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PubMed2000

New antimicrobial flavanones from Physena madagascariensis.

Two new flavanones (1 and 2) with antibacterial activity were isolated from the methanolic extract of the dried leaves of Physena madagascariensis using activity against Staphylococcus aureus to guide the isolation. A third flavonoid, a flavanone dimer linked by a methylene group (3) was also isolated and proved to be inactive. The structures of 1 and 2 were established primarily from NMR studies, while that of 3 required more extensive mass spectrometric analysis. All three flavanones had lavandulyl units in the limonene form. Flavanones 1 and 2 were active against several bacteria at concentrations as low as 4 microM.

Anti-Bacterial Agents↗

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↗

PubMed2004

Synthesis of deuterium-labeled flavanones.

Deuterium incorporation at the C-3 position of flavanones was achieved by treatment of flavanones and 2'-hydroxychalcones with D3PO4 and AcOD. We propose that the deuteration reaction mechanism for 2'-hydroxychalcones substrates is as follows. In the first step, 2'-hydroxychalcones cyclize to the corresponding flavanones by an intramolecular Michael-type reaction. Then deuteriums are incorporated into the flavanones via enolization.

Chalcone↗

PubMed1987

Effect of flavanone on mixed-function oxidase and conjugation reactions in rats.

Flavanone administered to female Fischer 344 rats (1.00 mmol/kg per day for seven days) did not induce ethylmorphine demethylation, aniline hydroxylation, hexobarbital oxidation or aldrin epoxidation. Flavanone at 0.05 mmol/kg per day for seven days increased glutathione-S-transferase activity with 1,2-dichloro-4-nitrobenzene and 1,2-epoxy-3-(p-nitrophenoxy) propane as substrates. Flavanone at 0.05 mmol/kg per day for seven days increased the glucuronidation of 1-naphthol, and at 0.20 mmol/kg increased the glucuronidation of chloramphenicol. Flavanone administration did not alter sulphotransferase activity with 2-naphthol as the substrate and did not enhance glutathione-S-transferase or glucuronyltransferase activity when added in vitro.

Animals↗

PubMed1990

Purification of flavanone 3 beta-hydroxylase from Petunia hybrida: antibody preparation and characterization of a chemogenetically defined mutant.

Flavanone 3 beta-hydroxylase from Petunia hybrida has been purified to apparent homogeneity utilizing an improved purification protocol including chromatography of the partially purified enzyme on hydroxyapatite, chromatofocusing, and hydrophobic interaction chromatography on phenyl-Superose. The specificity of mouse and rabbit polyclonal antisera directed to flavanone 3 beta-hydroxylase was demonstrated by Western blotting and immunotitration with crude extracts from wild-type flowers of P. hybrida and with the purified enzyme. Cross-reactivity was observed with flavanone 3 beta-hydroxylase from extracts of illuminated parsley cells. A Petunia mutant with white flowers, previously shown to lack 3 beta-hydroxylase activity and to accumulate flavanone glycosides, showed complete absence of the enzyme protein.

Antigen-Antibody Complex↗

PubMed1996

Comparative study on the antibacterial activity of phytochemical flavanones against methicillin-resistant Staphylococcus aureus.

Differently substituted flavanones were isolated from Leguminosae and their antibacterial activity was comparatively studied against methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentrations (MICs) of phytochemical flavanones to clinical isolates of MRSA were determined by a serial agar dilution method. The structure-activity relationship has indicated that 2',4'- or 2',6'-dihydroxylation of the B ring and 5,7-dihydroxylation of the A ring in the flavanone structure are important for significant anti-MRSA activity and that substitution with a certain aliphatic group at the 6- or 8-position also enhances the activity. Among the thirteen flavanones tested, tetrahydroxyflavanones with these structural characteristics isolated from Sophora exigua and Echinosophora koreensis showed intensive activity to inhibit the growth of all MRSA strains at 3.13-6.25 micrograms/ml. The present hydroxyflavanones would be useful in the phytotherapeutic strategy against MRSA infections.

Anti-Bacterial Agents↗

PubMed1997

Cytotoxic prenylated flavanones from Monotes engleri.

