19F-[1H] nuclear Overhauser effect and proton decoupling of 5-fluorouracil and alpha-fluoro-beta-alanine.
19F-[1H] magnetic double-resonance experiments were performed on model solutions of the antitumor drug 5-fluorouracil (5-FU) and of alpha-fluoro-beta-alanine (FBAL) in order to improve 19F NMR sensitivity for the application in pharmacokinetic studies in vivo. Upon driving the proton spins into saturation, a fluorine signal enhancement (nuclear Overhauser effect) was observed on the order of the theoretical NOE maximum gamma H/2 gamma F = 53% for purely dipolar coupled 19F-1H spin systems in extreme narrowing. The dependence of the effect on proton excitation frequency and temporal parameters was measured and cross-relaxation rate constants of 0.07 s-1 (5-FU) and 0.19 s-1 (FBAL) were determined. Irradiation of the proton spin system by a broad pulse during the 19F signal detection period removed FBAL multiplet splittings completely and narrowed the linewidth of this resonance band by a factor of six. Application of proton presaturation in the 19F NMR examination of a patient undergoing 5-FU chemotherapy enhanced the signal-to-noise ratio of the major 5-FU catabolite FBAL detected noninvasively in the liver.
Krems
B
B
Deutsches Krebsforschungszentrum (DKFZ), Heidelberg, Germany.
Bachert
P
P
Zabel
H J
HJ
Lorenz
W J
WJ
D005472:Fluorouracil / Q000737:chemistry* / Q000493:pharmacokinetics; D006801:Humans; D008099:Liver / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000493:pharmacokinetics
D015091:beta-Alanine; C032348:alpha-fluoro-beta-alanine; D005472:Fluorouracil