Theobromine

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Theobromine
Systematic (IUPAC) name
3,7-dimethyl-2,3,6,7-tetrahydro-1H-purine-2,6-dione
Identifiers
CAS number	83-67-0
ATC code	C03BD01 R03DA07
PubChem	5429
ChemSpider	5236
Chemical data
Formula	C7H8N4O2[1]
Mol. mass	180.164 g/mol
SMILES	eMolecules & PubChem
Synonyms	xantheose diurobromine 3,7-dimethylxanthine
Pharmacokinetic data
Bioavailability	?
Metabolism	Hepatic demethylation and oxidation[2]
Half life	7.1 +/- 0.7 hours
Excretion	Renal (10% unchanged, rest as metabolites)[2]
Therapeutic considerations
Pregnancy cat.	?
Legal status	Uncontrolled substance
Routes	Oral

Theobromine, also known as xantheose,^[1] is a bitter alkaloid of the cacao plant, found in chocolate, as well as in a number of chocolate-free foods made from theobromine sources including the leaves of the tea plant, the kola or cola nut, and acai berries^{[citation needed]}. It is in the methylxanthine class of chemical compounds,^[3] which also includes the similar compounds theophylline and caffeine.^[1] Despite its name, the compound contains no bromine — 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 brosi ("food"), meaning "food of the gods")^[4] with the suffix -ine given to alkaloids and other basic nitrogen-containing compounds.^[5]

Theobromine is a water insoluble, crystalline, bitter powder; the colour has been listed as either white or colourless.^[6] 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,^[7] which means it is a xanthine^[8] with two methyl groups.^[9]

Theobromine was first discovered in 1841^[10] in cacao beans by Russian chemist Alexander Woskresensky.^[11] Theobromine was first synthesized from xanthine by Hermann Emil Fischer.^[12][13]

[edit] Sources

A chocolate bar and melted chocolate. Chocolate is made from the cacao bean, which is a natural source of theobromine.

Theobromine is the primary alkaloid found in cocoa and chocolate. Cocoa powder such as Hershey's cocoa contains 108 mg of (or 2.16%) theobromine per tablespoon (5g) of powder.^[14] However, cocoa powder with more concentrated amounts of theobromine up to at least 10% also exists.^[15] Chocolate contains 0.5-2.7% theobromine, although white chocolate contains only trace amounts.^[16] Theobromine can also be found in small amounts in the kola nut (1.0-2.5%), the guarana berry, and the tea plant.^[17]

The plant species with the largest amounts of theobromine are:^[18]

• Theobroma cacao
• Theobroma bicolor
• Ilex paraguariensis
• Camellia sinensis
• Cola acuminata
• Theobroma angustifolium
• Guarana
• Coffea arabica

The mean theobromine concentrations in cocoa and carob products are:^[19]

[edit] Therapeutic uses

Following its discovery in the late 19th century, 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.^[20] 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.^[21]

In modern medicine, theobromine is used as a vasodilator (a blood vessel widener), a diuretic (urination aid), and heart stimulant.^[1] In addition, the future use of theobromine in such fields as cancer prevention has been patented.^[22]

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.^[23]

[edit] Pharmacology

Even without dietary intake, theobromine may occur in the body as it is a product of the human metabolism of caffeine which is metabolised in the liver into 10% theobromine, 4% theophylline, and 80% paraxanthine.^[24]

In the liver, theobromine is metabolized into methylxanthine and subsequently into methyluric acid.^[25] Important enzymes include CYP1A2 and CYP2E1.^[26]

As a methylated xanthine, theobromine is a potent Cyclic adenosine monophosphate (cAMP) phosphodiesterase inhibitor;^[8] this means that it helps prevent the enzyme phosphodiesterase from converting the active cAMP to an inactive form.^[27] 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.^[28]

[edit] Effects

[edit] Humans

A diagram of the bronchus. The loosening of the muscles in the bronchus caused by theobromine helps alleviate the symptoms of asthma.

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^[29]. Therefore, theobromine has a lesser impact on the human central nervous system than caffeine. However, theobromine stimulates the heart to a greater degree.^{[citation needed]} While theobromine is not as addictive, it has been cited as possibly causing addiction to chocolate.^[30] Theobromine has also been identified as one of the compounds contributing to chocolate's reputed role as an aphrodisiac.^[31]

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.^[32] However, a recent paper published suggested that the decrease in blood pressure may be caused by flavanols.^[21] Furthermore, its draining effect allows it to be used to treat cardiac failure, which can be caused by an excessive accumulation of fluid.^[32]

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.^[33] In the study, theobromine significantly increased the capsaicin concentration required to induce coughs when compared with a placebo.^[33] Additionally, theobromine is helpful in treating asthma since it relaxes the smooth muscles, including the ones found in the bronchi.^[34]

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.^[35] This association was not found to be linear for aggressive tumors.^[35] While the association may be spurious, it is plausible.^[35]

Theobromine can cause sleeplessness, tremors, restlessness, anxiety, as well as contribute to increased production of urine.^[34] Additional side effects include loss of appetite, nausea, and vomiting.^[36]

[edit] 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. The same risk is reported for cats as well, although cats are less likely to ingest sweet food, having no sweet taste receptors. 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.^[37] Although not usual, the effects of theobromine poisoning, as stated, can become fatal.

[edit] 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.^[38]

[edit] See also

• History of chocolate
• Theobromine poisoning

[edit] References

[edit] Further reading