Raa. Mathot et al., ASSESSMENT OF THE ENANTIOMERIC PURITY OF R AND S-N-6-PHENYLISOPROPYLADENOSINE (PIA) - IMPLICATIONS FOR ADENOSINE RECEPTOR SUBCLASSIFICATION, Naunyn-Schmiedeberg's archives of pharmacology, 350(1), 1994, pp. 109-112
A chiral column high-performance liquid chromatographic method was dev
eloped for the assessment of the enantiomeric purity of the stereoisom
ers of N-6-phenylisopropyladenosine (PIA). The observed chiral purity
of R-PIA was greater than 99.9%, whereas S-PIA was found to contain 4.
4% of the R-enantiomer. In radioligand binding studies, the observed a
ffinity of S-PIA for the adenosine A, receptor (IC50 240 nM) could ent
irely be attributed to its content of R-PIA (IC50 7.8 nM). Calculation
of a theoretical IC50 Of pure S-PIA for the A(2) receptor yielded a v
alue of 6700 nM, which was 35-fold higher than for R-PIA (190 nM). Con
cludingly, the utilization of enantiomeric impure S-PIA in the definit
ion of adenosine receptor subclasses is questionable.