrast to sterile roots and roots inoculated with R. l. viciae cured of its Sym plasmid, roots inoculated with R. l. viciae harboring its Sym plasmid released additional nod gene-inducing flavonoids. Using 1H-NMR, the structures of the major inducers released by inoculated roots, 6 flavanones and 2 chalcones, were elucidated. Roots extracts of (un)inoculated V. sativa contain 4 major non-inducing, most likely glycosylated, flavonoids. Therefore, the released flavonoids may either derive from the root flavonoids or inoculation with R. l. viciae activates de novo flavonoid biosynthesis.

Chalcone↗
PubMed1995

Molecular characterization and expression of alfalfa (Medicago sativa L.) flavanone-3-hydroxylase and dihydroflavonol-4-reductase encoding genes.

Flavonoids are plant phenolic compounds involved in leguminous plant-microbe interactions. Genes implied in the central branch (chalcone synthase (CHS), chalcone isomerase (CHI)) or in the isoflavonoid branch of the flavonoid biosynthesis pathway have been characterized in Medicago sativa. No information is available to date, however, on genes whose products are involved in the synthesis of other types of flavonoids. In this paper we present the genomic organization as well as the nucleotide sequence of one flavanone-3-hydroxylase (F3H) encoding gene of M. sativa, containing two introns and exhibiting 82-89% similarity at the amino acid level to other F3H proteins. This is the first report on the genomic organization of a f3h gene so far. We present also the sequence of a partial dihydroflavonol-4-reductase (DFR) M. sativa cDNA clone. Southern blot experiments indicated that f3h and dfr genes are each represented by a single gene within the tetraploid genome of M. sativa. By a combination of Northern blot and RT-PCR analysis, we showed that both f3h and dfr genes are expressed in flowers, nodules and roots, with a pattern distinct from chs expression. Finally, we show that dfr is expressed in M. sativa leaves whereas f3h is not. The role played by these two genes in organs other than flowers remains to be determined.

Alcohol Oxidoreductases↗
PubMed2006

Cloning and characterization of a flavanone 3-hydroxylase gene from Ginkgo biloba.

Flavanone 3-hydroxylase (F3H) activity is necessary for the biosynthesis of flavonoids, the main ingredients of Gingko biloba extract. The full-length cDNA and genomic DNA sequences of F3H gene were isolated from G. biloba for the first time. The full-length cDNA of G. biloba F3H gene (designated as GbF3H) contained a 1071 bp open reading frame (ORF) encoding a 357-amino-acid protein with a calculated molecular weight of about 40 kDa and isoelectric point (pI) of 5.57. The genomic DNA analysis showed that GbF3H gene had three exons and two introns. The deduced GbF3H protein showed high identities to other plant F3Hs. The conserved amino acids ligating ferrous iron and residues participating in 2-oxoglutarate binding (R-X-S) were found in GbF3H at the similar positions like other F3Hs. Three-dimensional structure modeling showed that GbF3H had a jerry roll in the enzyme core consisted of beta-sheet, a typical structure shared by all 2-oxoglutarate-dependent dioxygenases including F3Hs. Phylogenetic tree analysis revealed that GbF3H shared the same ancestor in evolution with other F3Hs and had a further relationship with other angiosperms species. Southern blot analysis indicated that GbF3H belonged to a multi-gene family. Transcription analysis revealed that GbF3H expressed in stem and leaf with the highest transcription level in leaf. The isolation and characterization of GbF3H gene will be helpful to further study the role of GbF3H gene in the biosynthesis of flavonoids in G. biloba.

Amino Acid Sequence↗
PubMed1987

A novel purification procedure for chalcone flavanone isomerase from Petunia hybrida and the use of its antibodies to characterize the Po mutation.

We have purified chalcone flavanone isomerase (CHI) from flowerbuds of Petunia hybrida to high purity. We made use of an affinity matrix consisting of Sepharose-bound Dextran Blue that is known to bind proteins containing the dinucleotide fold [S. T. Thompson, K. H. Cass, and E. Stellwagen (1975) Proc. Natl. Acad. Sci. USA 72, 669-672]. The final step, consisting of preparative elution from a denaturing acrylamide gel, yielded an approximately 2000-fold purified CHI protein. The enzyme is a single polypeptide with Mr = 29,000, and highly specific antiserum was raised against it. Using this antiserum it was shown that corolla and anther tissues express different forms of the enzyme as judged by pI. Furthermore, the absence of immunoreactive CHI was demonstrated in a mutant of P. hybrida (genotype popo) which accumulates 2',4,4',6'-tetrahydroxy-chalcone in anthers as a consequence of lack of enzyme activity.

Animals↗
PubMed1990

Reaction mechanism of oxidative rearrangement of flavanone in isoflavone biosynthesis.

