Synthesis of Labeled Caffeine - Caffeine: Chemistry, Analysis, Function and Effects - page 85

Definitions of Words and Terms
11 C: Radioactive isotope of carbon (half-life: 20.3 minutes)
13 C: Stable isotope of carbon (natural abundance: 1.10%).
14 C: Radioactive isotope of carbon (half-life: 5700 years).
2 H (deuterium: D), Stable isotope of hydrogen (natural abundance: 0.015%).
Water in which hydrogen is substituted by deuterium is called ''heavy water''.
3 H (tritium: T), Radioactive isotope of hydrogen (half-life: 12.3 years).
15 N: Stable isotope of nitrogen (natural abundance: 0.366%).
High-performance liquid chromatography (HPLC): is an analytical separation
technique connected with a detector (e.g. UV spectroscopy, fluorometry, mass
spectrometry). Preparative scale HPLC is used to purify milligram to gram
quantities.
Thin layer chromatography (TLC): is a technique used to separate a mixture of
compounds on a thin layer of stationary phase coated on a support (glass
plates, aluminium or plastic foils). TLC is convenient to follow up the course
of a chemical reaction. Preparative scale TLC is used to purify up to about 100
milligrams of substance.
Isotope: Two atoms of an element are named ''isotopes'' when their nucleus
contains the same number of protons but a different number of neutrons.
Labeled caffeine: Native caffeine in which one or more atoms have been
substituted by one or more isotopes.
Paraxanthine: 1,7-dimethylxanthine, major metabolite of caffeine in man.
Theobromine: 3,7-dimethylxanthine, the principal alkaloid of cacao bean.
Theophylline: 1,3-dimethylxanthine, alkaloid found in tea.
Xanthine: is the heterocyclic nucleus of the caffeine molecule which can be
viewed as a fusion of a uracil heterocycle (six membered ring) with an
imidazole heterocycle (five membered ring).

d n 0 t 2 n g | 2

Abbreviations
ACN Acetonitrile

DMF Dimethylformamide

DMS Dimethylsulfate

HPLC High-performance liquid chromatography

TLC Thin layer chromatography

References
Arnaud, M. J., Thelin-Doemer, A., Ravussin, E. and Acheson, K. J., 1980.
Study of the demethylation of [1,3,7-Me-13C]-caffeine in man using
respiratory exchange measurements. Biomedical Mass Spectrometry. 7:
521-524.