THE AQUEOUS SOLUBILITY AND THERMAL-BEHAVIOR OF SOME BETA-CARBOLINES

The solubilities of the three beta-carbolines, harmane, harmine and no rharmane, in water at pH 13 have been determined spectrophotometricall y over the temperature range 288-318 K. Plots of logarithms of solubil ity are linear functions of reciprocal temperature, and enthalpies of solution have been determined from these. For comparison, the melting of these compounds has been studied by DSC. All show a single sharp en dothermic transition. However, the enthalpies of fusion are greater th an the enthalpies of solution determined from solubility data, with th e biggest difference ocurring for harmine. In part, this may be a resu lt of the thermal decomposition of this compound contributing to the o bserved transition enthalpy. It is also suggested that acid-base equil ibria significantly affect the solubility.