Degradation Characteristics of Two Tetrahydroisoquinolines at Room and Body Temperatures: HPLC Determination with Electrochemical Detection

Abstract

Reversed-phase high-pressure liquid chromatography (HPLC) was utilized to determine the stability of tetrahydropapaveroline (THP) and salsolinol at two ambient temperatures and over varying time intervals of up to 27 hr. Although ascorbate, an antioxidant, was shown to retard the temporally contingent degradation of THP at both 22°C and 37°C, the breakdown of the tetrahydrosoquinoline product was more pronounced at 37°C. Salsolinol was virtually stable under all conditions. The formation of detectable by-products of THP was demonstrated by the presence of secondary peaks in the THP-water assay which were strikingly absent in the THP-ascorbate aliquots. Finally, the HPLC profiles of five THP samples obtained from four different sources revealed the presence of similar secondary peaks which varied considerably in shape and peak height from one sample to another. The implications of this lack of uniformity of THP for pharmacological studies of addictive processes is discussed.