|Metabolism||Hepatic demethylation and oxidation|
|Elimination half-life||7.1±0.7 hours|
|Excretion||Renal (10% unchanged, rest as metabolites)|
|Chemical and physical data|
|Molar mass||180.164 g/mol g·mol−1|
|3D model (JSmol)|
Theobromine, formerly known as xantheose, is a bitter alkaloid of the cacao plant, with the chemical formula C7H8N4O2. It is found in chocolate, as well as in a number of other foods, including the leaves of the tea plant, and the kola nut. It is classified as a xanthine alkaloid, others of which include theophylline and caffeine. The compounds differ in that caffeine has an extra methyl group (see under Pharmacology section).
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 broma ("food"), meaning "food of the gods") with the suffix -ine given to alkaloids and other basic nitrogen-containing compounds.
Theobromine is a slightly water-soluble (330 mg/L), crystalline, bitter powder. Theobromine is white or colourless, but commercial samples can be yellowish. It has an effect similar to, but lesser than, that of 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.
Theobromine was first discovered in 1841 in cacao beans by Russian chemist Aleksandr Voskresensky. Synthesis of theobromine from xanthine was first reported in 1882 by Hermann Emil Fischer.
Theobromine is the primary alkaloid found in cocoa and chocolate. Cocoa powder can vary in the amount of theobromine, from 2% theobromine, up to higher levels around 10%. Cocoa butter only contains trace amounts of theobromine. There are usually higher concentrations in dark than in milk chocolate. Theobromine can also be found in small amounts in the kola nut (1.0–2.5%), the guarana berry, yerba mate (Ilex paraguariensis), and the tea plant. 28 grams (1 oz) of milk chocolate contains approximately 60 milligrams (1 grain) of theobromine, while the same amount of dark chocolate contains about 200 milligrams (3 grains). Cocoa beans naturally contain approximately 1% theobromine.
- Theobroma cacao – seed and seed coat
- Theobroma bicolor – seed coat
- Ilex paraguariensis – leaf
- Camellia sinensis – leaf
|Item||Mean theobromine content ratio (10−3)|
|Chocolate bakery products||1.47|
|Chocolate ice creams||0.621|
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.
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.
Like other methylated xanthine derivatives, theobromine is both a:
- competitive nonselective phosphodiesterase inhibitor, which raises intracellular cAMP, activates PKA, inhibits TNF-alpha and leukotriene synthesis, and reduces inflammation and innate immunity and
- nonselective adenosine receptor antagonist.
As a phosphodiesterase inhibitor, theobromine prevents the phosphodiesterase enzymes 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 that stimulated the production of cAMP are much longer-lived. In general, the net result is a stimulatory effect.
The amount of theobromine found in chocolate is small enough that chocolate can, in general, be safely consumed by humans. At doses of 0.8–1.5 g/day (50–100 g cocoa), sweating, trembling and severe headaches were noted, with limited mood effects found at 250 mg/day.
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. The potential inhibitory effect of theobromine on phosphodiesterases is seen only at amounts much higher than what people normally would consume in a typical diet including chocolate.
Animals that metabolize theobromine (found in chocolate) more slowly, such as dogs, 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 bars, for an average-sized dog. 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, 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. Although not common, the effects of theobromine poisoning can be fatal.
In 2014, four American black bears were found dead at a bait site in New Hampshire. A necropsy and toxicology report 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.
The toxicity for birds is not known, but it is typically assumed that it is toxic to birds.
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Mean theobromine and caffeine levels respectively, were 0.695 mg/g and 0.071 mg/g in cocoa cereals; 1.47 mg/g and 0.152 mg/g in chocolate bakery products; 1.95 mg/g and 0.138 mg/g in chocolate toppings; 2.66 mg/g and 0.208 mg/g in cocoa beverages; 0.621 mg/g and 0.032 mg/g in chocolate ice creams; 0.226 mg/g and 0.011 mg/g in chocolate milks; 74.8 mg/serving and 6.5 mg/serving in chocolate puddings.... Theobromine and caffeine levels in carob products ranged from 0–0.504 mg/g and 0-0.067 mg/g, respectively.
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