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Showing papers on "Xanthone published in 1991"


Journal ArticleDOI
TL;DR: The structure of new xanthone from Swertia chirayita has been established as 1,5-dihydroxy-3,8-dimethoxy Xanthone (chiratol) on the basis of spectral and chemical evidence.

46 citations


Journal ArticleDOI
TL;DR: Vinaxanthone is a novel phospholipase C inhibitor produced by Penicillium vinaceum Gilman and about NR6815 as mentioned in this paper, which has been elucidated as a polycyclic xanthone with poly acidic functional groups based on various NMR studies.

44 citations


Journal ArticleDOI
TL;DR: In this paper, from a dichloromethane extract of the aerial parts and from a methanolic root extract of Chironia krebsii, 11 1-hydroxyxanthones and six xanthone glycosides have been isolated.

39 citations



Journal ArticleDOI
TL;DR: A new xanthone, 2-(3-hydroxy-3-methylbutyl)-1,3,5,6-tetrahydroxyxanthone was isolated from the heart-wood of Calophyllum inophyllus.

32 citations


Journal ArticleDOI
TL;DR: The photochemistry of xanthone complexed with cyclodextrins (α-, β- and γ-CD) in the solid state has been examined by diffuse reflectance laser flash photolysis as mentioned in this paper.
Abstract: The photochemistry of xanthone complexed with cyclodextrins (α-, β- and γ-CD) in the solid state has been examined by diffuse reflectance laser flash photolysis. The first half-life for xanthone triplet decreases as the size of the CD cavity increases; long-lived ketyl radicals are observed in the cases of β- and γ-CD. These changes in photobehavior are attributed to the restrictions on the mobility of included xanthone imposed by the CD structure.

23 citations


Journal ArticleDOI
TL;DR: The first bisxanthone C-glycoside,swertipunicoside,was isolated from the whole plant of swertia punicea Hemsl.
Abstract: The first bisxanthone C-glycoside,swertipunicoside,was isolated from the whole plant of swertia punicea Hemsl. and its strucutre elucidated through spectroscopic,particulary selective INEPT NMR,analysis as 1,5,8-trihydroxy-3-methoxy-7-(1',3',6',7'-tetrahydroxy-9'-oxo-4'-xanthyl)xanthone 2'-C-β-D-glucopyranoside

20 citations


Journal ArticleDOI
TL;DR: In this article, the rotational envelope has been analyzed and it is concluded that the intensity of the T 1 origin band mainly comes from the direct spin-orbit coupling with the S 2 1 A 1 (ππ*) state.

16 citations


Journal ArticleDOI
TL;DR: In this article, 13C-NMR spectroscopic analysis of the enriched products demonstrated a labelling pattern indicating that the antibiotic is derived from a polyketide which undergoes rearrangement by a mechanism unique for xanthone biosynthesis.
Abstract: The biosynthesis of citreamicin 1 has been studied by feeding 13C- and 18O-labelled precursors to Micromonospora citrea cultures. 13C-NMR spectroscopic analysis of the enriched products demonstrated a labelling pattern indicating that the antibiotic is derived from a polyketide which undergoes rearrangement by a mechanism unique for xanthone biosynthesis.

12 citations



Journal ArticleDOI
TL;DR: In this paper, the photoreduction of xanthone with diethylaniline in cyclodextrin cavities was studied at 77 k and room temperature by a time-resolved ESR technique.
Abstract: The photoreduction of xanthone with diethylaniline in cyclodextrin cavities was studied at 77 K and room temperature by a time-resolved ESR technique. The radical pair observed in β- and γ-cyclodex...

Journal ArticleDOI
TL;DR: Three new xanthone 2,4-di- C -glycosides and two of its O -rhamnosides have been found in aerial parts of the fern Asplenium adiantum-nigrum.

Journal ArticleDOI
TL;DR: The 1,3,6,8-tetraoxygenated xanthone structure assigned to a compound from Halenia elliptica is incorrect as discussed by the authors, based on published evidence, the Xanthone appears to be 1-hydroxy-2, 3, 7-trimethoxyxanthone.

Journal ArticleDOI
TL;DR: The benzene whole plant extract of Hoppea fastigiata yielded a new xanthone, 1,5,7-trihydroxy-3methoxyxanthone as discussed by the authors.


