[Equilibrium solubility of new potential drugs in water, 1-octanol and cyclohexane]

A method was developed for the determinations of the exact value of isotherm solubility equilibrium of organic compounds in various solvents, that can be used as a standard operating procedure, too. It was used for the determination of equilibrium solubility data of twenty two new organic compounds in three solvents: water, 1-octanol and cyclohexane. The data of ten imidazo-quinazolone and twelve pyrido-quinazolone derivatives were compared with their chemical structures moreover within and between the structural and solvents series. It was proved, that these compounds are not ideal solutes, due to a specific interaction with the solvents which is constant for the imidazo-quinazolones, while it is randomly altering at the different pyrido-quinazolones. The octanol/water partitioning data were calculated using octanol and water solubility data, and those were compared with separately, accurately measured data obtained by the traditional shake-flask method. Our data support, that--as it can be found in most of the literature--at compounds which form special interaction with the solvent the partition coefficient cannot be calculated from the solubility data, and reversely the water solubility cannot be estimated using the determined partition coefficient and some correction factors. It was demonstrated, that the calculated partition coefficient can be biased randomly up to and order of magnitude, and in some cases even the tendency of those is false in a series.