Showing papers on "Flavanone published in 2003"
TL;DR: The antioxidant activities of dihydrochalcones against the stable free radical (1,1-diphenyl-2-picrylhydrazyl) and lipid peroxidation in the erythrocyte membrane were systematically examined.
Abstract: Dihydrochalcones are a family of bicyclic flavonoids, defined by the presence of two benzene rings joined by a saturated three carbon bridge. In the present study, we systematically examined the antioxidant activities of dihydrochalcones against the stable free radical (1,1-diphenyl-2-picrylhydrazyl) and lipid peroxidation in the erythrocyte membrane. All dihydrochalcones exhibited higher antioxidant activities than the corresponding flavanones. The 1H NMR analysis indicated that the active dihydrochalcone has a time-averaged conformation in which the aromatic A ring is orthogonal to the carbonyl group, while the inactive dihydrochalcone such as 2‘-O-methyl-phloretin has a strongly hydrogen-bonded phenolic hydroxyl group, suggestive of a coplanar conformation. A hydroxyl group at the 2‘-position of the dihydrochalcone A ring, newly formed by reduction of the flavanone C ring, is an essential pharmacophore for its radical scavenging potential. Keywords: Antioxidant; dihydrochalcone; 1,1-diphenyl-2-picrylhy...
240 citations
TL;DR: Results showed that flavonoids and phenolic acids could be used for authenticating honey floral origins, and abscisic acid may aid in this authentication.
232 citations
TL;DR: Orange juices, particularly those rich in anthocyanins, may represent a significant dietary source of flavonoids, and a comparison of the phenolic compositions, the ascorbic acid contents and the antioxidant activities of fresh Sicilian orange juices showed a good correlation with the determined antioxidant capacity.
Abstract: Epidemiological evidence has suggested that consumption of fruit and vegetables reduces the risk of both cancer and cardiovascular diseases, potentially through the biological actions of components such as vitamin C, vitamin E, flavonoids and carotenoids. Citrus species are extremely rich sources in vitamin C and flavanones, a class of compounds which belongs to the flavonoids family. A comparison of the phenolic compositions, the ascorbic acid contents and the antioxidant activities of fresh Sicilian orange juices from pigmented (Moro, Tarocco and Sanguinello) and non-pigmented (Ovale, Valencia and Navel) varieties of orange (Citrus sinensis L. Osbeck), was undertaken. The simultaneous characterisation and quantification of the major flavanone, anthocyanin and hydroxycinnamate components were attained by HPLC with diode array detection. Differences between varieties in terms of the flavanone glycoside content, particularly hesperidin, were observed, with the Tarocco juices reporting the highest content. Furthermore, cyanidin-3-glucoside and cyanidin-3-(6"-malonyl)-glucoside were predominant in all the pigmented varieties, but their concentration was higher in the juices of the Moro variety. Quantitatively, the major antioxidant component of all juices was ascorbic acid and its concentration was significantly correlated (r = 0.74, P < 0.001) with the total antioxidant activity of the juices, determined in vitro using the ABTS radical cation decolorization assay. Similarly, hydroxycinnamates (r = 0.73, P < 0.01) and anthocyanins (r = 0.98, P < 0.001) content showed a good correlation with the determined antioxidant capacity. Therefore orange juices, particularly those rich in anthocyanins, may represent a significant dietary source of flavonoids.
105 citations
TL;DR: It is demonstrated for the first time that flavanone selectively inhibits 11β-HSD1 reductase activity, this enzyme being considered as essential for the local activation of glucocorticoids and representing a potential target for the therapeutic treatment of diabetes type 2.
102 citations
TL;DR: Activity-guided fractionation of an EtOAc-soluble extract of the leaves of Muntingia calabura collected in Peru resulted in the isolation of a flavanone with an unsubstituted B-ring, (2R,3R)-7-methoxy-3,5,8-trihydroxyflavanone (5), as well as 24 known compounds, which were mainly flavanones and flavones.
101 citations
TL;DR: In this article, the effect of high boiling point solvents on the performance of the synthesis of flavanone from benzaldehyde and 2-hydroxyacetophenone over a solid MgO catalyst was examined through kinetic and FTIR spectroscopic studies.
87 citations
TL;DR: 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.
Abstract: 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.
