- CONVERSION OF EMODIN TO CHRYSOPHANOL IN A CELL-FREE SYSTEM FROM PYRENOCHAETA TERRESTRIS
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Incubation of a cell-free extract from Pyrenochaeta terrestris with emodin gave a single major product which was purified and identified as chrysophanol by mass spectrometry.Maximum conversion of emodin to chrysophanol was obtained with anaerobic conditions and NADPH, ATP, mercaptoethanol, iron(II) and glycerol.The apparent Km for emodin in the crude extract was 1.0 +/- 0.2 μM.At 4.2 μM, the conversion of emodin was 17 times the conversion of emodinanthrone to chrysophanol plus chrysophanolanthrone.It is proposed that chrysophanol is synthesized in plant and fungal species primarily by dehydroxylation of emodin.Key Word Index-Pyrenochaeta terrestris; Sphaeropsidaceae; cell-free system; biosynthesis; emodin; chrysophanol
- Anderson, John A.
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- In vitro formation of the anthranoid scaffold by cell-free extracts from yeast-extract-treated Cassia bicapsularis cell cultures
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The anthranoid skeleton is believed to be formed by octaketide synthase (OKS), a member of the type III polyketide synthase (PKS) superfamily. Recombinant OKSs catalyze stepwise condensation of eight acetyl units to form a linear octaketide intermediate which, however, is incorrectly folded and cyclized to give the shunt products SEK4 and SEK4b. Here we report in vitro formation of the anthranoid scaffold by cell-free extracts from yeast-extract-treated Cassia bicapsularis cell cultures. Unlike field- and in vitro-grown shoots which accumulate anthraquinones, cell cultures mainly contained tetrahydroanthracenes, formation of which was increased 2.5-fold by the addition of yeast extract. The elicitor-stimulated accumulation of tetrahydroanthracenes was preceded by an approx. 35-fold increase in OKS activity. Incubation of cell-free extracts from yeast-extract-treated cell cultures with acetyl-CoA and [2-14C]malonyl-CoA led to formation of torosachrysone (tetrahydroanthracene) and emodin anthrone, beside two yet unidentified products. No product formation occurred in the absence of acetyl-CoA as starter substrate. To confirm the identities of the enzymatic products, cell-free extracts were incubated with acetyl-CoA and [U- 13C3]malonyl-CoA and 13C incorporation was analyzed by ESI-MS/MS. Detection of anthranoid biosynthesis in cell-free extracts indicates in vitro cooperation of OKS with a yet unidentified factor or enzyme for octaketide cyclization.
- Abdel-Rahman, Iman A.M.,Beuerle, Till,Ernst, Ludger,Abdel-Baky, Afaf M.,Desoky, Ezz El-Din K.,Ahmed, Amany S.,Beerhues, Ludger
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- A Biomimetic Synthesis of Racemic Dihydroanthracen-1(2H)-ones Using Sodium Borohydride in Water
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Herein, we report a single step synthesis of racemic dihydroanthracenones by the reduction of anthraquinones using NaBH4 and Na2S2O4 in water. The racemic mixture is utilized to determine the enantiomeric excess for the chiral dihydroanthracenones reportedly synthesized by the chemoenzymatic reduction of anthraquinones. The results show > 99percent ee for the putative biosynthetic intermediates, (R)-configured dihydroanthracenones obtained through chemoenzymatic reduction of emodin, lunatin, and citreorosein using MdpC of Aspergillus nidulans or PHAR of Cochliobolus lunatus. This also implied for the confirmation about the optical purity of the natural products which are synthesized using chiral dihydroanthracenones.
- Mondal, Amit,Singh, Shailesh Kumar,Saha, Nirmal,Husain, Syed Masood
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- PURIFICATION AND PROPERTIES OF EMODIN DEOXYGENASE FROM PYRENOCHAETA TERRESTRIS
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Emodin deoxygenase, which catalyses the reduction of emodin to chrysophanol, was purified 17-fold from crude extracts of Pyrenochaeta terrestris.The Mr of the enzyme was 103000.Upward curvature was exhibited by the plot of rate vs concentration of the crude extract.The protein fraction obtained from gel filtration with Sephadex G-75 was activated by ATP plus a low Mr fraction; ATP alone or low Mr fraction alone did not increase its activity.The Km for NADPH of the crude extract was 3 μM, that after NADPH gel filtration of the crude extract was 1.5 mM.It is proposed that ATP plus an unidentified factor increase emodin deoxygenase activity by lowering the Km for NADPH.Iron II, which increased activity of the crude extract, inhibited activity of the partially purified enzyme by 95 percent.Sulphydryl reagents inhibited activity by 90 percent.Partially purified emodin deoxygenase activity was low in the absence of mercaptans and was increased eight-fold by the addition of dithiothreitol.It is proposed that a pair of thiol groups is required for activity and that they occur in the disulphide form in the absence of mercaptans.
