RESOLUTION OF CATECHOLIC TETRAHYDROISOQUINOLINE ENANTIOMERS AND THE DETERMINATION OF R-SALSOLINOL AND S-SALSOLINOL IN BIOLOGICAL SAMPLES BYGAS-CHROMATOGRAPHY MASS-SPECTROMETRY

Tetrahydroisoquinolines (TIQs) might be formed endogenously and can ac t centrally to promote a mechanism governing alcohol drinking behaviou r. The possibility that biosynthesis occurs through a stereospecific e nzymatic reaction is considered. Several TIQs were transformed into di astereomers by a two-step derivatization with N-methyl-N-trimethylsily ltrifluoracetamid and R-(-)-2-phenylbutyrylic acid and were analyzed b y gas chromatography-mass spectrometry (CC-MS). High resolution of the TIQ enantiomers was achieved. This method was applied to the quantifi cation of the enantiomers of salsolinol (SAL) in urine and plasma of h ealthy humans. Deuterated SAL was used as the internal standard. SAL w as extracted from biological material using phenylboronic phase cartri dges and transformed into diastereomers. The sensitivity and specifici ty of the assay permit the determination of the enantiomeric compositi on of SAL in plasma and urine. The limit of quantification was found t o be 100 pg/ml for each enantiomer. The described method has the advan tage that optimal resolution of the SAL enantiomers without peak overl apping between analyte and other compounds can be achieved. Contrary t o other findings, our GC-MS studies have demonstrated that endogenousl y formed SAL is racemic in plasma as well as in urine of healthy subje cts.