87 citations
TL;DR: New skeletal flavonoids, anastatins A and B, were isolated from the methanolic extract of an Egyptian medicinal herb, the whole plants of Anastatica hierochuntica, and were found to show hepatoprotective effects on D-galactosamine-induced cytotoxicity in primary cultured mouse hepatocytes.
79 citations
TL;DR: Orange juice manufactured at industrial scale was subjected to digestion under in vitro gastrointestinal conditions to evaluate the influence of individual industrial processing treatments on flavanone solubility, stability, and ability to permeate through a membrane under simulated physiological conditions.
Abstract: Orange juice manufactured at industrial scale was subjected to digestion under in vitro gastrointestinal conditions (pH, temperature, and enzyme and chemical conditions) to evaluate the influence of individual industrial processing treatments on flavanone solubility, stability, and ability to permeate through a membrane under simulated physiological conditions. Four industrial processes including squeezing, standard pasteurization, concentration, and freezing were evaluated. Hand squeezing was compared with industrial squeezing. After in vitro gastrointestinal digestion of the orange juices, the flavanones able to permeate through a dialysis membrane, and those remaining in the retentate were evaluated by HPLC as were those present in the insoluble fraction. In all of the assayed orange juices, a high content of precipitated chalcones ( approximately 70% of the total flavanones) was formed under the physiological conditions of the gastrointestinal tract. Hand squeezing provided a higher concentration of flavanones in the permeated fraction and lower transformation to chalcones than industrial squeezing. Standard pasteurization did not influence the solubility and permeability of the orange juice flavanones and chalcones. Industrial concentration did not affect the amount of flavanones able to permeate but decreased the chalcones produced. Juices produced from frozen orange juice contained considerably smaller amounts of both soluble flavanones and insoluble chalcones.
73 citations
TL;DR: The bioactive compound stability of freshly squeezed juice from oranges (Citrus sinensis, L.) that were subjected to high pressure (HP) treatment was studied by measuring flavanone content and antioxidant activity as mentioned in this paper.
Abstract: The bioactive compound stability of freshly squeezed juice from oranges (Citrus sinensis, L.) that were subjected to high-pressure (HP) treatment was studied by measuring flavanone content and antioxidant activity. High hydrostatic pressure is a food preservation method used as an alternative to heat treatments. Therefore, it is essential to assess the impact of HP on bioactive compounds, and related health-promoting attributes of orange juices. Several processes, which combine high-pressure treatment with heat treatment for various time periods, were followed: T0=fresh (without treatment), T1=100 MPa/60 °C/5 min, T2=350 MPa/30 °C/2.5 min, and T3=400 MPa/40 °C/1 min. Fresh and treated samples were kept chilled (4 °C) over 10 days. After application of HP and during the chilled period, the qualitative and quantitative determination of flavanones (naringenin and hesperetin) was achieved by HPLC. Also, the radical scavenging activity of juices was assessed by the 2,2-diphenyl-1-picrylhydrazyl stable radical. T2 and T3 treatments led to an increase in the extraction of flavanone content. Flavanone content after the 10-day chilled storage period resulted in no significant quantitative changes. Radical scavenging activity was unchanged immediately after HP treatments and over the chilled storage, except in the case of T1 treatment, where it was depleted. Thus, the tested upper range (350–450 MPa) of HP treatment of orange juice led to an increase in the extraction of flavanones. In addition, the fresh-like quality of freshly squeezed orange juice over the chilled storage period tested, in terms of potential health-promoting attributes in the juices, was retained.
70 citations
TL;DR: In this article, 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.
Abstract: 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.
TL;DR: Phytochemical analysis of the root bark of Bauhinia variegata Linn yielded a new flavanone and a new dihydrodibenzoxepin together with three known flavonoids.
TL;DR: There is no discernible transition-state stabilization in the CM reaction, and in anthropomorphic terms, each enzyme has had to do what it must to have a biologically relevant rate of reaction.
Abstract: Madicago sativa chalcone isomerase (CI) catalyzes the isomerization of chalcone to flavanone, whereas E coli chorismate mutase (CM) catalyzes the pericyclic rearrangement of chorismate to prephenate Covalent intermediates are not formed in either of the enzyme-catalyzed reactions, KM and kcat are virtually the same for both enzymes, and the rate constants (ko) for the noncatalyzed reactions in water are also the same This kinetic identity of both the enzymatic and the nonenzymatic reactions is not shared by a similarity in driving forces The efficiency (ΔGo⧧ − ΔGcat⧧) for the CI mechanism involves transition-state stabilization through general-acid catalysis and freeing of three water molecules trapped in the E·S species The contribution to lowering ΔGcat⧧ by an increase in near attack conformer (NAC) formation in E·S as compared to S in water is not so important In the CM reaction, the standard free energy for NAC formation in water is 84 kcal/mol as compared to 06 kcal/mol in E·S Because the va
TL;DR: Activity-guided fractionation of the petroleum ether and ethyl acetate extracts of the stem bark of Pongamia pinnata led to the isolation of four new flavanone derivatives, one new flavone (5), one new chalcone (6), and 13 known compounds of the flavonoid, terpenoid, and fatty acid types.
