Influence of pH on aggregation and protein binding of barbituric acid and amylobarbitone

Summary 1 Cryoscopic methods indicated that barbituric acid exists in aqueous solution as a monomer. Amylobarbitone is a monomer at pH 8, but appears to be polymerized at pH 2. The size of the oligomers increases with drug concentration. 2 Using a non-equilibrium dialysis technique supportive evidence for the monomeric form of barbituric acid and the polymerization of amylobarbitone was obtained. The degree of polymerization appeared to increase with fall in pH. Binding constants for these barbiturates with bovine serum albumin were derived, but in acid media no binding was observed.