The influence of conversion creatine and guanidinoacetic acid from zwitterionic to cationic form on their solubility in water - a thermodynamic study

Abstract

In this work, the solubility of creatine, creatinine, guanidinoacetic acid and their hydrochlorides in water at atmospheric pressure and in the temperature range T 293.15–313.15 K was determined by the gravimetric method. The thermodynamic parameters of dissolution in water for the mentioned compounds were calculated. The solubility increases significantly by converting the zwitterionic structures of creatine and guanidinoacetic acid into a cationic form, i.e., hydrochloride salt. The effect of increasing solubility is more pronounced for guanidinoacetic acid and decreases with temperature for both compounds. A simple process of transforming the electrically neutral zwitterionic structures into cations represents a good way to increase the solubility in water and bioavailability of biologically active compounds.

Keywords

• solubility
• creatine hydrochloride
• guanidinoacetate hydrochloride
• creatinine