Inosine

A purine nucleoside that has hypoxanthine linked by the N9 nitrogen to the C1 carbon of ribose. It is an intermediate in the degradation of purines and purine nucleosides to uric acid and in pathways of purine salvage. It also occurs in the anticodon of certain transfer RNA molecules. (Dorland, 28th ed)

The primary popular claim made for inosine, that it enhances exercise and athletic performance, is refuted by the available research data. There is some preliminary evidence that inosine may have some neurorestorative, anti-inflammatory, immunomodulatory and cardioprotective effects.