- A new approach towards acid catalysts with high reactivity based on graphene nanosheets
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Solid acid catalysts of graphene oxide and sulfonated graphene oxide nanosheets have been prepared by using the modified Hummers and sulfonation methods. Physical characterization indicated that a number of functional groups such as -COOH, -OH, -O-, and -SO3H were introduced onto the surfaces of the as-synthesized nanosheets. The catalytic performance of the synthesized catalysts was evaluated in the hydrolysis of the glycosidic bond and Fischer esterification. The experimental results indicated that the catalytic activity of the sulfonated graphene oxide was superior to that of other solid acid catalysts with the same or higher acid strength and has also exceeded that of H2SO4 with 9.1 times of acid strength than that of the sulfonated graphene oxide. The high reactivity can be ascribed to the formation of hydrophobic cavities through the combination of graphene sheet and the oxygen-containing groups on its surface, which may facilitate the catalyst to anchor with reactants and promote the attack of protons.
- Wei, Zuojun,Yang, Yao,Hou, Yaxin,Liu, Yingxin,He, Xiaodong,Deng, Shuguang
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- Regioselective hydroxylation of diverse flavonoids by an aromatic peroxygenase
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Aromatic peroxygenases are extracellular fungal biocatalysts that selectively oxidize a variety of organic compounds. We found that the peroxygenase of the fungus Agrocybe aegerita (AaeAPO) catalyzes the H 2O2-dependent hydroxylation of diverse flavonoids. The reactions proceeded rapidly and regioselectively yielding preferentially monohydroxylated products, e.g., from flavanone, apigenin, luteolin, flavone as well as daidzein, quercetin, kaempferol, and genistein. In addition to hydroxylation, O-demethylation of fully methoxylated tangeretin was catalyzed by AaeAPO. The enzyme was merely lacking activity on the quercetin glycoside rutin, maybe due to sterical hindrance by the bulky sugar substituents. Mechanistic studies indicated the presence of epoxide intermediates during hydroxylation and incorporation of H2O2-derived oxygen into the reaction products. Our results raise the possibility that fungal peroxygenases may be useful for versatile, cost-effective, and scalable syntheses of flavonoid metabolites.
- Barková, Kate?ina,Kinne, Matthias,Ullrich, René,Hennig, Lothar,Fuchs, Annett,Hofrichter, Martin
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- Production of ortho-hydroxydaidzein derivatives by a recombinant strain of Pichia pastoris harboring a cytochrome P450 fusion gene
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CYP57B3 from Aspergillus oryzae was recently discovered to catalyze the ortho-hydroxylation of the soyisoflavone genistein. In the present study, the gene encoding CYP57B3 was fused with the reductase domain of the CYP102A1 gene (BM3R) from Bacillus megaterium, and recombinant Pichia pastoris harboring the P450 fusion gene was evaluated for its ability to produce ortho-hydroxydaidzein derivatives from daidzein. The results showed that 8-hydroxydaidzein (8-OHDe), 3′-hydroxydaidzein (3′-OHDe), and 6-hydroxydaidzein (6-OHDe) were produced during fermentation with a maximal conversion of 2.4, 0.9, and 36.3%, respectively. The maximal yield of 6-OHDe by the recombinant strain was 9.1 mg/l. To our knowledge, both the maximal yield and the conversion efficiency of 6-OHDe from daidzein in the present study are the highest among those reported in the literatures to date. The present study is also the first to demonstrate production of ortho-hydroxydaidzein derivatives using a fusion fungus cytochrome P450 enzyme.