- Anderson, John A.,Lin, Bor-Kang,Wang, Shan Shue
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- NADPD ISOTOPE EFFECT ON ACTIVITY OF EMODIN DEOXYGENASE
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Thermoanaerobium brokii alcohol dehydrogenase catalysed the transfer of the pro 4H, hydrogen of NADPH.The effect of 4-deuteration of NADPH on the initial rate of conversion of emodin to chrysophanol catalysed by emodin deoxygenase was determined.The deuterium isotope effects on V/Km and Vmax with NADPH were 1.20 +/- 0.36 and 1.10 +/- 0.11, respectively.The deuterium isotope effects on V/Km and Vmax with NADPH were 4.08 +/- 1.55 and 6.90 +/- 0.74, respectively.Emodin deoxygenase, therefore, transfers the 4S hydrogen of NADPD in the rate-determining step.Key word index - Pyrenochaeta terrestris; Sphaeropsidaceae; emodin; chrysophanol; deoxygenase; 2>NADPH; kinetics.
- Anderson, John A.,Lin, Bor-Kang
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- Predomination of dimers over naturally occurring anthraquinones in soil
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Four bianthraquinones and two monoanthraquinones were isolated as the major soil anthraquinones from a volcanic ash soil in Japan. They were identified as a new natural product 5,5'-biphyscion (named hinakurin) (3) and five known compounds, chrysotalunin (1), (-)-7,7'-biphyscion (2), microcarpin (4), chrysophanol (5), and physcion (6) using MS, 1D NMR, and 2D NMR techniques. Although the dimers (1-4) are rarely found as natural products, they, along with 5 and 6, were ubiquitous and predominant over other anthraquinones in various soils from Japan and Nepal.
- Fujitake, Nobuhide,Suzuki, Takeshi,Fukumoto, Mariko,Oji, Yoshikiyo
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- (R)-PRECHRYSOPHANOL FROM ALOE GRAMINICOLA
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From the subterranean stem of Aloe graminicola, a new pre-anthraquinone named prechrysophanol was isolated.Chrysophanol, helminthosporin, (R)-aloesaponol II, aloesaponarin I, aloesaponarin II and laccaic acid D methyl ester were also identified.
- Yenesew, Abiy,Ogur, J. A.,Duddeck, H.
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- Synthetic Studies of the Rubellin Natural Products: Development of a Stereoselective Strategy and Total Synthesis of (+)-Rubellin C
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This manuscript describes our studies of the class of natural products known as the rubellins, culminating in the total synthesis of (+)-rubellin C. These anthraquinone-based natural products contain a variety of stereochemical and architectural motifs, including a 6-5-6-fused ring system, 5 stereogenic centers, and a central quaternary center. Herein, we report our development of a strategy to target the stereochemically dense core and anthraquinone nucleus, including approaches such as a bifunctional allylboron and vinyl triflate reagent, an anthraquinone benzylic metalation strategy, and a late-stage anthraquinone introduction strategy. Our studies culminate in a successful route to highly functionalized anthraquinone-based natural product scaffolds and a stereoselective total synthesis of (+)-rubellin C. These strategies and outcomes will aid in synthetic planning toward anthraquinone-based natural products of high interest.
- Gartman, Jackson A.,Tambar, Uttam K.
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p. 11237 - 11262
(2021/08/16)
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- Promiscuity of an unrelated anthrol reductase ofTalaromyces islandicusWF-38-12
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An anthrol reductase ofTalaromyces islandicusWF-38-12 (ARti-2) from an unrelated biosynthetic gene cluster (BGC) has been identified and characterized. It catalyses the NADPH-dependent reduction of anthrols (hydroanthraquinones), estrone and a naphthol with high stereo- and regioselectivity. The role of ARti-2, theCRG89872.1gene of the same BGC and non-enzymatic oxidation in the biosynthesis of (?)-flavoskyrin has been proposed.