From the leaves of Monotes engleri, five prenylated flavanones were isolated as constituents that displayed cytotoxic activity against several human cancer cell lines. There of these substances are novel, namely, 6-(1,1-dimethylallyl)naringenin, 6-(1,1-dimethylallyl)eriodictyol and 3'-O-methyl-6-(1,1-dimethylallyl)-eriodictyol, with the other two active substances being the known flavanones, 6,8-diprenyleriodictyol and hiravanone. Additionally, two novel, but non-cytotoxic, biogenetically related flavanones were isolated, 6-[(2RS)-hydroxy-3-methyl-3-butenyl]-8-prenyleriodictyol and 5,4'-dihydroxy-4",4"-dimethyl-5"-methyl-5"H-dihydrofurano[2",3": 6,7]flavanone. The structures of the new compounds were determined by spectral analysis 1D- and 2D-NMR experiments.

Antineoplastic Agents, Phytogenic↗

PubMedDate not supplied

Nirurin: a new prenylated flavanone glycoside from Phyllanthus nirurii.

A new prenylated flavanone glycoside, nirurin, has been isolated from Phyllanthus nirurii. On the basis of chemical and spectral studies, its structure is proposed as 5,6,7,4'-tetrahydroxy-8-(3-methylbut-2-enyl) flavanone-5-O-rutinoside (1). The aglycone, also a new flavanone, has been characterized as 5,6,7,4'-tetrahydroxy-8-(3-methylbut-2-enyl) flavanone, which may be designated as nirurinetin (2).

Acetylation↗

PubMed2002

Synthesis and aromatase inhibitory activity of flavanones.

PURPOSE: Aromatase inhibitors are known to prevent the conversion of androgens to estrogens and play a significant role in the treatment of estrogen dependent diseases such as breast cancer. Some flavonoids have been reported as potent aromatase inhibitors; therefore, in an effort to develop novel anti breast cancer agents, B ring substituted flavanones with a 7-methoxy group on A ring were synthesized and tested to assess their ability to inhibit aromatase activity and to determine the optimal B ring substitution pattern. METHODS: A series of flavanones was prepared by cyclisation of 2'-hydroxychalcones previously obtained by Claisen-Schmidt condensation and the aromatase inhibitory activity of these compounds was investigated using human placental microsomes and radiolabeled [1,2,6,7-(3)H]-androstenedione as substrate. RESULTS: Almost all flavanones exhibited inhibitory effect on the aromatase activity but their potency was dependent on their B ring substitution pattern. Hydroxylation at position 3' and/or 4' enhanced the anti-aromatase activity; thus, 3',4'-dihydroxy-7-methoxyflavanone was found to be twice more potent than aminoglutethimide, the first aromatase inhibitor clinically used. CONCLUSIONS: These results indicated that these flavanones could be considered as potential anti breast cancer agents through the inhibition of aromatase activity and allowed us to select some of these compounds as skeleton for the development of flavonoid structurally-related aromatase inhibitors.

Aromatase↗

PubMed2003

Production of plant-specific flavanones by Escherichia coli containing an artificial gene cluster.

In plants, chalcones are precursors for a large number of flavonoid-derived plant natural products and are converted to flavanones by chalcone isomerase or nonenzymatically. Chalcones are synthesized from tyrosine and phenylalanine via the phenylpropanoid pathway involving phenylalanine ammonia lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumarate:coenzyme A ligase (4CL), and chalcone synthase (CHS). For the purpose of production of flavanones in Escherichia coli, three sets of an artificial gene cluster which contained three genes of heterologous origins--PAL from the yeast Rhodotorula rubra, 4CL from the actinomycete Streptomyces coelicolor A3(2), and CHS from the licorice plant Glycyrrhiza echinata--were constructed. The constructions of the three sets were done as follows: (i) PAL, 4CL, and CHS were placed in that order under the control of the T7 promoter (P(T7)) and the ribosome-binding sequence (RBS) in the pET vector, where the initiation codons of 4CL and CHS were overlapped with the termination codons of the preceding genes; (ii) the three genes were transcribed by a single P(T7) in front of PAL, and each of the three contained the RBS at appropriate positions; and (iii) all three genes contained both P(T7) and the RBS. These pathways bypassed C4H, a cytochrome P-450 hydroxylase, because the bacterial 4CL enzyme ligated coenzyme A to both cinnamic acid and 4-coumaric acid. E. coli cells containing the gene clusters produced two flavanones, pinocembrin from phenylalanine and naringenin from tyrosine, in addition to their precursors, cinnamic acid and 4-coumaric acid. Of the three sets, the third gene cluster conferred on the host the highest ability to produce the flavanones. This is a new metabolic engineering technique for the production in bacteria of a variety of compounds of plant and animal origin.

