Trapping Acrolein by Theophylline/Caffeine and Their Metabolites from Green Tea and Coffee in Mice and Humans.

Acrolein (ACR) is found exogenously as a widespread environmental pollutant and endogenously, where it is thought to be involved as a pathogenic factor in the progression of many pathological conditions. Eliminating ACR by dietary-active substances has been found to be one potential strategy to prevent ACR-associated chronic diseases. This study first compared the scavenging ACR efficacy of four purine alkaloids, theophylline (TP), paraxanthine (PXT), theobromine (TB), and caffeine (CAF), and then, TP, CAF, and their metabolites were investigated for their ability to trap ACR in vivo. Our results indicated that TP, which possesses an -NH moiety at the N-7 position, exhibits the best ACR-trapping capacity in vitro, while CAF has a slight ability to trap ACR due to the substitutions by -CH3 at the N-1, N-3, and N-7 positions. After oral administration of TP or CAF, the ACR adducts of TP and the metabolites of TP or CAF (e.g., mono- and di-ACR-TP, mono-ACR-1,3-DMU, and mono-ACR-1-MU) were detected in urinary samples obtained from both TP- and CAF-treated mouse groups by using ultra-performance liquid chromatography-tandem mass spectrometry. The quantification studies demonstrated that TP and its metabolites significantly trapped ACR in a dose-dependent manner in vivo. Furthermore, we also detected those ACR adducts of TP and TP/CAF's metabolites in human urine after four cups of green tea (2 g tea leaf/cup) or two cups of coffee (4 g coffee/cup) were consumed per day. Those results indicated that dietary TP or CAF has the potential capacity to scavenge ACR in vivo.