Theobromine

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Theobromine
Theobromin - Theobromine.svg
Theobromine3d.png
Systematic (IUPAC) name
3,7-dimethyl-1H-purine-2,6-dione
Clinical data
Legal status
  • Uncontrolled substance
Routes of
administration
Oral
Pharmacokinetic data
Metabolism Hepatic demethylation and oxidation
Biological half-life 7.1±0.7 hours
Excretion Renal (10% unchanged, rest as metabolites)
Identifiers
CAS Number 83-67-0 YesY
ATC code C03BD01 (WHO) R03DA07
PubChem CID: 5429
DrugBank DB01412 YesY
ChemSpider 5236 YesY
UNII OBD445WZ5P YesY
KEGG C07480 YesY
ChEBI CHEBI:28946 YesY
ChEMBL CHEMBL1114 YesY
Synonyms xantheose
diurobromine
3,7-dimethylxanthine
Chemical data
Formula C7H8N4O2
Molecular mass 180.164 g/mol
  (verify)

Theobromine, formerly known as xantheose,[1] is a bitter alkaloid of the cacao plant, with the chemical formula C7H8N4O2.[1] It is found in chocolate, as well as in a number of other foods, including the leaves of the tea plant, and the kola (or cola) nut. It is classified as a xanthine alkaloid,[2] which also include the similar compounds theophylline and caffeine.[1] The compounds differ in their degree of methylation.

Despite its name, the compound contains no brominetheobromine 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 "god food"[3] with the suffix -ine given to alkaloids and other basic nitrogen-containing compounds.[4]

Theobromine is a slightly water-soluble (330 milligrams per litre (0.00019 oz/cu in)[5]), crystalline, bitter powder. Theobromine is white or colourless, but commercial samples can be yellowish.[6] It has a similar, but lesser, effect to caffeine in the human nervous system, making it a lesser homologue. Theobromine is an isomer of theophylline, as well as paraxanthine. Theobromine is categorized as a dimethyl xanthine.[7]

Theobromine was first discovered in 1841[8] in cacao beans by Russian chemist Alexander Voskresensky.[9] Synthesis of theobromine from xanthine was first reported in 1882 by Hermann Emil Fischer.[10][11]

Sources

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

Theobromine is the primary alkaloid found in cocoa and chocolate. Cocoa powder can vary in the amount of theobromine, from 2%[12] theobromine to at least 10%. There are usually higher concentrations in dark than in milk chocolate.[13] Theobromine can also be found in small amounts in the kola nut (1.0–2.5%), the guarana berry, Ilex paraguariensis (yerba mate), and the tea plant.[14] 28 grams (1 oz) of milk chocolate contains approximately 60 milligrams (0.93 grains) of theobromine[15] but 28 g (1 oz) of dark chocolate contains about 200 mg (3.1 gr).[16] Cocoa beans naturally contain approximately 1% theobromine.[17]

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

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

Item Mean theobromine content ratio (103)
Cocoa 20.3
Cocoa cereals 0.695
Chocolate bakery products 1.47
Chocolate toppings 1.95
Cocoa beverages 2.66
Chocolate ice creams 0.621
Chocolate milks 0.226
Carob products 0.000–0.504

Biosynthesis

Theobromine is a purine alkaloid derived from xanthosine, a nucleoside. Cleavage of the ribose and N-methylation yields 7-methylxanthosine. 7-Methylxanthosine in turn is the precursor to theobromine, which in turn is the precursor to caffeine.[20]

Therapeutic uses

In modern medicine, theobromine is used as a vasodilator (a blood vessel widener), a diuretic (urination aid), and heart stimulant.[1]

Theobromine increases urine production. Because of this diuretic effect, and its ability to dilate blood vessels, theobromine has been used to treat high blood pressure.[21] The American Journal of Clinical Nutrition notes that historic use of theobromine as a treatment for other circulatory problems including arteriosclerosis, certain vascular diseases, angina pectoris, and hypertension should be considered in future studies.[22]

Following its discovery in the late 19th century, theobromine was put to use by 1916, when 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.[23]

In the human body, theobromine levels are halved between 6–10 hours after consumption.[21]

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.[24] Possible future uses of theobromine in such fields as cancer prevention have been patented.[25]

Theobromine also shows promise in tooth decay prevention and has been shown in some studies to surpass the more traditional fluoride. Advantages include the ability to safely ingest it, obviating the "do not swallow" warnings on fluoride mouthwash.[26]

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 12% theobromine, 4% theophylline, and 84% paraxanthine.[27]