- Chang, Te-Sheng,Chao, Shih-Yu,Chen, Yu-Cheng
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- Enzymatic studies of isoflavonoids as selective and potent inhibitors of human leukocyte 5-lipo-oxygenase
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Continuing our search to find more potent and selective 5-LOX inhibitors, we present now the enzymatic evaluation of seventeen isoflavones (IR) and nine isoflavans (HIR), and their in vitro and in cellulo potency against human leukocyte 5-LOX. Of the 26 compounds tested, 10 isoflavones and 9 isoflavans possessed micromolar potency, but only three were selective against 5-LOX (IR-2, HIR-303, and HIR-309), with IC50 values at least 10 times lower than those of 12-LOX, 15-LOX-1, and 15-LOX-2. Of these three, IR-2 (6,7-dihydroxy-4-methoxy-isoflavone, known as texasin) was the most selective 5-LOX inhibitor, with over 80-fold potency difference compared with other isozymes; Steered Molecular Dynamics (SMD) studies supported these findings. The presence of the catechol group on ring A (6,7-dihydroxy versus 7,8-dihydroxy) correlated with their biological activity, but the reduction of ring C, converting the isoflavones to isoflavans, and the substituent positions on ring B did not affect their potency against 5-LOX. Two of the most potent/selective inhibitors (HIR-303 and HIR-309) were reductive inhibitors and were potent against 5-LOX in human whole blood, indicating that isoflavans can be potent and selective inhibitors against human leukocyte 5-LOX in vitro and in cellulo. Of the 26 compounds tested, 10 isoflavones and 9 isoflavans possessed micromolar potency, but only three were selective against 5-LOX (IR-2, HIR-303, and HIR-309), with IC50 values at least 10 times lower than those of 12-LOX, 15-LOX-1, and 15-LOX-2. Docking and steered molecular dynamics were performed to determinate the structure-activity relationship.
- Mascayano, Carolina,Espinosa, Victoria,Sepúlveda-Boza, Silvia,Hoobler, Eric K.,Perry, Steve,Diaz, Giovanni,Holman, Theodore R.
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p. 894 - 901
(2015/06/23)
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- Free-radical-scavenging, antityrosinase, and cellular melanogenesis inhibitory activities of synthetic isoflavones
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In this study, we examined the potential of synthetic isoflavones for application in cosmeceuticals. Twenty-five isoflavones were synthesized and their capacities of free-radical-scavenging and mushroom tyrosinase inhibition, as well as their impact on cell viability of B16F10 murine melanoma cells and HaCaT human keratinocytes were evaluated. Isoflavones that showed significant mushroom tyrosinase inhibitory activities were further studied on reduction of cellular melanin formation and antityrosinase activities in B16F10 melanocytes in vitro. Among the isoflavones tested, 6-hydroxydaidzein (2) was the strongest scavenger of both ABTS.+ and DPPH. radicals with SC50 values of 11.3±0.3 and 9.4±0.1 μM, respectively. Texasin (20) exhibited the most potent inhibition of mushroom tyrosinase (IC50 14.9±4.5 μM), whereas retusin (17) showed the most efficient inhibition both of cellular melanin formation and antityrosinase activity in B16F10 melanocytes, respectively. In summary, both retusin (17) and texasin (20) exhibited potent free-radical-scavenging capacities as well as efficient inhibition of cellular melanogenesis, suggesting that they are valuable hit compounds with potential for advanced cosmeceutical development.
- Lu, Tzy-Ming,Ko, Horng-Huey,Ng, Lean-Teik,Hsieh, Yen-Pin
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p. 963 - 979
(2015/06/25)
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- Facile method for the large-scale synthesis of 6,7,4′-trihydroxyisoflavanone
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6,7,4′-Trihydroxyisoflavanone, the main source of which is extracted from soybeans, has been found to have diverse significant bioactivities. A large-scale, cost-effective, and facile chemical synthesis of 6,7,4′-trihydroxyisoflavanone is presented herein. Its synthesis is characterized by three steps with an overall yield of 71% and a purity or more than 99.0%. This reaction can be scaled up to multikilogram quantities, providing a solid basis for its further bioactivity studies and drug development. With this same method, 6,7,3′,4′-tetrahydroxyisoflavanone, an analog of 6,7,4′-trihydroxyisoflavanone, also can be largely prepared, indicating this modified synthetic method is potentially available for large-scale synthesis of a broad range of multihydroxyl isoflavanones.
- Liu, Jing,Yang, Zhangyou,Luo, Shenglin,Hao, Yuhui,Ren, Jiong,Su, Yongping,Wang, Weidong,Li, Rong
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p. 3296 - 3303
(2015/10/12)
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- Inhibitors for expression of IgE receptor on human mast cell from Puerariae Flos
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Bioassay-guided separation of the extract of the medicinal plant, Puerariae Flos, disclosed the two isoflavones tectorigenin (1) and genistein (2) as the inhibitors for expression of IgE receptor (FcRI), the key molecule triggering the allergic reactions, on human mast cells. As a result of analysis of structure-activity relationship of the naturally occurring and synthesized isoflavones, 7-O-methyl glycitein (11) was disclosed as the more potent inhibitor than tectorigenin (1). These isoflavone ingredients suppressed expression of FcRI more potently than the active flavonoids found previously. In addition, tectorigenin (1) was clarified to particularly reduce generation of γ-chain subunit to suppress expression of FcRI among the three subunits.