- Singh, Shailesh Kumar,Rajput, Anshul,De, Arijit,Chakraborti, Tapati,Husain, Syed Masood
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p. 474 - 478
(2021/02/09)
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- Synthesis of (-)-Flavoskyrins by Catalyst-Free Oxidation of (R)-Configured Dihydroanthracenones in Aqueous Media and Its (Bio)synthetic Implications
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A catalyst-free method for the synthesis of dimeric (-)-flavoskyrins has been developed. It involves the autoxidation of chemoenzymatically synthesized (R)-configured dihydroanthracenones in the presence of molecular oxygen in buffer of pH 6.0 followed by spontaneous [4 + 2] cycloaddition in stereocontrolled exo-anti fashion to form (-)-flavoskyrins. The method is applied to obtain several homo- A s well as heterodimerized flavoskyrins (nine examples) in 27-72% yield and implies the involvement of a similar pathway in the (bio)synthesis of modified bisanthraquinones and their analogues.
- Mondal, Amit,De, Arijit,Husain, Syed Masood
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supporting information
p. 8511 - 8515
(2020/11/12)
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- Chemoenzymatic, biomimetic total synthesis of (-)-rugulosin B, C and rugulin analogues and their biosynthetic implications
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Herein, we report the chemoenzymatic synthesis of a heterodimeric (-)-rugulosin B, homodimeric (-)-rugulosin C, and several rugulin analogues in three to four steps starting from anthraquinones. This work supports dimerization between variously substituted putative monomeric intermediates during the biosynthesis of naturally occurring (+)-rugulosin B and C.
- Mondal, Amit,Singh, Shailesh Kumar,Manna, Tanaya,Husain, Syed Masood
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supporting information
p. 3337 - 3340
(2020/04/02)
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- Synthetic process of rhein
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The invention relates to a synthetic process of rhein. The synthetic process comprises the steps of: adopting 2,3-dimethyl phenol as a raw material, performing methylation and oxidation to obtain 3-methoxy phthalic acid, performing dehydration by using acetic anhydride to obtain acid anhydride, then performing a Friedel-Crafts reaction between the obtained acid anhydride and excess methyl anisoleunder the action of aluminum trichloride to obtain the product, and then conducting cyclization by using sulfuric acid to obtain an intermediate chrysophanol, performing acetylation on the obtained chrysophanol, performing oxidation to obtain diacerein, and finally carrying out deacetylation to synthesize rhein.
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Paragraph 0019; 0024
(2018/03/07)
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- Monomeric Dihydroanthraquinones: A Chemoenzymatic Approach and its (Bio)synthetic Implications for Bisanthraquinones
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Modified bisanthraquinones are complex dimeric natural products containing a cage-like structural motif. For their biosynthesis, monomeric dihydroanthraquinones have been proposed as key intermediates despite not being isolated from natural sources or synthesized as of yet. Here, isolation and characterization of dihydroemodin, as well as dihydrolunatin, synthesized by a biomimetic and chemoenzymatic approach using NADPH-dependent polyhydroxyanthracence reductase (PHAR) from Cochliobolus lunatus followed by Pb(OAc)4 oxidation is reported. Subsequent dimerization through a hetero-Diels–Alder reaction of the dihydroemodin and dihydrolunatin resulted in (?)-flavoskyrin (68 %) and (?)-lunaskyrin (62 %), respectively. Pyridine treatment of (?)-flavoskyrin and (?)-lunaskyrin gave (?)-rugulosin and (?)-2,2′-epi-cytoskyrin A in 64 % and 60 % yield, respectively, through a cascade that involves two dimeric intermediates. Implications of the described synthesis for the biosynthesis of bisanthraquinones by a combination of enzymatic and spontaneous steps are discussed.
