HPLC resolution of the enantiomers of dihydroxyphenylalanine and selected salsolinol derivatives using sulfated beta-cyclodextrin.

Abstract

D- and L-dihydroxyphenylalanine (D- and L-DOPA) and enantiomers of the tetrahydroisoquinoline alkaloids salsolinol (SAL), 1-carboxysalsolinol (1-CSAL), and cis-3-carboxysalsolinol (3-CSAL) were chromatographed using sulfated beta-cyclodextrin (S-beta-CD) as a chiral selector in mobile phases with conventional reversed-phase ODS columns. S-beta-CD is a very effective chiral selector for SAL and 3-CSAL, less effective although still useful for resolving D- and L-DOPA, and gives only meager separation of the optical isomers of 1-CSAL. Stoichiometries of the complexes which form between S-beta-CD and SAL enantiomers are 1:1. Interactions between carboxylated substances and S-beta-CD appears to be more complex. Retention of the solutes studied is characterized by favorable negative enthalpy and unfavorable negative entropy changes. Enthalpy changes outweigh entropy values.