Abstract: Activity-guided fractionation of the petroleum ether and ethyl acetate extracts of the stem bark of Pongamia pinnata, using cultured Hepa 1c1c7 mouse hepatoma cells to evaluate quinone reductase (QR) inducing activity, led to the isolation of four new flavanone derivatives (1-4), one new flavone (5), one new chalcone (6), and 13 known compounds of the flavonoid, terpenoid, and fatty acid types. The structures of 1-6 were characterized on the basis of the interpretation of their spectroscopic data. The absolute stereochemistry of compounds 1-4 was determined from their CD data and by Mosher ester determination. All isolates obtained were evaluated in the quinone reductase induction assay.
TL;DR: The hydroxyflavanones, which were hydroxylated on A ring of flavanone by Aspergillus saitoi, were obtained as potent antioxidants.
Abstract: Potent antioxidative hydroxyflavanones were produced with Aspergillus saitoi from hesperidin or naringin, which are flavanone glycosides in citrus fruit with weak antioxidative activity. The hydroxyflavanone produced from hesperidin was identified as 8-hydroxyhesperetin (8-HHE), a novel substance, and those from naringin were identified as carthamidin (6-hydroxynaringenin) and isocarthamidin (8-hydroxynaringenin) by FAB-MS, 1H-NMR and 13C-NMR analyses. The antioxidative activity of these hydroxyflavanones was examined by using the free radical-scavenging system of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the methyl linoleate oxidation system. The hydroxyflavanones (8-HHE, carthamidin, and isocarthamidin) exhibited stronger activity than the flavanone glycosides (hesperidin or naringin) and their aglycones (hesperetin or naringenin). The activity of 8-HHE and isocarthamidin was comparable to that of alpha-tocopherol, and that of carthamidin was weaker than that of isocarthamidin. The hydroxyflavanones, which were hydroxylated on A ring of flavanone by Aspergillus saitoi, were obtained as potent antioxidants.
TL;DR: In vitro NO inhibitory and antiproliferative activities of the isolated compounds were also tested and the active constituents identified.
Abstract: The seeds of Alpinia blepharocalyx K. Schum. (Zingiberaceae) is used in Chinese traditional medicine for the treatment of stomach disorders. From the ether fraction of a 95% ethanolic extract, which showed hepatoprotective and antiproliferative activities, we isolated 16 novel diarylheptanoids bearing a chalcone or a flavanone moiety [calyxins A-H; epicalyxins B-D, G, and H; 6-hydroxycalyxin F; and blepharocalyxins A and B] together with seven known compounds, while the residual fraction of the ethanolic extract gave 32 novel diarylheptanoids namely, calyxins A, E-G, and I-M; epicalyxins B, F, I-K, and M; deoxycalyxin A; blepharocalyxins C-E; neocalyxins A and B; (3S,5S)- and (3S,5R)-3-hydroxy-1-(4-hydroxyphenyl)-5-methoxy-7-phenyl-6E-heptene, (3S,5S)- and (3S,5R)-3-hydroxy-1-(4-hydroxyphenyl)-5-ethoxy-7-phenyl-6E-heptene, (3S)-3-methoxy-1,7-bis(4-hydroxyphenyl)-6E-hepten-5-one, 1,7-bis(4-hydroxyphenyl)-hepta-4E,6E-dien-3-one, (3S,7R)-5,6-dehydro-1,7-bis(4-hydroxy-phenyl)-4"-de-O-methyl-centrolobine, (3S,5S,6S,7R)-5,6-dihydroxy-1,7-bis(4-hydroxyphenyl)-4"-de-O-me-thylcentrolobine, (3S,5R,6S,7R)- and (3S,5S,6R,7R)-5,6-dihydroxy-1,7-bis(4-hydroxyphenyl)-4"-de-O-methyl-centrolobine, 1,2- dihydro-bis(de-O-methyl)curcumin, and (3S,7S)-5,6-dehydro-4"-de-O-methylcentrolobine, and one known diarylheptanoid [(3S,5S)-3,5-dihydroxy-1,7-bis(4-hydroxyphenyl)heptane] together with 12 other known phenolic compounds. Moreover, in vitro NO inhibitory and antiproliferative activities of the isolated compounds were also tested and the active constituents identified.
