title: Interaction of doxantrazole with calcium ions in solvents of intermediate polarity. Possible effect of ionization of the drug.
abstract: Spectral evidence is presented that 0.01-0.03 mM solutions of the antiasthmatic drug doxantrazole contain the neutral or ionized form, depending on the solvent and, at least in 1 case, on concentration. In 1,4-dioxane, where only the neutral form exists, and in water, where the drug is ionized, no reaction between doxantrazole and calcium ion can be demonstrated spectroscopically. However, in 2-propanol at 0.01 mM and in 7:3 (v/v) 1,4-dioxane-water the doxantrazole anion can be shown to react with calcium. In more concentrated 2-propanol solutions most of the drug is in the neutral form, and no reaction with calcium is evident. It is suggested that in a biological system doxantrazole can react directly with calcium but such a reaction will depend on the state of the drug and the nature of its environment.
mesh_terms: D002118:Calcium / Q000378:metabolism; D006634:Histamine H1 Antagonists / Q000378:metabolism; D007477:Ions; D012996:Solutions; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet; D013777:Tetrazoles / Q000378:metabolism; D013892:Thioxanthenes / Q000378:metabolism; D044004:Xanthones
chemical_list: D006634:Histamine H1 Antagonists; D007477:Ions; D012996:Solutions; D012997:Solvents; D013777:Tetrazoles; D013892:Thioxanthenes; D044004:Xanthones; D002118:Calcium; C010134:doxantrazole