Theobromine, Caffeine and Theophylline
These three related alkaloids are all found in the beans of coffee plants. They differ in N-methyl substitents- theobromine is methylated at the 3 and 7 positions (purine numbering); caffeine at the 1, 3 and 7 positions and theophylline at the 1 and 3 positions.
Theobromine is also found in the cocoa plant and is the bitter component in chocolate. It causes poisoning in some animals, such as dogs, since they can only metabolise it slowly.
Caffeine is a bitter pyschoactive stimulant, also found in cola and tea. It can cause over-stimulation, sleeplessness and is a diuretic.
Theophylline is also found in tea, cola and cocoa beans and has been used to treat respiratory problems.
There are several species of Coffea which are grown for their beans. The trees produce fruits called "cherries" which are the so-called coffee beans and are not really beans at all!