A simple and rapid HPLC method has been developed to analyse all the m
ethylxanthines that can be produced by N-demethylation of 1,3,7-trimet
hylxanthine (caffeine). This method is particularly suitable to study
caffeine metabolism of a filamentous fungus (Aspergillus sp V12A25) cu
ltivated in a synthetic liquid medium containing caffeine as the sole
source of nitrogen.