- Saha, Nirmal,Mondal, Amit,Witte, Karina,Singh, Shailesh Kumar,Müller, Michael,Husain, Syed Masood
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supporting information
p. 1283 - 1286
(2018/01/27)
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- Phylogenetic Studies, Gene Cluster Analysis, and Enzymatic Reaction Support Anthrahydroquinone Reduction as the Physiological Function of Fungal 17β-Hydroxysteroid Dehydrogenase
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17β-Hydroxysteroid dehydrogenase (17β-HSDcl) from the filamentous fungus Curvularia lunata (teleomorph Cochliobolus lunatus) catalyzes NADP(H)-dependent oxidoreductions of androgens and estrogens. Despite detailed biochemical and structural characterization of 17β-HSDcl, its physiological function remains unknown. On the basis of amino acid sequence alignment, phylogenetic studies, and the recent identification of the physiological substrates of the homologous MdpC from Aspergillus nidulans and AflM from Aspergillus parasiticus, we propose an anthrahydroquinone as the physiological substrate of 17β-HSDcl. This is also supported by our analysis of a secondary metabolite biosynthetic gene cluster in C. lunata m118, containing 17β-HSDcl and ten other genes, including a polyketide synthase probably involved in emodin formation. Chemoenzymatic reduction of emodin by 17β-HSDcl in the presence of sodium dithionite verified this hypothesis. On the basis of these results, the involvement of a 17β-HSDcl in the biosynthesis of other anthrahydroquinone-derived natural products is proposed; hence, 17β-HSDcl should be more appropriately referred to as a polyhydroxyanthracene reductase (PHAR).
- Fürtges, Leon,Conradt, David,Sch?tzle, Michael A.,Singh, Shailesh Kumar,Kra?evec, Nada,Ri?ner, Tea Lani?nik,Müller, Michael,Husain, Syed Masood
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- New Insights into the Conversion of Versicolorin A in the Biosynthesis of Aflatoxin B1
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A crucial and enigmatic step in the complex biosynthesis of aflatoxin B1 is the oxidative rearrangement of versicolorin A to demethylsterigmatocystin. This step is thought to proceed by an oxidation-reduction-oxidation sequence, in which the NADPH-dependent oxidoreductase AflM catalyzes the enclosed reduction step. AflM from Aspergillus parasiticus, after heterologous production in E. coli and purification, however, catalyzed the reduction of the hydroquinoid form of the starting compound versicolorin A (25% conversion) to a so far unknown product of aflatoxin biosynthesis. The asymmetric reduction of emodin hydroquinone to (R)-3,8,9,10-tetrahydroxy-6-methyl-3,4-dihydroanthracen-1(2H)-one (up to 82% for AflM) has also been observed in previous studies using MdpC from Aspergillus nidulans (monodictyphenone biosynthetic gene cluster). The first (nonenzymatic) reduction of emodin to emodin hydroquinone, for example with sodium dithionite, is obligatory for the enzymatic reduction by AflM or MdpC. These results imply an unprecedented role of AflM in the complex enzymatic network of aflatoxin biosynthesis.
- Conradt, David,Sch?tzle, Michael A.,Haas, Julian,Townsend, Craig A.,Müller, Michael
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supporting information
p. 10867 - 10869
(2015/09/15)
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- Synthesis of highly functionalized anthraquinones and evaluation of their antitumor activity
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Highly functionalized anthraquinones which derive from the natural products mensacarcin, islandicin, and chrysophanol have been efficiently synthesized using a Diels-Alder reaction as key step. The introduction of the proposed pharmacophoric side chain unit has been achieved by an addition of an aryllithium species onto different aldehydes. Furthermore, the antitumor activity of these novel compounds has been studied by the in vitro growth inhibition of human lung carcinoma cells of line A549. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Tietze, Lutz F.,Gericke, Kersten M.,Schuberth, Ingrid
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p. 4563 - 4577
(2008/02/12)
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- An efficient total synthesis of chrysophanol and the sennoside C aglycon
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A rapid synthetic approach to the naturally occurring chrysophanol and the sennoside C aglycon is reported. The method involves a three-step protocol starting with commercially available aloin-A to give the two title compounds.
- Kuhnert, Nikolai,Molod, Hoshiar Y.
