Theobromine, also known as xantheose, is the principal alkaloid of Theobroma cacao (cacao plant).[ It is found in chocolate, as well as in a number of other foods, including tea ( Camellia sinensis), some American Holly (Ilex vomitoria and Ilex guayusa) and the kola nut. It is a white or colourless solid, but commercial samples can appear yellowish.][
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Theobromine, a metabolite of caffeine, is processed in the liver into xanthine and methyluric acid, peaks in the blood 2–3 hours after ingestion due to its fat solubility, and primarily acts by inhibiting adenosine receptors with minor phosphodiesterase inhibition. It is a mild heart stimulant and bronchodilator in humans with limited central nervous system effects. It can be toxic or fatal to animals like dogs and cats due to their slower metabolism of the compound.
Structure
Theobromine is a flat molecule,[
]
History
Theobromine was first discovered in 1841
Etymology
Theobromine is derived from Theobroma, the name of the genus of the cacao tree, with the suffix -ine given to alkaloids and other basic nitrogen-containing compounds.[ (note: the book incorrectly states that the name "theobroma" is derived from Latin)]
Despite its name, the compound contains no bromine, which is based on Greek bromos ("stench").
Sources
Theobromine is the primary alkaloid found in Cocoa bean and chocolate. Cocoa butter only contains trace amounts of theobromine. There are usually higher concentrations in dark than in milk chocolate.
There are approximately of theobromine in of milk chocolate,
Plant species and components with substantial amounts of theobromine are:
Theobromine can also be found in trace amounts in the kola nut, the guarana berry, yerba mate ( Ilex paraguariensis),
The mean theobromine concentrations in cocoa and carob products are:
| +
! Item
! Mean theobromine per 100 g |
| Cocoa powder | 2060 mg |
| Cocoa beverages | 266 mg |
| Chocolate toppings | 195 mg |
| Chocolate bakery products | 147 mg |
| Cocoa cereals | 69.5 mg |
| Chocolate ice creams | 62.1 mg |
| 22.6 mg |
| Carob products | 0.00–50.4 mg |
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.
Pharmacology
[[File:Caffeine metabolites.svg|class=skin-invert-image|thumb|250px|Caffeine is metabolized in the liver into three primary metabolites:
paraxanthine (84%), theobromine (12%), and theophylline (4%)|alt=A diagram featuring 4 skeletal chemical formulas. Top (caffeine) relates to similar compounds paraxanthine, theobromine and theophylline.]]
Even without dietary intake, theobromine may occur in the body as it is a product of the human metabolism of caffeine, which is metabolism in the liver into 12% theobromine, 4% theophylline, and 84% paraxanthine.
In the liver, theobromine is metabolized into xanthine and subsequently into methyluric acid.
Unlike caffeine, which is highly water-soluble, theobromine is only slightly water-soluble and is more fat soluble, and thus peaks more slowly in the blood. While caffeine peaks after only 30 minutes, theobromine requires 2–3 hours to peak.
The primary mechanism of action for theobromine inside the body is inhibition of adenosine receptors.[ Its effect as a phosphodiesterase inhibitor][
]
Effects
Humans
Theobromine is a heart stimulator and diuretic but has no significant stimulant effect on the human central nervous system.[ It is a bronchodilator and causes relaxation of vascular smooth muscle.][ It is available as a prescription drug in South Korea.]
Compared with caffeine, theobromine is weaker in both its inhibition of cyclic nucleotide phosphodiesterases and its antagonism of adenosine receptors.
Toxicity
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.
Also, chocolate may be a factor for heartburn in some people because theobromine may affect the esophageal sphincter muscle in a way that permits stomach acids to enter the esophagus.
Animals
Theobromine is the reason chocolate is poisonous to dogs. Dogs and other animals that metabolize theobromine (found in chocolate) more slowly
The median lethal dose of theobromine for dogs is ; therefore, a dog would need to consume a minimum of of the most theobromine-rich () dark chocolate, or a maximum of (of theobromine-rich milk chocolate), to have a 50% chance of receiving a lethal dose. However, even of milk chocolate may induce vomiting and diarrhea.
The same risk is reported for cats as well,
See also
