salicylates and 3-5-dibromosalicylic-acid

A method for the determination of Thorium reacting with 3,5-dibromosalicylfluorone, cetyltrimethylammonium bromide and EDTA is proposed. This method is based on the formation of a red-violet colored multicomponent complex in pH 8.8-10.2. The complex has an absorption maximum at 557 nm and its molar absorptivity is 2.19 x 10(5) L.mol-1.cm-1. The Beer Law is obeyed in the concentration range of 0-7 micrograms.25 mL-1 for Th(i.v.). The composition of Th to 3,5-DBSF in the complex is 1:4. All interfering ions may be removed by eluting with 6 mol.L-1 HCl through cation-exchange resin. This method has been used for the determination of Th in Rare-Earth sample ores by ion-exchange separation.

Topics: Bromobenzoates; Chromatography, Ion Exchange; Edetic Acid; Fluoresceins; Salicylates; Sensitivity and Specificity; Spectrophotometry, Ultraviolet; Surface-Active Agents; Thorium

Derivatives of salicylic acid (SA) and benzoic acid prevent endothelin-1 (ET-1) binding to ETA receptors. This study analyzed actions of 30 derivatives of benzoic acid and salicylic acid on (125)I-ET-1 binding to recombinant rat ETA receptors. The most active compounds were 3,5-dibromosalicylic acid (Br2SA, K(i) = 0.5 mM) and 3,5-diiodosalicylic acid (K(i) = 0.3 mM). They were about 50 times more potent than SA and aspirin. Br2SA inhibited equilibrium (125)I-ET-1 binding in an apparently competitive manner. It accelerated 8-fold the dissociation of (125)I-ET-1 receptor complexes and did not modify the second order rate constant of association of (125)I-ET-1 to its receptors. Br2SA also decreased the affinity of ETA receptors for receptor antagonists BQ-123 and bosentan. Br2SA accelerated dissociation of (125)I-ET-1-solubilized ETA receptor complexes and decreased the apparent molecular size of solubilized receptors. Br2SA and 3,5-diiodosalicylic acid inhibited two cellular actions of ET-1: the mobilization of intracellular Ca(2+) stores in isolated cells and contractions of rat aortic rings. They accelerated the relaxing action of BQ-123 and bosentan in ET-1-treated aortic rings. The results suggest the existence of an allosteric modifier site on ETA receptors that recognizes selected derivatives of SA. SA derivatives might be of therapeutic interest to relieve tight ET-1 binding and to favor actions of receptor antagonists.

Topics: Allosteric Regulation; Animals; Aorta; Benzoic Acid; Biological Transport; Bosentan; Bromobenzoates; Calcium; Cells, Cultured; Chromatography, Gel; Drug Interactions; Endothelin Receptor Antagonists; Endothelin-1; Iodine Radioisotopes; Peptides, Cyclic; Rats; Receptor, Endothelin A; Receptors, Endothelin; Recombinant Proteins; Salicylates; Salicylic Acid; Solubility; Sulfonamides; Vasodilation