Journal ArticleDOI
01 Jan 1991
TL;DR: The isolation and structure elucidation of a new xanthone, 1,7-dihydroxy-3,5-dimethoxyxanthone from the aerial parts and roots of Hoppea fastigiata is reported.
Abstract: The petroleum ether (60-80°) extract of the whole plants (aerial parts and roots) of Hoppea fastigiata yielded a new xanthone, 1,7-dihydroxy-3,5-dimethoxyxanthone.Hoppeu fustigiutu Clarke (Gentianaceae) (1) was collected from Santiniketan and identified. The plants are used by tribes for a variety of ailments and apparently have not been investigated previously. In continuation of our studies on plant pigments (2-6), we now report the isolation and structure elucidation of a new xanthone, 1,7-dihydroxy-3,5-dimethoxyxanthone from the aerial parts and roots of this species. This substitution pattern is extremely uncommon in xanthones and is reported previously by Rama Rao et al. (7).

Journal ArticleDOI
TL;DR: It is shown that DHXD is a cytosolic enzyme, induced by growth on xanthone and maximally expressed during the stationary phase of growth, and the activity of this extradiol meta-fission dioxygenase is characterized in terms of its basic enzymological properties.
Abstract: Bacterial extradiol ring-fission dioxygenases play a critical role in the transformation of multiring aromatic compounds to more readily biodegradable aromatic or aliphatic intermediates. Arthrobacter sp. strain GFB100 utilizes an extradiol meta-fission dioxygenase, 3,4-dihydroxyxanthone dioxygenase (DHXD), in the catabolism of the three-ring oxygen heterocyclic compound xanthone. In this paper, we show that DHXD is a cytosolic enzyme, induced by growth on xanthone and maximally expressed during the stationary phase of growth. In addition, we characterize the DHXD activity in terms of its basic enzymological properties. 1,10-Phenanthroline and H2O2 treatments eliminated DHXD activity, indicating that the enzyme required Fe2+ ions for activity. Other divalent cations were either inhibitory or had no effect on activity. DHXD had a temperature optimum of 30 degrees C and a pH optimum of 7.0. DHXD followed typical saturation kinetics and had an apparent Km of 10 microM for 3,4-dihydroxyxanthone. The dye celestine blue served as a noncompetitive DHXD inhibitor (Ki, 5 microM). Several other structural analogs served neither as substrates nor inhibitors. DHXD was thermally labile at temperatures above 40 degrees C. The half-life for thermal DHXD inactivation was 5 min at 40 degrees C. DHXD activity was completely stable through one freeze-thaw cycle, and about 80% of the DHXD activity remained after 2 days of incubation at 0 degree C. The apparent tight binding of the Fe2+ cofactor to DHXD may be a factor contributing to the stability of this extradiol dioxygenase when it is stored.

Journal ArticleDOI
TL;DR: Xanthone 1,4-dihydropyridine derivatives are weak calcium antagonists but exert potent selective bradycardic effects.
Abstract: A series of xanthone 1,4-dihydropyridine derivatives were prepared. The compounds were evaluated for inotropic, chronotropic and calcium antagonistic properties. The tested compounds are weak calcium antagonists but exert potent selective bradycardic effects.

Journal ArticleDOI
TL;DR: A new synthetic route to norlichexanthone (1,3,6-trihydroxy-8-methyl- 9H-xanthen-9one) derivatives has been developed by using a Smiles rearrangement of an appropriately substituted depside in the key step as mentioned in this paper.
Abstract: A new synthetic route to norlichexanthone (1,3,6-trihydroxy-8-methyl- 9H-xanthen-9-one) derivatives has been developed by using a Smiles rearrangement of an appropriately substituted depside in the key step. 2,4,7-Trichloronorlichexanthone (22) and 4,5,7- trichloronorlichexanthone (29) have been prepared by this method. The former xanthone (22) was shown to be a constituent of the lichens Lecanora sulphurata and L. flavo-pallescens and the latter (29) a constituent of Micarea austroternaria var. isabellina.

Journal ArticleDOI
TL;DR: The structure of a new pentaoxygenated xanthone isolated from the fern Cystopteris fragilis has been determined as 1,3-dihydroxy-5,6,7-trimethoxyxanthone by spectroscopic methods and chemical reactions.
Abstract: A new pentaoxygenated xanthone has been isolated from the fern Cystopteris fragilis. Its structure has been determined as 1,3-dihydroxy-5,6,7-trimethoxyxanthone {1} by spectroscopic methods and chemical reactions



Journal ArticleDOI
TL;DR: In this paper, 13C-NMR spectroscopic analysis of the enriched products demonstrated a labelling pattern indicating that the antibiotic is derived from a polyketide which undergoes rearrangement by a mechanism unique for xanthone biosynthesis.
Abstract: The biosynthesis of citreamicin 1 has been studied by feeding 13C- and 18O-labelled precursors to Micromonospora citrea cultures. 13C-NMR spectroscopic analysis of the enriched products demonstrated a labelling pattern indicating that the antibiotic is derived from a polyketide which undergoes rearrangement by a mechanism unique for xanthone biosynthesis.