Acyltransferases↗

PubMedDate not supplied

Anticancer potential of N,N-diethylaminoethyl ethers of flavanone oximes: a comparison with mitoxantrone action on rat Yoshida sarcoma cells in vivo.

This study was performed to evaluate the anticancer abilities of four biologically active N,N-diethylaminoethyl ethers of flavanone oximes against rat Yoshida Sarcoma cells in vivo, and to investigate the mechanism(s) involved. The effects were compared with those of anthraquinone drug (mitoxantrone) action. The presented results provide the first evidence that all the investigated substances induce programmed cell death (apoptosis) of Yoshida Sarcoma cells in vivo. On interpretative grounds, the administration of investigated flavanone derivatives in the promotion phase of the disease led to both growth inhibition (cell cycle perturbation) and apoptosis. A correlation was found between structure of the substituent(s) at B-ring of substances and the revealed anticancer activity. The data suggest that flavanone derivatives (oxime ethers) besides their antiradical, antioxidant and radioprotector properties observed before, may act as promising anticancer agents acting in the promotion phase of disease. This finding prompted us to consider the development of a new strategy: modulation of effects using combination therapy involving mitoxantrone and flavanone oximes.

Animals↗

PubMedDate not supplied

Chiral resolution of four major flavanones in post-administrative urine of Chinese herbal medicines by HPLC on macroporous silica gel coated with cellulose tris(3,5-dimethylphenylcarbamate).

Direct chiral resolution of four major flavanones recovered from post-administrative urine of the traditional Chinese medicines Daisaiko-to and Shosaiko-to was achieved by high-performance liquid chromatography (HPLC) on macroporous silica gel coated with cellulose tris(3,5-dimethylphenylcarbamate), Chiralcel OD. Chromatographic conditions were optimized so as to attain satisfactory enantiomeric resolution of the polysubstituted flavanones. Urinary liquiritigenin and naringenin were considerable mixtures of R and S-enantiomers, while S-enantiomers of dihydrowogonin and dihydrooroxylin A were predominantly excreted. Our chiral HPLC techniques can be applied to pharmacokinetical evaluation of the chiral flavanone enantiomers following oral administration of the herbal medicines.

Administration, Oral↗

PubMed2003

Heterologous production of flavanones in Escherichia coli: potential for combinatorial biosynthesis of flavonoids in bacteria.

Chalcones, the central precursor of flavonoids, are synthesized exclusively in plants from tyrosine and phenylalanine via the sequential reaction of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumarate:coenzyme A ligase (4CL) and chalcone synthase (CHS). Chalcones are converted into the corresponding flavanones by the action of chalcone isomerase (CHI), or non-enzymatically under alkaline conditions. PAL from the yeast Rhodotorula rubra, 4CL from an actinomycete Streptomyces coelicolor A3(2), and CHS from a licorice plant Glycyrrhiza echinata, assembled as artificial gene clusters in different organizations, were used for fermentation production of flavanones in Escherichia coli. Because the bacterial 4CL enzyme attaches CoA to both cinnamic acid and 4-coumaric acid, the designed biosynthetic pathway bypassed the C4H step. E. coli carrying one of the designed gene clusters produced about 450 microg naringenin/l from tyrosine and 750 microg pinocembrin/l from phenylalanine. The successful production of plant-specific flavanones in bacteria demonstrates the usefulness of combinatorial biosynthesis approaches not only for the production of various compounds of plant and animal origin but also for the construction of libraries of "unnatural" natural compounds.

Escherichia coli↗

PubMed2002

Cancer chemopreventive activity of flavanones on Epstein-Barr virus activation and two-stage mouse skin carcinogenesis.

To search for possible cancer chemopreventive agents from natural sources, we performed primary screening of ten flavanones isolated from plants belonging to Rutaceae and Leguminosae by examining their possible inhibitory effects on Epstein-Barr virus (EBV) early antigen activation induced by 12-O-tetradecanoylphorbol-13-acetate in Raji cells. All of the flavanones tested in this study showed inhibitory activity against EBV, without showing any cytotoxicity. Amorilin (3), which has three prenyl (3-methyl-2-butenyl) side-chains in the molecule, showed the most potent activity. Furthermore, lupinifolin (5) exhibited a marked inhibitory effect on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. These results indicate that some of these prenylated flavanones might be valuable as potential cancer chemopreventive agents (anti-tumor promoters).

Animals↗

PubMed2004

Changes in the levels of polymethoxyflavones and flavanones as part of the defense mechanism of Citrus sinensis (cv. Valencia Late) fruits against Phytophthora citrophthora.