In the liver, theobromine is metabolized into xanthine and subsequently into methyluric acid.[28] Important enzymes include CYP1A2 and CYP2E1.[29]

Like other methylated xanthine derivatives, theobromine is both a:

  1. competitive nonselective phosphodiesterase inhibitor,[30] which raises intracellular cAMP, activates PKA, inhibits TNF-alpha[31][32] and leukotriene[33] synthesis, and reduces inflammation and innate immunity[33] and
  2. nonselective adenosine receptor antagonist.[34]

As a phosphodiesterase inhibitor, theobromine prevents the phosphodiesterase enzymes from converting the active cAMP to an inactive form.[35] 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 that stimulated the production of cAMP are much longer-lived. In general, the net result is a stimulatory effect.[36]

Effects

Humans

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

The amount of theobromine found in chocolate is small enough that chocolate can, in general, be safely consumed by humans. Theobromine poisoning may result from the chronic or acute consumption of large quantities, especially in the elderly.[37]

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.[38] Therefore, theobromine has a lesser impact on the human central nervous system than caffeine. Theobromine stimulates the heart to a greater degree.[39] While theobromine is not as addictive, it has been cited as possibly causing addiction to chocolate.[40] Theobromine has also been identified as one of the compounds contributing to chocolate's reputed role as an aphrodisiac.[41]

As it is a myocardial stimulant as well as a vasodilator, it increases heartbeat, and also dilates blood vessels, causing a reduced blood pressure.[42] A 2005 paper published suggested that the decrease in blood pressure may be caused by flavanols.[22] Its draining effect allows it to be used to treat cardiac failure, which leads to and is exacerbated by an excessive accumulation of fluid in the body.[42]

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.[43] In the study, 1,000 milligrams (0.035 oz) theobromine (equivalent to ~71 grams (2.5 oz) dark chocolate) significantly increased the threshold of capsaicin concentration required to induce coughs when compared with a placebo.[43] A drug, called BC1036, is being developed by the private UK company infirst Healthcare and it uses theobromine to treat persistent cough.[44] Theobromine is helpful in treating asthma, since it relaxes the smooth muscles, including the ones found in the bronchi.[45]

A study conducted in Utah between 1983 and 1986, and published in 1993, showed a possible association between theobromine and an increased risk of prostate cancer in older men.[46] This association was not found to be linear for aggressive tumors.[46] The association may be spurious, but is plausible.[46] Prenatal and infant exposure to theobromine appeared possibly associated with hypospadias and testicular cancer in one population study.[47]

As with caffeine, theobromine can cause sleeplessness, tremors, restlessness, anxiety, as well as contribute to increased production of urine.[45] Additional side effects include loss of appetite, nausea, vomiting, and withdrawal headaches.

Animals

Animals that metabolize theobromine (found in chocolate) more slowly, such as dogs [1], can succumb to theobromine poisoning from as little as 50 grams (1.8 oz) of milk chocolate for a smaller dog and 400 grams (14 oz), or around nine 44-gram (1.55 oz) small milk chocolate Hershey bars, for an average-sized dog. It should be observed the concentration of theobromine in dark chocolates (approximately 10 g/kg (0.16 oz/lb)) is up to 10 times that of milk chocolate (1 to 5 g/kg (0.016 to 0.080 oz/lb)) - meaning dark chocolate is far more toxic to dogs per unit weight or volume than milk chocolate.

The same risk is reported for cats as well [2], although cats are less likely to ingest sweet food, with most cats 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.[48] Although not usual, the effects of theobromine poisoning, as stated, can become fatal.

In 2014, four American black bears were found dead at a bait site in New Hampshire. A necropsy and toxicology reports performed at the University of New Hampshire in 2015 confirmed they died of heart failure caused by theobromine after they consumed 41 kilograms (90 lb) of chocolate and doughnuts placed at the site as bait. A similar incident killed a black bear cub in Michigan in 2011.[49]

The toxicity for birds is not known, but it is typically assumed that it is toxic to birds.[50]

Gene mutation in mammalian cells

Theobromine is known to induce gene mutations in lower eukaryotes and bacteria. In 1991 and 1997, research by the International Agency for Research on Cancer had shown that genetic mutations occurred in higher eukaryotic cells, specifically cultured mammalian cells. Despite this, theobromine is still listed as safe for human consumption due to inadequate evidence of carcinogenicity.[51]

See also

References

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Further reading

  • Bender, David A.; Arnold E. Bender (1995). A Dictionary of Food and Nutrition. Oxford: Oxford University Press. ISBN 0-19-860961-2.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>