- Tamura, Satoru,Yoshihira, Kunichika,Tokumaru, Mariko,Zisheng, Xu,Murakami, Nobutoshi
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scheme or table
p. 3872 - 3875
(2010/08/19)
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- Synthesis of various kinds of isoflavones, isoflavanes, and biphenyl- ketones and their 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activities
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Forty-eight kinds of isoflavones (8), thirty-one isoflavanes (9), and forty-seven biphenyl-ketones (10, 10') were synthesized from eleven kinds of substituted phenols (11) and six phenylacetic acids (12). Among them, seventy-five compounds are new. The radical scavenging activities of these compounds were evaluated using 1,1- diphenyl-2-picrylhydrazyl (DPPH) at pH 6.0. We found that thirty-nine out of forty-three compounds having a catechol moiety on either the A- or the B-ring exhibited a high activity (ED50=12-54 μM) similar to that of catechin. In these cases, the remaining part of their structure seemed to have little effect on their activity. Many 6- or 8-hydroxyisoflavanes (9E-I) and their biphenyl-ketone derivatives (10E-H) also showed a high activity (ED50=50=26-32 μM). This study suggests that natural isoflavones have the possibilities of exhibiting antioxidant activities through the hydroxylation at the C6-, C8-, or C3'-position or the formation of the isoflavanes (9) and/or the biphenyl-ketone derivatives (10') by metabolism or biotransformation.
- Goto, Hideyuki,Terao, Yoshiyasu,Akai, Shuji
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experimental part
p. 346 - 360
(2009/12/27)
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- 7-Hydroxy-benzopyran-4-one derivatives: A novel pharmacophore of peroxisome proliferator-activated receptor α and -γ (PPARα and γ) dual agonists
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Design, synthesis, and in vitro bioevaluation of a new class of potential dual PPARα and γ agonists discovered through a structure-driven design paradigm are described. The 7-hydroxy-benzopyran-4-one moiety (includes flavones, flavanones, and isoflavones) is the key pharmacophore of these novel molecules, exhibiting similarity to the core structure of both fibrates and thiazolidinediones. New lead PPAR ligands were identified from "natraceuticals" and synthetic analogues. In total, 77 molecules, including chalcones, flavones, flavanones, isoflavones, and pyrazole derivatives, were screened and structure-activity relationship studies of the dual agonists undertaken. Compounds 68, 70, 72, and 76 were identified as novel and potent dual PPARα and γ agonists. These novel molecules may have the potential to be the future leads in PPAR-related disorders, including type II diabetes mellitus and metabolic syndrome. 2009 American Chemical Society.
- Matin, Azadeh,Gavande, Navnath,Kim, Moon S.,Yang, Nancy X.,Salam, Noeris K.,Hanrahan, Jane R.,Roubin, Rebecca H.,Hibbs, David E.
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experimental part
p. 6835 - 6850
(2010/04/04)
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- Structure-activity relationship studies of flavonoids as potent inhibitors of human platelet 12-hLO, reticulocyte 15-hLO-1, and prostate epithelial 15-hLO-2
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Human lipoxygenase (hLO) isozymes have been implicated in a number of disease states and have attracted much attention with respect to their inhibition. One class of inhibitors, the flavonoids, have been shown to be potent lipoxygenase inhibitors but their study has been restricted to those compounds found in nature, which have limited structural variability. We have therefore carried out a comprehensive study to determine the structural requirements for flavonoid potency and selectivity against platelet 12-hLO, reticulocyte 15-hLO-1, and prostate epithelial 15-hLO-2. We conclude from this study that catechols are essential for high potency, that isoflavones and isoflavanones tend to select against 12-hLO, that isoflavans tend to select against 15-hLO-1, but few flavonoids target 15-hLO-2.
- Vasquez-Martinez, Yesseny,Ohri, Rachana V.,Kenyon, Victor,Holman, Theodore R.,Sepulveda-Boza, Silvia
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p. 7408 - 7425
(2008/09/18)
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- Isoflavone metabolites
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There are disclosed compounds of formulae (I) or (II) in which A is selected from the group consisting of (1), (2), (3) and (4);OH, and one of R1 and R2 is selected from H, OH and OCH3, and the other of R1 and R
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