Phytophthora citrophthora causes serious losses in Citrus fruits through brown rot lesion. The effect of infection with P. citrophthora on Citrus sinensis (cv. Valencia Late) fruits was studied, with particular reference to the levels of the flavanones hesperidin and isonaringin and the polymethoxyflavones sinensetin, nobiletin, tangeretin, and heptamethoxyflavone, because flavonoids are most probably involved as natural defense or resistance mechanisms in this genus. Changes in the levels of these flavonoids were detected after infection. The hesperidin and isonaringin contents fell by 13 and 67%, respectively, whereas the contents of their corresponding aglycons, hesperetin and naringenin, increased, suggesting the hydrolyzing effect of this fungus on the glycosylated flavanones. The heptamethoxyflavone, nobiletin, sinensetin, and tangeretin levels increased by 48, 28, 26, and 24%, respectively. The in vitro study revealed that these compounds acted as antifungal agents, the most active being the aglycons (naringenin and hesperetin), followed by the polymethoxyflavones and flavanone glycosides. The participation of these flavonoids in the defense mechanism of this Citrus species is discussed.

Citrus sinensis↗

PubMed2004

Separation of flavanone-7-O-glycoside diastereomers and analysis in citrus juices by multidimensional liquid chromatography coupled with mass spectrometry.

The major flavanone-7-O-glycoside constituents in citrus fruit juices (naringin, hesperidin, neohesperidin, narirutin, and eriocitrin) were separated as diastereomers by multidimensional liquid chromatography. The method consisted of coupling two HPLC columns: a reversed-phase (RP(18)) column was used for the separation of flavanone glycosides, which were, then, individually switched into a carboxymethylated beta-cyclodextrin (beta-CD)-based column and resolved as the corresponding stereoisomers. The method was used for the full analysis of flavanone glycosides in fresh hand-squeezed and commercial fruit juices by combining the quantitative estimation with the diastereomeric analysis. Quantitative data were in general consistent with previously reported data in this field. CC-LC isomer analysis was carried out by coupling the beta-CD column with a mass spectrometer operated with negative ion electrospray ionization (ESI-MS). The results showed that hesperidin was present in orange juices almost exclusively as the 2S isomer, whereas narirutin had mainly the 2R configuration. In grapefruit juices (2S)-naringin prevailed with the respect to the 2R isomer, whereas the opposite was true for narirutin. Lemon juices contained eriocitrin stereoisomers in equal amount (50% each), but hesperidin was almost exclusively found as the 2S isomer. Significant differences of the diastereomeric ratios were observed between freshly squeezed juices and juices from commercial sources.

Beverages↗

PubMed2005

Cytotoxic flavanones of Schizolaena hystrix from the Madagascar rainforest.

Bioassay-guided fractionation of an ethanol extract of a Madagascar collection of Schizolaena hystrix afforded three new flavanones, schizolaenone A (1), schizolaenone B (2), and 4'-O-methylbonannione A (3), as well as three known flavanones, nymphaeol A, bonannione A, and macarangaflavanone B, and the flavanol bonanniol A. The structures of compounds 1-3 were determined by various one- and two-dimensional NMR techniques. All of the isolates were tested for cytotoxicity against the A2780 human ovarian cancer cell line. Nymphaeol A (IC(50) = 5.5 microg/mL) exhibited the greatest cytotoxicity, while the other flavanones were found to be only weakly active.

Flavanones↗

PubMed1993

Isolation and biological effects of 7-O-methyleriodictyol, a flavanone isolated from Artemisia monosperma, on rat isolated smooth muscles.

The isolation for the first time from the genus Artemisia (Compositae) of the known flavanone, 7-O-methyleriodictyol (7-methoxy-5,3',4'-trihydroxy-flavanone), its identification, and its biological effects on rat isolated smooth muscles are described. 7-O-Methyleriodictyol (10(-7) M to 3 x 10(-4) M) caused concentration-dependent inhibition of the amplitude of the phasic contractions and reduced the tone of the ileum, the uterus, and the urinary bladder. It also caused relaxation of the phenylephrine-precontracted pulmonary artery and the acetylcholine-precontracted trachea. The flavanone also shifted to the right the acetylcholine concentration-effect curve on the ileum and the oxytocin concentration-effect curve on the uterus. The maximum contractions induced by acetylcholine or oxytocin were also inhibited by 7-O-methyleriodictyol. These antispasmodic effects are partly consistent with the use of A. monosperma in folk medicine for certain gastrointestinal disorders.

Animals↗