Tetramethyluric acid(Theacrine) is a small alkaloid molecule that is essentially a structurally modified version of caffeine. The chemical is actually made from caffeine found in certain plants. These plants then accumulate theophylline, which gives us a natural source.
It has shown early promise in recent studies. It appears to have similar effects to caffeine, but is less tolerated. This means you can continue to take small doses of Tetramethyluric acid to achieve the same effect over time.