Gas chromatographic determination of pargyline and pargyline amine metabolites after derivatization with isobutyl chloroformate

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Abstract
Pargyline (I) and four of its major amine metabolites, N-benzylpropargylamine (II), N-methylpropargylamine (IV), N-benzylmethylamine (VI) and pargyline N-oxide (VIII), were determined by g.l.c. after reaction with isobutyl chloroformate in a two-phase system. Pargyline and metabolite IV which form the same derivative, were separated quantitatively by liquid-liquid distribution before derivatization with isobutyl chloroformate. Also, metabolites VI and VIII form identical derivatives, and as they could not be easily separated, VIII was reduced to I before derivatization. The analytical method was applied in studies of the metabolism of pargyline in microsomes from phenobarbitone pretreated rats. The metabolism was rapid, leading mainly to the formation of II, IV, VI and VIII. 92% of the substrate was consumed during the first min of incubation at an initial substrate concentration of 100 μM (32 nmol mg−1 protein), and II, IV, VI and VIII accounted for 83% of formed metabolites. The metabolite II was further metabolized while the levels of IV, VI and VIII remained constant after 5 min. It was possible to determine 0.5 μM of pargyline, II and VI in microsomal incubations, with an r.s.d. of <5% (n = 6). N-Methylpropargylamine (IV) was positively identified and quantitated as a pargyline metabolite for the first time.