Microsomes that were prepared from elicitor-treated Pueraria lobata cell cultures catalyzed the conversion of liquiritigenin, a flavanone, into daidzein, an isoflavone. The reaction was resolved into two steps. 2, 7, 4'-Trihydroxyisoflavonone was formed as a major product when liquiritigenin was incubated with carefully washed microsomes in the presence of NADPH. The structure of 2, 7, 4'-trihydroxyisoflavanone was confirmed by mass and 1H NMR spectroscopies. The enzyme responsible for this rearrangement reaction is a cytochrome P-450-dependent monooxygenase. Upon treatment with a soluble enzyme fraction 2, 7, 4'-trihydroxyisoflavone yielded daidzein quantitatively. The incorporation of 18O from 18O2 into the 2-hydroxy group of 2, 7, 4'-trihydroxyisoflavanone was demonstrated by the shift of molecular ion in its mass spectrum. Based on these observations a new reaction mechanism, hydroxylation associated with 1,2-migration, is proposed for the oxidative rearrangement reaction catalyzed by the cytochrome P-450 enzyme of Pueraria lobata.

Cytochrome P-450 Enzyme System↗
PubMed2006

Isolation and in vitro antibacterial activity of astilbin, the bioactive flavanone from the leaves of Harungana madagascariensis Lam. ex Poir. (Hypericaceae).

Harungana madagascariensis is well known for its topical antibacterial properties used in the elaboration of a lot of skin hygiene products. The aim of this study was, on the one hand, to evaluate the in vitro antibacterial activities of aqueous, ethanolic and ethyl acetate crude extracts of Harungana madagascariensis leaves against bacterial strains representative of skin microflora and, on the other hand, to determine the chemical structure of the active compound. Only the ethyl acetate leaf extract presented important antibacterial activity. Its fractionation was carried out by column chromatography using silica gel 60 and it yielded 11 fractions. A bioautographic method, revealed in these fractions the presence of a flavanone as the active compound astilbin or 3-O-alpha-L-rhamnoside-5,7,3',4'-tetrahydroxydihydroflavonol which was identified on the basis of its spectroscopic data. Concerning the antibacterial activity against the representative skin microflora of the armpit and feet, MIC and MBC ranged from 25 to 250 and 100 to 750 microg ml-1, respectively. The results showed that some bacteria considered to be responsible for bad odours at the armpit and feet levels, were destroyed at 200 microg ml-1 (MBC), a concentration sparing most of the useful saprophytic microflora. The minimal inhibitory quantity (MIQs) of astilbin ranged from 50 to 100 microg.

Acetates↗
PubMed1998

Identification of a cytochrome P450 cDNA encoding (2S)-flavanone 2-hydroxylase of licorice (Glycyrrhiza echinata L.; Fabaceae) which represents licodione synthase and flavone synthase II.

The microsome of insect cells expressing CYP Ge-5 (CYP93B1), a cytochrome P450 cDNA of licorice (Glycyrrhiza echinata L.), catalyzed the formation of [14C]licodione and [14C]2-hydroxynaringenin from (2S)-[14C]liquiritigenin and (2S)-[14C]naringenin, respectively. On acid treatment, the products were converted to 14C-labeled 7,4'-dihydroxyflavone and apigenin. Eriodictyol was also converted to luteolin by the reaction with the microsome of yeast expressing CYP93B1 and subsequent acid treatment. CYP93B1 was thus shown to encode (2S)-flavanone 2-hydroxylase, which has previously been designated to licodione synthase and flavone synthase II depending on the substrates employed.

Animals↗
PubMed2000

Flavanone 8-dimethylallyltransferase in Sophora flavescens cell suspension cultures.

Dimethylallyl diphosphate: naringenin 8-dimethylallyltransferase (EC 2.5.1) was characterized. The enzyme was enantiospecific for (-)-(2S)-naringenin and utilized 3,3-dimethylallyl diphosphate as sole prenyl donor. It required Mg2+ (optimum concentration, 10 mM), and has an optimum pH of 9-10. The apparent Km values for 3,3-dimethylallyl diphosphate and naringenin were 120 and 36 microM, respectively. The microsomal fraction prenylated several other flavanones at the C-8 position less effectively as compared with naringenin. Interestingly, when 2'-hydroxynaringenin was used as a prenyl acceptor, the 8-lavandulyl (sophoraflavanone G) and the 6-dimethylallyl derivatives were formed, together with the 8-dimethylallyl derivative, leachianone G. These results suggest that the 2'-hydroxy group of naringenin plays an important role for the formation of a lavandulyl group.

Alkyl and Aryl Transferases↗
PubMed2000

Flavanones and 3-hydroxyflavanones from Lonchocarpus oaxacensis.

The roots of the tropical tree Lonchocarpus oaxacensis afforded the 3-hydroxyflavanones jayacanol and mundulinol, as well as two flavanones, mundulin and minimiflorin. Flavonoids bearing 6,7-(dimethylpyran) and 8-(gammagamma-dimethyl allyl) substituents are characteristic for species grouped in the Minimiflori subsection. Therefore this subsection seems to be chemically and morphologically homogeneous. The antifungal activity of the four isolated compounds was tested against the wood rotting fungus Postia placenta, but only jayacanol was active.