TL;DR: Flavones, flavonols, and chalcone are the most potent inhibitors of production of TNF-alpha, while genistein isoflavone displays weak inhibition, while eriodictyol flavanone is inactive.
Abstract: Certain naturally occurring flavonoids affect immunoregulatory activities in vitro and in vivo against cytokine production. Since tumor necrosis factor (TNF)-α is one of the major inflammatory cytokines, the effects of various dietary flavonoids on TNF-α production in lipopolysaccharide (LPS)-stimulated J774.1 cells were evaluated in vitro. Flavones, flavonols, and chalcone are the most potent inhibitors of production of TNF-α. Flavanone, naringenin, anthocyanidin, pelargodinin, and cyanidin exhibit moderate inhibitory activity. In contrast, genistein isoflavone displays weak inhibition, while eriodictyol flavanone is inactive. It is clear that the double bond between carbons 2 and 3 and the ketone group at position 4 of flavonoids are necessary for potent inhibitory effect. The difference in inhibitory action appears to depend on the categorized subclass of flavonoids.
TL;DR: Nine known inactive compounds and a new rotenoid were isolated from an ethyl acetate-soluble extract of the stems of Tephrosia toxicaria using a bioassay based on the induction of quinone reductase (QR) in cultured Hepa 1c1c7 mouse hepatoma cells to monitor chromatographic fractionation.
Abstract: A new butenylflavanone, (2S)-5-hydroxy-7-methoxy-8-[(E)-3-oxo-1-butenyl]flavanone (1), and a new rotenoid, 4‘,5‘-dihydro-11,5‘-dihydroxy-4‘-methoxytephrosin (2), as well as three active flavonoids of previously known structure, isoliquiritigenin (3), genistein (4), and chrysoeriol (5), along with nine known inactive compounds, α-toxicarol (6), sumatrol, 6a,12a-dehydro-α-toxicarol, 11-hydroxytephrosin, obovatin, marmesin, lupenone, benzyl benzoate, and benzyl trans-cinnamate, were isolated from an ethyl acetate-soluble extract of the stems of Tephrosia toxicaria, using a bioassay based on the induction of quinone reductase (QR) in cultured Hepa 1c1c7 mouse hepatoma cells to monitor chromatographic fractionation. The structures of compounds 1 and 2 were elucidated by spectroscopic data interpretation. All isolates were evaluated for their potential cancer chemopreventive properties utilizing an in vitro assay to determine quinone reductase induction. Selected compounds were tested in a mouse mammary organ c...
TL;DR: Three new diterpenoids, excoecarins V1-V3 (1-3) and a new flavanone glycoside (7) were isolated from the fresh stem of Excoecaria agallocha L.
Abstract: Three new diterpenoids, excoecarins V1-V3 (1-3) and a new flavanone glycoside (7) were isolated from the fresh stem of Excoecaria agallocha L. Their structures were elucidated as: 2alpha,3alpha,18-trihydroxy-3beta,20-epoxybeyer-15-ene (1), ent-2,3-secokaur-16-en-2,3-dioic acid (2), ent-3,4-seco-16alpha-hydroxyatis-4(19)-en-3-oic acid (3), and 3,5,7,3',5'-pentahydroxy-2R,3R-flavanonol 3-O-alpha-L-rhamnopyranoside (7) on the basis of spectroscopic data, chemical evidence, and/or X-ray analysis.
TL;DR: MEKC appeared to be a suitable and efficient analytical tool to follow enantiomeric composition of flavanones and the suggestion that interaction of sugar moiety of glycosides with SCh micelles give rise to chiral recognition.
