Theobromine is a water insoluble, crystalline, bitter powder; the colour has been listed as either white or colourless. It has a similar, but lesser, effect to caffeine, making it a lesser homologue. Theobromine is an isomer of theophylline as well as paraxanthine. Theobromine is categorized as a dimethyl xanthine, which means it is a xanthine with two methyl groups.
Theobromine was first discovered in 1841 in cacao beans by Russian chemist Alexander Woskresensky. Theobromine was first isolated from the seeds of the cacao tree in 1878 and then shortly afterwards was synthesized from xanthine by Hermann Emil Fischer.
Theobromine is the primary alkaloid found in cocoa and chocolate. Cocoa powder such as Hershey's cocoa contains 108mg of (or 2.16%) theobromine per tablespoon (5g) of powder. However, cocoa powder with more concentrated amounts of theobromine up to at least 10% also exists. Chocolate contains 0.5-2.7% theobromine, although white chocolate contains only trace amounts. Theobromine can also be found in small amounts in the kola nut (1.0-2.5%), the guarana berry, and the tea plant.
The mean theobromine concentrations in cocoa and carob products are:
|Item||Mean theobromine content (mg/g)|
|Chocolate bakery products||1.47|
|Chocolate ice creams||0.621|
In modern medicine, theobromine is used as a vasodilator (a blood vessel widener), a diuretic (urination aid), and heart stimulant. In addition, the future use of theobromine in such fields as cancer prevention has been patented.
Theobromine has also been used in birth defect experiments involving mice and rabbits. A decreased fetal weight was noted in rabbits following forced feeding, but not after other administration of theobromine. Birth defects were not seen in rats.
As a methylated xanthine, theobromine is a potent Cyclic adenosine monophosphate (cAMP) phosphodiesterase inhibitor; this means that it helps prevent the enzyme phosphodiesterase from converting the active cAMP to an inactive form. cAMP works as a second messenger in many hormone- and neurotransmitter-controlled metabolic systems, such as the breakdown of glycogen. When the inactivation of cAMP is inhibited by a compound such as theobromine, the effects of the neurotransmitter or hormone which stimulated the production of cAMP are much longer lived. The net result is generally a stimulatory effect.
While theobromine and caffeine are similar in that they are related alkaloids, theobromine is weaker in both its inhibition of cyclic nucleotide phosphodiesterases and its antagonism of adenosine receptors. Therefore, theobromine has a lesser impact on the human central nervous system than caffeine. However, theobromine stimulates the heart to a greater degree. While theobromine is not as addictive, it has been cited as possibly causing addiction to chocolate. Theobromine has also been identified as one of the compounds contributing to chocolate's reputed role as an aphrodisiac.
As it is a myocardial stimulant as well as a vasodilator, it increases heartbeat, yet it also dilates blood vessels, causing a reduced blood pressure. However, a recent paper published suggested that the decrease in blood pressure may be caused by flavanols. Furthermore, its draining effect allows it to be used to treat cardiac failure, which can be caused by an excessive accumulation of fluid.
A 2004 study published by Imperial College London concluded that theobromine has an antitussive (cough-reducing) effect superior to codeine by suppressing vagus nerve activity. In the study, theobromine significantly increased the capsaicin concentration required to induce coughs when compared with a placebo. Additionally, theobromine is helpful in treating asthma since it relaxes the smooth muscles, including the ones found in the bronchi.
A study conducted in Utah between 1983 and 1986, and published in 1993, showed a possible association between theobromine and an increased risk of suffering from prostate cancer in older men. This association was not found to be linear for aggressive tumors. While the association may be spurious, it is plausible.