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p. 7571 - 7573
(2007/10/03)
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- Bulbine-knipholone, a new, axially chiral phenylanthraquinone from Bulbine abyssinica (Asphodelaceae): Isolation, structural elucidation, synthesis, and antiplasmodial activity
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A new natural phenylanthraquinone, bulbine-knipholone (6), has been isolated from the African plant species Bulbine abyssinica (Asphodelaceae). Its structure was determined by spectroscopic and degradative methods. With the aid of the "lactone concept", an atropo-enantioselective total synthesis has been elaborated, confirming the full absolute structure. Bulbine-knipholone exhibits antiplasmodial activity. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Bringmann, Gerhard,Menche, Dirk,Brun, Reto,Msuta, Thomas,Abegaz, Berhanu
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p. 1107 - 1111
(2007/10/03)
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- Atropo-enantioselective total synthesis of knipholone and related antiplasmodial phenylanthraquinones
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The "lactone concept" has been efficiently employed for the first atropo-enantioselective synthesis of knipholone and related natural phenylanthraquinones. Besides the regio- and stereoselective construction of the biaryl axis, another important step was the "synthetically late" introduction of the C-acetyl group, either by a Friedel-Crafts type acetylation or by an ortho-selective Fries rearrangement first tested on simplified model systems and subsequently applied to the highly atroposelective preparation of the natural products and of simplified analogs thereof for biotesting. The synthetic availability of these natural biaryls, their precursors, and their unnatural analogs permitted a broader investigation of the antiplasmodial activities of these interesting biaryls.
- Bringmann, Gerhard,Menche, Dirk,Kraus, Juergen,Muehlbacher, Joerg,Peters, Karl,Peters, Eva-Maria,Brun, Reto,Bezabih, Merhatibeb,Abegaz, Berhanu M.
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p. 5595 - 5610
(2007/10/03)
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- Intramolecular aldol-type condensation between side chains of naphthoquinones: Biomimetic synthesis of 1,6- and 1,8-dihydroxyanthraquinones
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Intramolecular condensation of 2-(acetonyl)-3-acyljuglone derivatives under basic conditions gave 1,6- and/or 1,8-dihydroxyanthraquinones depending on the conditions employed. Treatment of 6-[(3-acetyl-5-methoxy-1,4-dioxo-1,4-dihydro-2-naphthyl)methyl]-2,2- dimethyl-4H-1,3-dioxin-4-one with K2CO3 in alcohol brought about the intramolecular Knoevenagel-type reaction to give 3-hydroxy-8-methoxy-1-methyl-9,10-dioxo-9,10-dihydro-anthracene-2- carboxylates in good yields, while the same naphthoquinone gave 4-hydroxy-5-methoxy-9,10-dioxo-9,10-dihydroanthracene-2-acetic acid in good yield by treatment with potassium bis(trimethylsilyl)amide (KHMDS). Chrysophanol, aloe-emodin, aloesaponarin I, and K1115A were prepared in good yields.
- Uno, Hidemitsu,Masumoto, Akane,Honda, Erina,Nagamachi, Yumi,Yamaoka, Youtarou,Ono, Noboru
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p. 3189 - 3197
(2007/10/03)
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- Inhibitors from rhubarb on lipopolysaccharide-induced nitric oxide production in macrophages: Structural requirements of stilbenes for the activity
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By bioassay-guided separation, three stilbenes (rhapontigenin, piceatannol, and resveratrol), two stilbene glucoside gallates (rhaponticin 2″-O-gallate and rhaponticin 6″-O-gallate), and a naphthalene glucoside (torachrysone 8-O-β-D-glucopyranoside) with inhibitory activity against nitric oxide (NO) production in lipopolysaccharide-activated macrophages were isolated (IC50=11-69μM). The oxygen functions (-OH, -OCH3) of stilbenes at the benzene ring were essential for the activity. The glucoside moiety reduced the activity, while the α,β-double bond had no effect. Furthermore, the active stilbenes (rhapontigenin, piceatannol, and resveratrol) did not inhibit inducible NO synthase activity, but they inhibited nuclear factor-κB activation following expression of iNOS. Copyright
- Kageura, Tadashi,Matsuda, Hisashi,Morikawa, Toshio,Toguchida, Iwao,Harima, Shoichi,Oda, Mamiko,Yoshikawa, Masayuki
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p. 1887 - 1893
(2007/10/03)
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- Antioxidant constituents from rhubarb: Structural requirements of stilbenes for the activity and structures of two new anthraquinone glucosides
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The methanolic extracts from five kinds of rhubarb were found to show scavenging activity for DPPH radical and ·O2-. Two new anthraquinone glucosides were isolated from the rhizome of Rheum undulatum L. together with two anthraquinone glucosides, a naphthalene glucoside, and 10 stilbenes. In the screening test for radical scavenging activity of rhubarb constituents, stilbenes and a naphthalene glucoside showed activity, but anthraquinones and sennosides did not. In addition, most stilbenes inhibited lipid peroxidation of erythrocyte membrane by tert-butyl hydroperoxide. Detailed examination of the scavenging effect on various related compounds suggested the following structural requirements; 1) phenolic hydroxyl groups are essential to show the activity; 2) galloyl moiety enhances the activity; 3) glucoside moiety reduces the activity; 4) dihydrostilbene derivatives maintain the scavenging activity for the DPPH radical, but they show weak activity for ·O2-. In addition, several stilbenes with both the 3-hydroxyl and 4′-methoxyl groups inhibited xanthine oxidase.