Abstract: Micellar electrokinetic chromatography (MEKC) was applied for enantioseparation of selected flavanones, including naringin, hesperidin, neohesperidin, naringenin, hesperetin, pinostrobin, isosakuranetin, eriodictyol, and homoeriodictyol. gamma-Cyclodextrin (gamma-CD) and sodium cholate (SCh) were used as chiral modifiers inducing enantioselectivity to the background electrolyte. From among many investigated selectors only these two appeared to possess the best enantioselective properties in respect to studied flavanones. The mechanisms of their action are a little different; SCh used above critical micelle point concentration forms chiral micelles itself while gamma-CD is deprived of this property and requires addition of surfactants as, e.g., sodium dodecyl sulfate. It was found that SCh enables separation of flavanone glycosides diastereomers while separation of enantiomers of flavanone aglycones may be achieved with gamma-CD. Consideration of structural relation led to the suggestion that interaction of sugar moiety of glycosides with SCh micelles give rise to chiral recognition. MEKC appeared to be a suitable and efficient analytical tool to follow enantiomeric composition of flavanones.
TL;DR: Hispidone, a new flavanone, has been isolated from Onosma hispida and assigned the structure (2S)-5,2'-dihydroxy-7,4',5'-trimethoxyflavanone by spectroscopic methods.
Abstract: Hispidone, a new flavanone, has been isolated from Onosma hispida and assigned the structure (2S)-5,2'-dihydroxy-7,4',5'-trimethoxyflavanone (1) by spectroscopic methods. In addition, (2S)-5,2'-dihydroxy-7,5'-dimethoxyflavanone (2), benzoic acid (3), and 4-hydroxy benzoic acid (4) are also reported for the first time from this species.
TL;DR: Muscanone was identified as 3-O-(1", 8",14"-trimethylhexadecanyl)naringenin and was found to be active against Candida albicans and the isolation, structure elucidation, NMR spectral assignments, and bioactivities of 1 and 2 are reported.
TL;DR: The Pinus species stood out for their less diverse content of flavonoids at this stage of development compared to Picea and Abies, together with the relative abundances of the compounds within each species.
TL;DR: It is suggested that BCPCF efflux is mainly due to MRP1 activity, and flavonoid molecular structure provides a promising base for development of potent MRP 1 inhibitors.
Abstract: 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.
TL;DR: Five prenylated flavonoids were isolated from the roots of Moghania philippinensis and the structures of these compounds were determined on the basis of spectroscopic and chemical means.
TL;DR: The comparative photostability of curcumin 1, and two non-phenolicCurcuminoids: 1,7-diphenyl-1,6-heptadiene-3,5-dione 2 and dimethylcurcumin 3 in non-degassed dilute solutions has been established by UV-visible absorption spectroscopy; disappearance quantum yields were measured.
Abstract: The comparative photostability of curcumin 1, and two non-phenolic curcuminoids: 1,7-diphenyl-1,6-heptadiene-3,5-dione 2 (unsubstituted curcumin) and dimethylcurcumin 3 in non-degassed dilute solutions (approximately 3-5 x 10(-5) mol l(-1)) has been established by UV-visible absorption spectroscopy; disappearance quantum yields were measured. The similar behavior of the three studied curcuminoids is indicative of only a moderate role of phenol groups in the photodegradation process. Structural analysis of the photodegradation products of compound 2 in more concentrated solution (approximately 3.6 x 10(-3) mol l(-1)) shows formation of benzaldehyde, cinnamaldehyde, 2'-hydroxy-5',6'-benzochalcone 4, flavanone 5 and some other unidentified photoproducts. Flavanone 5 is formed by irradiation of chalcone 4. It represents a unique example of photochemical conversion of a diarylheptanoid molecule into a flavonoid, another very important class of natural products.
TL;DR: The biotransformation of flavone and flavanone proceeded very efficiently; 1 mM of each of the substrate was almost completely converted to the corresponding di- or mono-hydroxy form in 24 h.
