Molecular weight determination of bisbenzyl-isoquinoline alkaloids by 252Cf-plasma desorption mass spectrometer

Bisbenzylisoquinoline alkaloids of Stephania cepharantha have been used for various clinical purposes and recently reevaluated as stimulators of interleukin secretion in tissues. We analyzed molecular stuctures of bisbenzylisoquinoline alkaloids by determining their molecular weights using the 252Cf-plasma desorption mass spectrometry (PDMS). The spectra were accumulated for 500 000 fission events. The acceleration voltage used here was 15 kV. Samples were analyzed using nitrocellulose-coated sample targets. Of the 5 alkaloids studied here, cepharanthine gave a main peak of molecular weight of 606.1 for the theoretical molecular weight of 606.7. The other minor peaks were considered to be demethylated fragment ions. 252Cf-PDMS should be quite useful in studying structure, metabolism and pharmacokinetics of various drugs with extremely low coefficients of variation. (author)