- Matsuda, Hisashi,Morikawa, Toshio,Toguchida, Iwao,Park, Ji-Young,Harima, Shoichi,Yoshikawa, Masayuki
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- Method for preparing substituted anthraquinone and application to the preparation of rheins
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PCT No. PCT/FR98/00189 Sec. 371 Date Oct. 2, 1998 Sec. 102(e) Date Oct. 2, 1998 PCT Filed Feb. 2, 1998 PCT Pub. No. WO98/33757 PCT Pub. Date Aug. 6, 1998The invention relates to a process for the preparation of substituted anthraquinones represented by the general formula (I): by Diels-Alder reaction between a 1,4-naphthoquinone of general formula (II): and an acyclic diene of formula (III): CH2=CR-CH=CH-OR3(III) followed by an oxidizing deprotection reaction by means of the Jones reagent, in order to obtain the substituted anthraquinone of general formula (I). Application to the preparation of rheins of use in pharmaceuticals.
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- Process for the preparation of substituted anthraquinones and application in the preparation of rheins
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A process for the preparation of substituted anthraquinones is provided. The anthraquinones can be used to prepare pharmaceutically useful rheins.
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- An expedient and efficient synthesis of naturally occurring hydroxy substituted anthraquinones
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A general method for the synthesis of naturally occurring anthraquinones in high yield via Diels-Alder reaction is reported.
- Khan,Blessing,Schmidt
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p. 255 - 257
(2007/10/02)
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- Method for dyeing keratinous fibres using a monohydroxyindole or dihydroxyindole and a non-oxidizing aromatic carbonyl derivative and dyeing agent
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The present invention relates to a method for dyeing keratinous fibers, characterized in that the following are applied to the fibers: a) a composition (A) containing, in a medium appropriate for dyeing, at least one monohydroxyindole or dihydroxyindole, this application being preceded or followed by the application of b) a composition (B) containing, in a medium appropriate for dyeing, at least one aromatic carbonyl derivative chosen from hydroxyacetophenones, hydroxybenzophenones, 2-hydroxy-1,4-benzoquinones, hydroxy-1,4-naphthoquinones,amino-1,4-naphthoquinones,hydroxy-9,10-anthraquinones and amino-9,10-anthraquinones. It also relates to the dyeing agents for carrying it out.
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- AN ANTHRONE, AN ANTHRAQUINONE AND TWO OXANTHRONES FROM KNIPHOFIA FOLIOSA
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The compounds isoknipholone, isoknipholone anthrone, foliosone and isofoliosone were isolated from the stem of Kniphofia foliosa and their structures determined by spectral analyses.In addition, the known compounds, aloesaponol III, aloesaponol III-8-methyl ether and 4,6-dihydroxy-2-methoxyacetophenone were isolated and identified. - Key words: Kniphofia foliosa; Asphodelaceae; stem; anthrone; anthraquinone; oxanthrones; isoknipholone anthrone; isoknipholone; foliosone; isofoliosone.
