Showing papers on "Xanthene published in 1978"

Mutagenicity testing of certified food colors and related azo, xanthene and triphenylmethane dyes with the Salmonella/microsome system

Abstract: Thirty-seven azo, xanthene and triphenylmethane dyes including FD and C colors currently approved for use in the U.S.A. and a number of delisted food colors, were tested in the Salmonella/microsome system. In addition to direct plate tests with five tester strains (TA1535, TA100, TA1537, TA1538, TA98), the azo dyes were also assayed after chemical reduction to their component amines. Also, a selected group of azo dyes was subjected to liquid tests (both aerobic with microsomes and anaerobic) and to plate tests involving initial 16 h anaerobic incubations to facilitate microbial reduction of the azo bond. None of the presently listed FD and C colors was mutagenic in any of the test modifications. Among formerly listed colors only Butter Yellow (p-dimethylaminoazobenzene), a recognized animal carcinogen, was mutagenic in the aerobic liquid test. Several other azo dyes were either directly mutagenic, viz. Acid Alizarin Yellow R and Alizarin Yellow GG; required microsomal activation, viz. Acid Alizarin Red B and Methyl Red; or required chemical reduction and microsomal activation, viz. Acid Alizarin Violet N and Sudan IV. Of the non-azo dyes tested only two xanthene dyes appeared to be mutagenic, viz. 9-(2-sulfophenyl)-6-hydroxy-3-isoxanthenone and its 2,4,5,7-tetrabromo derivative.

The Photoreduction of the Silver Ion in a Zinc Oxide Suspension

Abstract: Quantum yields of from 0.235 to 0.385 have been determined for the reduction of Ag+ by the irradiation of 365 nm light on a ZnO surface in aqueous solutions containing 5×10−5 to 1×10−3 M AgClO4. It is proposed that these results can be interpreted by a reaction scheme based on the assumption that some conduction-band electron produced in the ZnO by the irradiation transfers to the Ag+ adsorbed on the ZnO surface. The surface-energy barrier under the present experimental conditions was discussed with the aid of the electrochemical measurement of the ZnO sinter. The photoreduction of Ag+ is optically sensitized by the addition of xanthene dyes, such as Uranine and Rhodamine B. In this case, it is observed that the photoreduction of Ag+ is accompanied by the photolysis of dye molecules. The apparent quantum yields (the number of reacted molecules/the number of photons absorbed in the suspension) of the dye-sensitized photoreduction of Ag+ and the photolysis of dye molecules are 0.015 and 0.007 for Uranine, a...

Photodynamic activity of dyes with different DNA binding properties I. free-radical induction in DNA.

Abstract: The photosensitizing efficiencies of eight dyes have been compared; two acridines, two xanthene derivatives, one sulphur-containing dye and three chemotherapeutic agents. The analysed reaction was the photosensitized induction of free radicals in calf-thymus DNA at low temperature. The binding of these dyes to DNA was first measured. Both strong (process I) and weak (process II) binding, with different intensities, either alone or together, were observed as mode of fixation. Whatever the nature of their binding, all the dyes used revealed a photosensitizing power as inducers of peroxide radicals in DNA. Their relative efficiencies, expressed as a function of the amount of dye molecules bound to DNA, were found to be very different. Intercalation, however, appeared to favour the free-radical induction as the first strongly bound molecules were more efficient.

Synthesis and use of diagnostic radio-pharmaceuticals comprising radioactive isotopes of bromine with dyes

Abstract: A process for preparing bromine-containing dyes labelled with gamma-emitting isotopes of bromine, and the product thereof which is useful as an imaging agent for the hepato-biliary system, particularly in dynamic imaging methods. The dyes prepared are from the class of triarylmethane dyes, and also from the phthalein subclass of the class of xanthene dyes, and the labelling thereof is effected with 76 Br, 77 Br or 82 Br. The process for preparing these dyes involves reacting the non-brominated dye precursor with either 76 Br2, 77 Br2 or 82 Br2. This is a substitution type of reaction in which a ring hydrogen is substituted by either 76 Br, 77 Br or 82 Br.

Electrical insulating composition based on polyolefin containing dye additives as voltage stabilizers

Abstract: A voltage stabilized solid polyolefin dielectric composition is disclosed. The dielectric composition comprises a polyolefin containing a voltage stabilizing amount of an additive selected from the class of dyes identified in the Color Index as being of the solvent type possessing either an azo or a quinoid type structure, or having a xanthene structure exhibiting fluorescence. The solvent dyes must be soluble in or melt miscible with the polyolefin. The solvent dyes must also be stable at the processing temperature and under the conditions of use.

Carboxylation of active methylene compounds using 1,3-diphenylurea, potassium carbonate and carbon dioxide

Abstract: Indene, and fluorene were effectively carboxylated by employing the reagent system, 1,3-diphenylurea, potassium carbonate and carbon dioxide, in organic solvent at room temperature and atmospheric pressure, to produce indenemonocarboxylic acid and fluorene-9-carboxylic acid, respectively. Diphenylurea was almost quantitatively recovered unchanged. Cyclohexanone was slightly carboxylated by the similar procedure. But acetonitrile, acetophenone, dibenzylketone, diphenylmethane, and xanthene were scarcely carboxylated.

Photochemical Reaction of 3,3-Dimethyl-1,2-indanedione with Xanthene

Abstract: The photochemical reaction of 3,3-dimethyl-1,2-indanedione (DMID) with xanthene was investigated in detail. The products are 1-hydroxy-3,3-dimethyl-1-(9-xanthenyl)-2-indanone (3a) (49%), 2-hydroxy-3,3-dimethyl-1-indanone (13%), 1,1′-dihydroxy-3,3,3′,3′-tetramethyl-1,1′-biindan-2,2′-dione (5a) (23%), and 9,9′-bixanthenyl (6) (49%). The reaction proceeds via hydrogen abstraction by 3(nπ)* of DMID leading to triplet radical pair composed of its semidione radical and 9-xanthenyl radical. The product 3a is a combination product from the radical pair, while 5a and 6 are escaping products from it. The hydrogen abstraction occurs at C-1 carbonyl group of DMID in a fairly efficient quantum yield (Φ=0.71). Behavior of the DMID semidione radical is rather resemble those of open-chain semidione radicals than those of sterically hindered semidione radicals.

Polarized absorption spectra and configuration analyses of xanthene and xanthone

Abstract: The polarized absorption sepctra of xanthene and xanthone were measured in stretched poly (vinyl alcohol) films, and the polarization direction of each electronic transition was determined. It was confirmed that xanthone has the short molecular-axis polarized bands (1A1←1A1) at 343, 260, and 226 nm, and the long molecular-axis polarized ones (1BA2←1A1) at 290, 266, and 242 nm. The electronic transitions of xanthone are discussed in connection with those of xanthene by use of the configuration analysis. For the 266 and 260 nm bands, the contributions of the intramolecular charge transfer character from the xanthene skeleton to the carbonyl group are considerable.