Abstract: The bphA1(2072)A2A3A4 gene cluster codes for a shuffled biphenyl dioxygenase holoenzyme with broad substrate specificity. The bphA1(2072) encoding the large subunit of an iron–sulfur protein is a hybrid gene generated by DNA shuffling using bphA1 of Pseudomonas pseudoalcaligenes KF707 and bphA1 of Burkholderia cepacia LB400. The bphA2 encoding the small subunit of an iron–sulfur protein, bphA3 encoding a ferredoxin and bphA4 encoding a ferredoxin reductase are from P. pseudoalcaligenes KF707. The bphA1(2072)A2A3A4 gene cluster was positioned downstream of a thiostrepton-inducible promoter PtipA on a high-copy-number vector pIJ6021, and introduced into the Gram-positive, soil-inhabiting, filamentous bacterium Streptomyces lividans. Biotransformation of some flavonoids by the recombinant S. lividans cells was examined and the products were determined by EI-MS, 1 H and 13 C NMR. Flavone was converted into two products, 2′,3′-dihydroxyflavone (a major product) and 3′-hydroxyflavone (a minor product). Flavanone was converted into three products, 2′,3′-dihydroxyflavanone (a major product), 2′-hydroxyflavanone and 3′-hydroxyflavanone (minor products). 2′,3′-Dihydroxyflavanone was a novel compound. The biotransformation of flavone and flavanone proceeded very efficiently; 1 mM of each of the substrate was almost completely converted to the corresponding di- or mono-hydroxy form in 24 h. Furthermore, 6-hydroxyflavone and 6-hydroxyflavanone were also converted into 2′,6-dihydroxyflavone and 3′,6-dihydroxyflavanone, respectively. Among these products, 2′,3′-dihydroxyflavone and 2′,3′-dihydroxyflavanone showed free radical-scavenging activity.
TL;DR: Chiral separation of major flavanones in sweet orange, mandarine and grapefruit juices raised more difficulties than in lemon and sour orange juices as narirutin will not readily build complexes with most CDs.
Abstract: The 2S- and 2R-diastereomers of major flavanone-7-O-glycosides found in sweet orange (Citrus sinensis), mandarine (Citrus deliciosa), grapefruit (Citrus paradisi), lemon (Citrus limon), and sour or bitter orange juice (Citrus aurantium) were separated for the first time by chiral capillary electrophoresis (CE) employing various buffers with combined chiral selectors. Native cyclodextrins (CDs), neutral and charged CD derivatives were examined as chiral additives to the background electrolyte (BGE). Separation efficiency has not proved satisfactory with one single CD as chiral selector in the buffer, a full and simultaneos separation could often be achieved only by using combined buffer with two different CDs. Chiral separation of major flavanones in sweet orange, mandarine and grapefruit juices raised more difficulties than in lemon and sour orange juices as narirutin will not readily build complexes with most CDs. Diastereomeric flavanones of mature and immature grapefruits were compared and some differences were found: naringin showed different diastereomeric ratio and 2S-prunin appeared only in immature grapefruit. Marmalade was also examined by chiral CE. Its major flavanones corresponded to flavanone pattern of mixed sour and sweet oranges.
TL;DR: Assay-guided fractionation of the ethanol extract of the twigs and leaves of Miconia trailii yielded two new flavanone glycosides, matteucinol and farrerol, and the structures of 1-8 were elucidated by spectroscopic methods, including 2D NMR.
Abstract: Assay-guided fractionation of the ethanol extract of the twigs and leaves of Miconia trailii yielded two new flavanone glycosides, matteucinol 7-O-α-l-arabinopyranosyl(1→6)-β-d-glucopyranoside (miconioside A, 1) and farrerol 7-O-β-d-apiofuranosyl(1→6)-β-d-glucopyranoside (miconioside B, 2), along with the known compounds matteucinol 7-O-β-d-apiofuranosyl(1→6)-β-d-glucopyranoside (3), matteucinol (4), 2α,3β,19α-trihydroxyolean-12-ene-24,28-dioic acid (bartogenic acid, 5), 2α,3β,23-trihydroxyolean-12-ene-28-oic acid (arjunolic acid, 6), 2α,3α,19α, 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.
TL;DR: In this paper, a method was developed for the separation of diastereomers of flavanone-7-O-glycosides by capillary electrophoresis using sulfobutyl ether-β-cyclodextrin in the background electrolyte.
Abstract: A method was developed for the separation of diastereomers of flavanone-7-O-glycosides by capillary electrophoresis using sulfobutyl ether-β-cyclodextrin (SBE-β-CD) in the background electrolyte. The effect of the concentration of the CD additive, buffer pH, and organic modifier on the migration times and resolution for five flavanone glycosides (naringin, hesperidin, neohesperidin, narirutin, and eriocitrin) was studied. Baseline separations of these compounds as pairs of diastereoisomers were achieved with 20 mM tetraborate buffer at pH 7 containing 5 mg/mL of SBE-β-CD and 10% (v/v) of methanol. The developed method was used for the qualitative analysis of the diastereomeric composition of the major flavanone glycosides in different citrus juices. The ability of SBE-β-CD to discriminate flavanone enantiomers was also investigated.