Antifungal Agents↗
PubMed2002

Coumaronochromones and flavanones from Euchresta formosana roots.

Four coumaronochromones, formosanatins A-D (-4), and a flavanone, euchrenone a(16), along with four known compounds, euchretins E and G, euchrestaflavanone A, and daidzein, were isolated from the roots of Euchresta formosana. The structures of - were established by spectroscopic analyses.

Chromones↗
PubMed2001

Determination of flavone, flavonol, and flavanone aglycones by negative ion liquid chromatography electrospray ion trap mass spectrometry.

Eleven naturally occurring flavonoid aglycones, belonging to the representative flavone, flavonol, and flavanone types were separated by high performance liquid chromatography and analyzed on-line with negative ion electrospray ionization tandem mass spectrometry (ESI-MS/MS). In order to resolve the MS/MS spectra obtained, each compound was reinvestigated by direct loop injections using an ion trap mass spectrometer. The MSn spectra obtained allowed us to propose plausible schemes for their fragmentation supported by the analysis of five complementary synthetic flavonoid aglycones. The negative ion ESI-MS/MS behavior of the different aglycones investigated in this study revealed interesting differences when compared with the previously described patterns obtained using various ionization techniques in positive ion. Thus, concerning the retro Diels-Alder (RDA) fragmentation pathways, several structurally informative anions appeared highly specific of the negative ion mode. In addition, a new lactone-type structure, instead of a ketene, was proposed for a classic RDA diagnostic ion. We also observed unusual CO, CO2, and C3O2 losses which appear to be characteristic of the negative ion mode. All these results and these unusual neutral losses show that the negative ion mode was a powerful complementary tool of the positive ion mode for the structural characterization of flavonoid aglycones by ESI-MS/MS.

Flavonoids↗
PubMed2003

Flavanone glycosides from Miconia trailii.

Assay-guided fractionation of the ethanol extract of the twigs and leaves of Miconia trailii yielded two new flavanone glycosides, matteucinol 7-O-alpha-l-arabinopyranosyl(1-->6)-beta-d-glucopyranoside (miconioside A, 1) and farrerol 7-O-beta-d-apiofuranosyl(1-->6)-beta-d-glucopyranoside (miconioside B, 2), along with the known compounds matteucinol 7-O-beta-d-apiofuranosyl(1-->6)-beta-d-glucopyranoside (3), matteucinol (4), 2alpha,3beta,19alpha-trihydroxyolean-12-ene-24,28-dioic acid (bartogenic acid, 5), 2alpha,3beta,23-trihydroxyolean-12-ene-28-oic acid (arjunolic acid, 6), 2alpha,3alpha,19alpha, 23-tetrahydroxyurs-12-ene-28-oic acid (myrianthic acid, 7), and stigmast-4-ene-3,6-dione (8). The structures of 1-8 were elucidated by spectroscopic methods, including 2D NMR.

Cholestenones↗
PubMed2004

Estrogenic and anticarcinogenic properties of kurarinone, a lavandulyl flavanone from the roots of Sophora flavescens.

Kurarinone, a lavandulyl flavanone, was isolated from a polyphenolic extract of the roots of Sophora flavescens using fractionation guided by estrogenic activity, which was determined by recombinant yeast and Ishikawa Var-I bioassays. Kurarinone showed weak estrogenic activity both in the yeast screen and in the Ishikawa Var-I assay with EC(50) values of 4.6 and 1.66 microM, respectively. Furthermore, kurarinone was found to have potent cytotoxic activity (IC(50) value = 22.2 microM) against human MCF-7/6 breast cancer cells in the sulforhodamine-B assay.

Antineoplastic Agents, Phytogenic↗
PubMed1995

Flavanone 3-hydroxylase transcripts and flavonol accumulation are temporally coordinate in maize anthers.

Flavanone 3-hydroxylase (F3H) activity is necessary for the production of both flavonols and anthocyanins. Flavonols are required for functional pollen in maize whereas anthocyanins are non-essential pigments. A cDNA for F3H was isolated from Zea mays using a heterologous sequence from Antirrhinum majus. Comparison of the deduced amino acid sequence of maize F3H with other F3H sequences confirmed that the protein is highly conserved among widely divergent plant species. The F3H gene is present in a single copy located at the tip of chromosome 2S. High levels of F3H gene expression were detected in pigmented husk and 26-day postpollination kernels; lower levels in 18-day postpollination kernels and in coleoptiles of germinating seedlings. Slot blot analysis showed that F3H transcript levels in young seedlings are increased by high fluence-rate white light treatment in the presence of the anthocyanin regulatory gene -r. HPLC analysis of extracts from developmentally staged anthers showed that flavonol accumulation begins at the uninucleate microspore stage, continues until maturity, and is not controlled by -r. When the expression pattern of several flavonoid biosynthetic genes was analyzed during microsporogenesis, only F3H transcript accumulation was coordinate with the appearance of flavonols in anthers.

Amino Acid Sequence↗