Theobromine

Overview
Theobromine, also known as xantheose, is a bitter alkaloid of the cacao plant, and is therefore found in chocolate. It is in the methylxanthine class of chemical compounds, which also includes the similar compounds theophylline and caffeine. Despite its name, the compound contains no bromine &mdash; theobromine is derived from Theobroma, the name of the genus of the cacao tree, (which itself is made up of the Greek roots theo ("God") and broma ("food"), meaning "food of the gods") with the suffix -ine given to alkaloids and other basic nitrogen-containing compounds.

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 isolated from the seeds of the cacao tree in 1878 and then shortly afterwards was synthesized from xanthine by Hermann Emil Fischer.

Therapeutic uses
Following its discovery in the late 1800s, theobromine was put to use by 1916, where it was recommended by the publication Principles of Medical Treatment as a treatment for edema (excessive liquid in parts of the body), syphilitic angina attacks, and degenerative angina. The American Journal of Clinical Nutrition notes that theobromine was once used as a treatment for other circulatory problems including arteriosclerosis, certain vascular diseases, angina pectoris, and hypertension.

In modern medicine, theobromine is used as a vasodilator (a blood vessel widener), an aid in urinating, 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.

Pharmacology
In the human liver, theobromine is metabolized into methylxanthine and subsequently into methyluric acid.

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. Cyclic Adenosine Monophosphate 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.

Humans
While theobromine and caffeine are similar in that they are related alkaloids, theobromine has a lesser impact on the human central nervous system and it stimulates the heart to a greater degree. While theobromine is not as addictive, it has been cited as possibly causing addiction to chocolate. A Sexual Odyssey: From Forbidden Fruit to Cybersex discusses how chocolate's alleged aphrodisiac effects may be caused by a number of factors. These include the stimulative effects of theobromine, pleasure induced by the hypothalamus as an effect of chocolate's sweet and fatty nature, or how chocolate affects the levels of serotonin. While serotonin has a pleasurable effect, in high concentrations it can be converted to melatonin which in large amounts reduces sexual drive.

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 2005 study published by Imperial College London concluded that theobromine has an antitussive (cough-reducing) effect superior to codeine by suppressing vagus nerve activity. Additionally, theobromine is helpful in treating asthma since it relaxes the smooth muscles, including the ones found in the bronchi.

There is a possible association between theobromine and an increased risk of suffering from prostate cancer.

Theobromine can cause sleeplessness, tremors, restlessness, anxiety, as well as contribute to increased production of urine. Additional side effects include loss of appetite, nausea, and vomiting.

Animals
The amount of theobromine found in chocolate is small enough that it can be safely consumed by humans, but animals that metabolize theobromine more slowly, such as dogs, can succumb to theobromine poisoning from as little as 50 grams of chocolate for a smaller dog and 400 grams for an average-sized dog. Complications include digestive issues, dehydration, excitability, and a slow heart rate. Later stages of theobromine poisoning include epileptic-like seizures and death. If caught early on, theobromine poisoning is treatable.

Other
Theobromine is known to induce gene mutations in lower eukaryotes and bacteria. At the time of a 1997 report by the IARC, genetic mutations had not been found in higher eukaryotes, such as humans.