Complexes of Ergot Alkaloids and Derivatives IV: Investigations into the Nature of Ergot Alkaloid—Xanthine Complexes

Abstract

Studies of the effect of xanthines on the solubility of molecules related to the proteinaceous ergot alkaloids indicate the indole moiety to be a primary site for complexation.The tendency of indole and several analogs to form intermolecular complexes with caffeine was surveyed.This property leads to considerable solubility elevation for many of the compounds examined.Apparent equilibrium or association constants are calculated based on an assumed 1:1 complex between the indole substrate and xanthine ligand.Experimental evidence with several simple indoles and caffeine indicates general adherence to this principle.These relatively uncomplex compounds and even larger more complicated molecules such as methysergide exhibit this property of increased solubility through interaction.These substances may be treated in a somewhat rigorous manner contrary to the intricate proteinaceous alkaloids previously examined.