- Yenesew, Abiy,Dagne, Ermias,Mueller, Michael,Steglich, Wolfgang
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p. 525 - 528
(2007/10/02)
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- Transition Metal-Catalyzed Oxidations, 6. Total Synthesis of Hallachrome and Related 1,2-Anthraquinones
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9,10-Anthraquinones 3b-3k are prepared by Diels-Alder reaction of juglone (5a) and 7-methyljuglone (5b) with the dienes 4a and 4b, then reduced to the corresponding 1-anthracenols 2b-2d, 2f and 2i that are immediately oxygenated to the ortho-anthraquinones 1b-1d, 1f and 1i with *py*HMPT.The 1,2-anthraquinones dimerize in solution or upon BBr3 treatment.The naturally occurring 1,2-anthraquinone hallachrome (1a) is prepared by selective protection of the bisphenol 3h as monosilyl ether 3i, oxygenation to the silylated ortho-anthraquinone 1i and fluoride-mediated deprotection to 1a. Key words: Hallachrome; 1,2-anthraquinones; 9,10-anthraquinones; oxygenation; 1-anthracenols; Mimoun complex.
- Krohn, Carsten,Khanbabaee, Karamali
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p. 905 - 910
(2007/10/02)
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- ALOECHRYSONE, A DIHYDROANTHRACENONE FROM ALOE BERHANA
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Analysis of the roots of Aloe berhana resulted in the isolation of aloesaponol I, laccaic acid D methyl ester, aloesaponol III, aloesaponarin I, chrysophanol-8-methyl ether, chrysophanol and the new dihydroanthracenone 3,4-dihydro-3,9-dihydroxy-8-methoxy-3-methyl-1(2H)-anthracenone named aloechrysone. Key words: Aloe berhana; Asphodelaceae; roots; leaves; dihydroanthracenones; (R)-aloechrysone; anthraquinones.
- Dagne, Ermias,Casser, Ingrid,Steglich, Wolfgang
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p. 1791 - 1794
(2007/10/02)
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- Biosynthetic Studies on Tajixanthone and Shamixanthone, Polyketide Hemiterpenoid Metabolites of Aspergillus variecolor
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The biosynthesis of tajixanthone and related metabolites of Aspergillus variecolor has been studied by incorporation experiments with simple and advanced precursors labelled with the stable isotopes 13C, 2H and 18O.Tajixanthone is shown to be derived through ring cleavage of an octaketide-derived anthraquinone with introduction of two dimethylallyl moieties.From the results of isotopic labelling experiments and chemical studies on model compounds, an overall biosynthetic pathway is proposed and information on the mechanisms of interconversion of proposed intermediates is obtained.
- Ahmed, Salman A.,Bardshiri, Esfandiar,McIntyre, C. Rupert,Simpson, Thomas J.
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p. 249 - 274
(2007/10/02)
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- Electron Paramagnetic Resonance, ENDOR and TRIPLE Resonance Study of Some 9,10-Anthraquinone Radicals in Solution
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EPR, ENDOR and TRIPLE resonance spectra were recorded for 1,8-dihydroxy-3-methyl-9,10-anthraquinone and 9,10-anthraquinone-2-carboxylic acid anion radicals and the 9,10-anthraquinol-2-carboxylic acid cation radical.EPR spectra were recorded for the 5,8-dideuterio-1,4-dideuterioxy-9,10-anthraquinone anion radical, the 6,7-dideuterio-1,4-dideuterioxy-9,10-anthraquinone anion radical and the 1,4-dihydroxy-9,10-anthraquinol cation radical.The coupling constants of the 1,4-dihydroxy-9,10-anthraquinone anion radical were assigned by deuteriation. KEY WORDS: Substituted 9,10-anthraquinone radicals, EPR, ENDOR
- Vuolle, Mikko,Maekelae, Reijo
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p. 987 - 991
(2007/10/02)
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- A New Synthesis of Anthraquinones Using Dihydro-oxazoles and Grignard Reagents Derived from Mg(Anthracene)(THF)3
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A general synthesis of anthraquinones which depends on the displacement of the methoxy group from an o-methoxyaryldihydro-oxazole by a methoxy substituted benzylmagnesium chloride, generated by using a magnesium-anthracene complex, has been developed.The masked benzylbenzoic acids which result from these reactions are deprotected and then ring-closed to anthrones which on oxidation yield anthraquinones.In this way, the followeing naturally occurring anthraquinones (or derivatives thereof have been synthesized): chrysophanol (9), islandicin (19), digitopurpone (21), tri-O-methylemodin (26), and di-O-methylsoranjidiol (29).
