Theobromine is an alkaloid chemical produced by the cacao plant and thus is found in chocolate. Its molecular structure is very closely related to that of caffeine and it has some of the same properties – such as acting as a stimulant – albeit to a lesser extent.

The theobromine molecule.

Although one might expect to find bromine in this chemical, its name is actually derived from the Greek phrase “food of the gods” which is a pretty good description of chocolate!
In addition to being a weak stimulant, theobromine also has some other physiological effects. It can act as a diuretic and has been found to be better than codeine at stopping persistent coughs, due to its effect on the vagus nerve. Theobromine is also responsible for the fact that chocolate is toxic to dogs and some other animals.