3-Methylxanthine is a cGMP phosphodiesterase (PDE) inhibitor and a metabolite of theophylline and caffeine .1,2,3 It is formed from theophylline by the cytochrome P450 (CYP) isoform CYP1A2 and from caffeine via 6A5NF-1,3-dimethyluracil, 1,3,7-trimethyluric acid, or theobromine intermediates. 3-Methylxanthine inhibits cGMP PDE in isolated guinea pig trachealis muscle with an IC50 value of 920 ?M.1 It is neurotoxic to mice, inducing convulsions with an ED50 value of 1,107 nmol/kg.4
1.Tanaka, H., Ogawa, K., Takagi, K., et al.Inhibition of cyclic GMP phosphodiesterase by xanthine derivatives relaxes guinea-pig trachealis smooth muscleClin. Exp. Pharmacol. Physiol.18(3)163-168(1991) 2.Camandola, S., Plick, N., and Mattson, M.P.Impact of coffee and cacao purine metabolites on neuroplasticity and neurodegenerative diseaseNeurochem. Res.44(1)214-227(2019) 3.Ha, H.R., Chen, J., Freiburghaus, A.U., et al.Metabolism of theophylline by cDNA-expressed human cytochromes P-450Br. J. Clin. Pharmacol.39(3)321-326(1995) 4.Yamamoto, K., Toyama, E., Kawakami, J., et al.Neurotoxic convulsions induced by theophylline and its metabolites in miceBiol. Pharm. Bull.19(6)869-872(1996)