- Nicoletti, Teresa M.,Raston, Colin L.,Sargent, Melvyn V.
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p. 133 - 138
(2007/10/02)
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- A New Synthesis of Anthraquinones
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Methoxy substituted benzyl magnesium chlorides formed by the use of a magnesium anthracene complex smoothly displace the ortho-methoxy group from (o-methoxyaryl)dihydro-oxazoles (oxazolines); the resultant masked o-benzylbenzoic acids are easily converted into anthraquinones.
- Nicoletti, Teresa M.,Raston, Colin L.,Sargent, Melvyn V.
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p. 1491 - 1493
(2007/10/02)
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- A Convenient Synthesis of Isotopically Labelled Anthraquinones, Chrysophanol, Islandicin, and Emodin. Incorporation of Chrysophanol into Tajixanthone in Aspergillus variecolor
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Cycloaddition reactions of labelled 6-methoxy-3-methyl-2-pyrone (1) with naphthoquinones provide the common fungal anthraquinones, chrysophanol (2), islandicin (3), and emodin (4) suitably labelled for biosynthetic studies, as demonstrated by synthesis and incorporation of chrysophanol into the xanthone metabolite, tajixanthone (17) in Aspergillus variecolor.
- Ahmed, Salman A.,Bardshiri, Esfandiar,Simpson, Thomas J.
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p. 883 - 884
(2007/10/02)
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- SYNTHESIS OF SPECIFICALLY O-ALKYLATED ANTHRAQUINONES BY CYCLOADDITION
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Cycloadducts from naphthoquinonoid dienophiles and 1-methoxy-1-trimethylsilyloxy butadienes undergo controlled aromatisation to form chiefly α-hydroxy- or α-methoxy-anthraquinones; this has led to synthesis of several natural O-methyl polyoxyanthraquinones.
- Cameron, Donald W.,Feutrill, Geoffrey I.,Gamble, Glenn B.,Stavrakis, John
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p. 4999 - 5002
(2007/10/02)
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- REACTIONS OF KETENE ACETALS-14; THE USE OF SIMPLE MIXED VINYLKETENE ACETALS IN THE ANNULATION OF QUINONES
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α,β- and β,γ-unsaturated esters can be converted by strong base and chlorotrimethylsilane to the corresponding mixed vinylketene acetals which are shown to be particularly useful and generally applicable reagents for the regiospecific annulation of halogenoquinones.The reaction proceeds readily with a variety of substrates including benzoquinones.
- Savard, Jacques,Brassard, Paul
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p. 3455 - 3464
(2007/10/02)
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- KNIPHOLONE: A UNIQUE ANTHRQUINONE DERIVATIVE FROM KNIPHOFIA FOLIOSA
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The roots of Kniphofia foliosa afforded, in addition to chrysophanol, a novel anthraquinone named knipholone, whose structure was determined by spectroscopic methods as well as by degradation to known compounds.Key Word Index - Kniphofia foliosa; Liliaceae; anthraquinone; chrysophanol; knipholone.
- Dagne, Ermias,Steglich, Wolfgang
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p. 1729 - 1732
(2007/10/02)
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- Novel Oxidative Transformation: Regiospecific Preparation of Naturally Occurring 1-Hydroxyanthraquinones
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A brief reaction sequence for synthesis of the naturally occurring anthraquinones 1-hydroxyanthraquinone (4a), 1-hydroxy-2-methylanthraquinone (4b), pachybasin (4c), chrysophanol (5a), and rhein (5c) has been developed.
- Hauser, Frank M.,Prasanna, Subbarao
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p. 383 - 384
(2007/10/02)
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- SYNTHETISCHE ANTHRACYCLINONE XVI SYNTHESE HYDROXYLIERTER ANTHRACHINONE DURCH REGIOSELEKTIVE DIELS-ALDER-REAKTION
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Naturally occuring quinones such as 7-methyljuglone, chrysophanol, emodin, helminthosporin, phomarin and physcion were prepared via Diels-Alder reaction and PCC-oxidation of the allylic alcohols obtained from the adducts.
- Krohn, Karsten
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p. 3557 - 3560
(2007/10/02)
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