Electrochemical transformations of methylxanthines in non-aqueous medium

Coffee, cocoa and tea are the main sources of the natural methylxanthines caffeine, theobromine and theophylline. They are the most consumed alkaloids worldwide, with both beneficial and harmful effects on health. In addition to more traditional therapeutic uses, beneficial effects related to the oxidative stress have been more recently ascribed to these compounds. Moreover, natural methylxanthines have recently attracted attention as bio-based and renewable starting materials for organic synthesis. By using the electron as a green and sustainable reagent, organic electrochemistry provides a precious tool to carry out redox reactions for both mechanistic and synthetic purposes. The electrochemistry of natural methylxanthines was studied previously in an aqueous electrolytes, in which their chemistry is closely related to that of uric acid. Conversely, their electrochemistry in organic solvent is recent history: a few but successful examples of organic electrosyntheses and functionalizations have been reported, with promising applications in the pharmaceutical field. Moreover, some advances in molecular mechanisms might shed light on their potentialities as antioxidants. A prospective is given in the present minireview.