1-Methylxanthine, a caffeine derivative, is an essential human urinary metabolite of caffeine and theophylline (1,3-dimethylxanthine, TP)[1]. 1-Methylxanthine enhances the radiosensitivity of tumor cells[2].
1-Methylxanthine (1-MTX; 3 mM; for 30 min) increases the radiation-induced clonogenic and apoptotic cell (RKO human colorectal cancer cells carrying wild type protein 53 kDa (p53)) death[2].1-Methylxanthine (1MX) exhibits similar activities to other naturally occurring methylxanthines. Unlike caffeine, TP, and theobromine, 3-Methylxanthine (3MX) and 1-methylxanthine do not occur naturally at high levels in plants[1].
[1]. Algharrawi KH, et al. Direct conversion of theophylline to 3-methylxanthine by metabolically engineered E. coli. Microb Cell Fact. 2015 Dec 21;14:203. [2]. Youn H, et al. 1-Methylxanthine enhances the radiosensitivity of tumor cells. Int J Radiat Biol. 2009 Feb;85(2):167-74.