Rb. Vanbreemen et al., FAST-ATOM-BOMBARDMENT TANDEM MASS-SPECTROMETRY OF THE ANTIPARASITIC AGENT PENTAMIDINE AND ITS OXYGENATED METABOLITES, Journal of mass spectrometry., 30(4), 1995, pp. 549-556
Although pentamidine (1,5-bis(4'-amidinophenoxy)pentane) is currently
in use for the treatment of a variety of parasitic infections, includi
ng acquired immune deficiency syndrome-related Pneumocystis carinii pn
eumonia, its metabolism is still under investigation. Positive-ion fas
t atom bombardment mass spectrometry was used with high-energy collisi
on-activated dissociation (CAD) and linked scanning at constant BIE to
obtain tandem mass spectra of protonated molecules of pentamidine and
seven synthetic oxygenated derivatives, which are known metabolites o
f pentamidine. Charge-initiated fragmentation produced abundant fragme
nt ions of m/z 120 and 137 and loss of neutral ammonia from the proton
ated analyte that characterized the amidinophenoxy group. The structur
es of isomeric 2-hydroxypentamidine, 3-hydroxypentamidine and N-hydrox
ypeotamidine could be distinguished based on charge-remote fragmentati
on that produced a series of fragment ions of the pentyl chain and per
mitted the exact location of the hydroxyl group in each molecule to be
determined Next, tandem mass spectra were obtained and the charge-ini
tiated and charge-remote fragmentation discussed for four other metabo
lites of pentamidine, including N,N'-dihydroxypentamidine, 5-(4'-amidi
nophenoxy)pentanoic acid, 5-(4'-amidinophenoxy) pentan-1-ol, and p-hyd
roxybenzamidine. Finally, tandem mass spectrometry was used to identif
y pentamidine and three pentamidine metabolites contained in high-perf
ormance liquid chromatographic (HPLC) fractions from rat Liver perfusa
te and rat urine following treatment with pentamidine. Pentamidine met
abolites identified in rat urine sad liver perfusate using mass spectr
ometry and HPLC retention times included 2-hydroxypentamidine, 3-hydro
xypentamidine and 5-(4'-amidinophenoxy)pentanoic acid.