Methylxanthines elimination

Similar methods with modifications such as the one by Schutz et al.8 have been in use for over 20 years. In 1968, Ferren and Shane9 published a paper on the differential spectrometric determination of caffeine in soluble coffee and drug combinations. It had the advantage of eliminating a preliminary separation that was required by the earlier method. While the method was successful for coffee, it was not as successful in the determination of caffeine in acetaminophen/phenacetin/caffeine tablets. They proposed that phenacetin was a limiting factor. The official AOAC methods for these methylxanthines in coffee and tea still involve similar methods.10... 

Caffeine pharmacokinetics are nonlinear. For example, when comparing a 500 mg dose to a 250 mg dose, the clearance is reduced and elimination half-life is prolonged with the higher dose (Kaplan et al. 1997). Thus, larger doses prolong the action of the drug. Active metabolites of caffeine are paraxanthine, and to a lesser degree, theobromine, and theophylline. Urinary metabolites are I-methylxanthine, l-methyluric acid, and an acetylated uracil derivative. 

Most recently, genetic engineering opened the opportunity to knock-out caffeine-synthase and eliminate both of the last steps in the biosynthesis, methyla-tion of 7-methylxanthine and theobromine respectively. The goal is to cultivate thereby caffeine-free tea and coffee, without affecting their high polyphenol content as current decaffeination processes do. [511, 512]... 

---