Xanthen-l-ones

All the phenalenones so far isolated from plants are derivatives of 9-phenyl-lH-phenalen-1-one (44). All the related compounds occurring with them may be regarded as metabolic oxidation products phenyl-naphthalides, phenylnaphthalic anhydrides, quinonemethides derived from oxa- and aza-phenalenones, derivatives of lH-naphtho[2,l,8- wia]-xanthen-l-one (45) and a phenalenone dimer. 

The structure 8,9,1 l-trihydroxy-lH-naphtho[2,l,8-wna]xanthen-l-one was proposed for the isomeric pigment haemofluorone B 62) on the basis of the nmr data obtained for the trimethyl ether as shown on structure (61). However further consideration of model compounds (77) suggests that the spectrum is more consistent with structure (62). This also seems more in accord with biosynthetic concepts. 

The structure 2,5-dihydroxy-lH-naphtho[2,l,8-wna]xanthen-l-one proposed for the natural pigment lachnanthofluorone (53) does not seem to be consistent with the published nmr data, and a synthetic sample of... 

It has been demonstrated that photolysis of 6-hydroxy-9-phenyl-phenalenones is an efficient method for synthesis of IH-naphtho-[2,l,8-w a]xanthen-l-one and its derivatives (62, 69). They have also been prepared by acid catalyzed cyclization of 6-hydroxy-9-(2-methoxy-phenyl) phenalenones 70, 71). For example cyclization and decarboxylation convert 7-carboxy-2,5-dimethoxy-6-hydroxy-9-(2-methoxy-... 

Cooke, R. G., and I. J. DaGley Synthesis and Spectroscopic Properties of IH-Naphtho[2,l,8-m a]xanthen-l-one and its 8-Methoxy Derivative. Tetrahedron Letters 637 (1978). 

L,9,9a.-Tetrahydro-3-hydroxy-42L,7,9si-trimethoxy-2- l-oxo-3-phenyl-2-propeny[)-lH-xanthen-l-one, 9CI [157878-12-1]... 

Bengal Rose 3,4,5,7-Tetrachloro-3, 6 -dihydroxy-spiro[isobenzofuran-l(3H), 9 -[9H]xanthen]-3-one] disodium salt... 

Interestingly, the use of Sc(OTf)3 as the promoter gave hydroxyalkyl-6,7-dihydrobenzofuran-4(57/)-one derivatives 17 from D-ribose (9), whereas scandium cation-exchanged montmorillonite (Sc -mont) afforded hydroxyalkyl-3,3,6,6,-tetramethyl-3,4,5,6,7,9-hexahydro-l//-xanthene-l,8(27/)-dione (18) in good yield [97] (Scheme 3). 

The ORAC method was first proposed by Cao and co-workers in 1993. Like in the TRAP method, they used a fluorescent indicator. Determination of antioxidant activity by this method is based on measurement of decreasing fluorescence of the indicator caused by the radicals generated in the system. The reaction mixture in their proposal consisted of a fluorescent indicator p-phycoerythrin (p-PE), 2,2 -azobis(2-amidinopropane) dihydrochloride (AAPH) as a peroxyl radical generator and the analysed sample [42]. Attributing the low purity of p-phycoerythrin (approx. 30%) to the low reproducibility of fluorescence and the occurrence of different forms of phycoerythrin, Ou and co-workers [43] modified the method by replacing the indicator with fluorescein (3, 6 -dihydroxyspiro[isobenzofuran-l[3H],9 [9H]-xanthen]-3-one). 

A similar method, which involves the formation of the epoxide through reaction of diazomethane on l-formyl-2-hydroxyxanthone, leads directly to ll -furo[2,3-a]xanthen-ll-one.321... 

Fluorescein (FL) (3, 6 -dihydroxyspiro[isobenzofuran-l[3H], 9 [9H]-xanthen]-3-one) was used for the ORAC assay. Excitation and emission filters of 490 and 520 nm, respectively, were used. A stock solution of 1.2 mM FL was diluted to a working solution of 94 nM made up in 0.75 mM phosphate buffer (pH 7.4). Two pipettors, which were part of the microplate... 

SODIUM SODIUM FLUORESCEIN SODIUM FLUORESCEINATE SODIUM SALT of HYDROXY-o-CARBOXY-PHENYL-FLUORONE SOLUBLE FLUORESCEIN SPIRO(ISOBENZOFURr N)-l(3H),9 -(9H)XANTHENE-3-ONE, 3, 6 -DIHYDROXY-DISODIUM SALT URANTN URANINE A EXTRA URANINE USP XII URANINE YELLOW 11824 YELLOW ... 

SPIRO(ISOBENZOFURAN)-l(3H),9 -(9H)XANTHENE-3-ONE, 3, 6 -DIHYDROXY-DISODIUM SALT see FEWOOO... 

A series of novel l, 3-dihydroxyxanthone Mannich base derivatives were synthesized, structure elucidated, and evaluated for anticholinesterase activity. Most of the target compounds exhibited moderate to good inhibitory activities with the IC50 values at micromole level concentration against both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Among them, 2 - ((diethylamino )methyl) -1 -hydroxy- 3 - (3 -methylbut-2-enyloxy) -9H-xanthen-9-one showed potent inhibitory activity against AChE and the best inhibitory activity against BuChE. The Mannich base derivatives were likely to bind to the active site (AS) and the peripheral anionic site (PAS) of cholinesterases [169]. 

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