Theobromine
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Template:Chembox Theobromine, also known as xantheose, is the principal alkaloid of Theobroma cacao (cacao plant).<ref name="pubchem">Template:Cite web</ref> Theobromine is slightly water-soluble (330 mg/L) with a bitter taste.<ref name=Hbk>Template:Cite book</ref> In industry, theobromine is used as an additive and precursor to some cosmetics.<ref name=pubchem/> It is found in chocolate, as well as in a number of other foods, including tea (Camellia sinensis), some American hollies (yaupon and guayusa) and the kola nut. It is a white or colourless solid, but commercial samples can appear yellowish.<ref name=Hbk/>
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
[edit]Theobromine is a flat molecule,<ref name=Acta>Template:Cite journal</ref> a derivative of purine and an isomer of theophylline.<ref>Template:Cite web</ref> It is also classified as a dimethyl xanthine.<ref name=Hbk/><ref name="envbeh-p200">Template:Cite book</ref> Related compounds include theophylline, caffeine, paraxanthine, and 7-methylxanthine, each of which differ in the number or placement of the methyl groups.<ref name=Hbk/>
History
[edit]Theobromine was first discovered in 1841<ref>Template:Cite book</ref> in cacao beans by the chemist A. Woskresensky.<ref>Template:Cite journal</ref> Synthesis of theobromine from xanthine was first reported in 1882 by Hermann Emil Fischer.<ref name="historicalchemistry">Template:Cite book</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
Etymology
[edit]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.<ref name="dict-ine">Template:Cite book</ref> That name in turn is made up of the Greek roots theo ("god") and broma ("food"), meaning "food of the gods".<ref name="worldofcaffeine">Template:Cite book (note: the book incorrectly states that the name "theobroma" is derived from Latin)</ref>
Despite its name, the compound contains no bromine, which is based on Greek bromos ("stench").
Sources
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Theobromine is the primary alkaloid found in cocoa and chocolate. Cocoa butter only contains trace amounts of theobromine. There are usually higher concentrations in dark than in milk chocolate.<ref name="AmerMed_cocoa">Template:Cite web</ref>
There are approximately Template:Convert of theobromine in Template:Convert of milk chocolate,<ref name="USDA db milk chocolate entry">Template:Cite web</ref> while the same amount of dark chocolate contains about Template:Convert.<ref name="USDA db dark chocolate entry">Template:Cite web</ref> Cocoa beans naturally contain approximately 1% theobromine.<ref>Template:Cite journal</ref>
Plant species and components with substantial amounts of theobromine are:<ref name="arsgrin-theobromine">Template:Cite web</ref><ref name=":4">Template:Cite journal</ref>
- Theobroma cacao – seed and seed coat
- Theobroma bicolor – seed coat
- Ilex paraguariensis – leaf
- Ilex guayusa – leaf
- Ilex vomitoria – leaf
- Camellia sinensis – leaf
Theobromine can also be found in trace amounts in the kola nut, the guarana berry, yerba mate (Ilex paraguariensis),<ref>Template:Cite journal</ref> and the tea plant.<ref name="culthistplants">Template:Cite book</ref>
The mean theobromine concentrations in cocoa and carob products are:<ref>Template:Cite web</ref><ref name=Craig1984>Template:Cite journal</ref>
| 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 |
| Chocolate milks | 22.6 mg |
| Carob products | 0.00–50.4 mg |
Biosynthesis
[edit]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.<ref>Template:Cite book</ref>
Pharmacology
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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.<ref name="pharmgkb">Template:Cite web</ref>
In the liver, theobromine is metabolized into xanthine and subsequently into methyluric acid.<ref>Template:Cite journal</ref> Important enzymes include CYP1A2 and CYP2E1.<ref>Template:Cite journal</ref> The elimination half life of theobromine is between 6 and 8 hours.<ref name="halflife1" /><ref name="halflife2" />
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.<ref>Template:Cite journal</ref>
The primary mechanism of action for theobromine inside the body is inhibition of adenosine receptors.<ref name=Hbk/> Its effect as a phosphodiesterase inhibitor<ref name="PDEs-Essayan">Template:Cite journal</ref> is thought to be small.<ref name=Hbk/>
Effects
[edit]Humans
[edit]Theobromine is a heart stimulator and diuretic but has no significant stimulant effect on the human central nervous system.<ref name=pubchem/> It is a bronchodilator and causes relaxation of vascular smooth muscle.<ref name=pubchem/> It is available as a prescription drug in South Korea.<ref>Template:Cite web</ref> The amount of theobromine found in chocolate is small enough that chocolate can, in general, be safely consumed by humans.
Compared with caffeine, theobromine is weaker in both its inhibition of cyclic nucleotide phosphodiesterases and its antagonism of adenosine receptors.<ref name=pubchem/><ref name="therapeutics">Template:Cite book</ref> The potential phosphodiesterase inhibitory effect of theobromine is seen only at amounts much higher than what people normally would consume in a typical diet including chocolate.<ref>Template:Cite web</ref>
Toxicity
[edit]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.<ref>Template:Cite web</ref>
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.<ref name="Latif">Template:Cite journal</ref>
Animals
[edit]Theobromine is the reason chocolate is poisonous to dogs. Dogs and other animals that metabolize theobromine (found in chocolate) more slowly<ref>Template:Cite web</ref> can succumb to theobromine poisoning from as little as Template:Cvt of milk chocolate for a smaller dog and Template:Cvt, or around nine Template:Convert small milk chocolate bars, for an average-sized dog. The concentration of theobromine in dark chocolates (about Template:Cvt) is up to 10 times that of milk chocolate (Template:Cvt), meaning dark chocolate is far more toxic to dogs per unit weight or volume than milk chocolate.Template:Cn
The median lethal dose of theobromine for dogs is Template:Cvt; therefore, a Template:Cvt dog would need to consume a minimum of Template:Cvt of the most theobromine-rich (Template:Cvt) dark chocolate, or a maximum of Template:Cvt (of theobromine-rich milk chocolate), to have a 50% chance of receiving a lethal dose. However, even Template:Cvt of milk chocolate may induce vomiting and diarrhea.<ref>Template:Cite web</ref>
The same risk is reported for cats as well,<ref>Template:Cite web</ref> although cats are less likely to ingest sweet food, as cats lack sweet taste receptors.<ref name=wired>Template:Cite magazine</ref> 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.<ref name="healthwatchcanines">Template:Cite news</ref> Although not common, the effects of theobromine poisoning can be fatal.<ref name="wired" />
See also
[edit]References
[edit]Template:Commons category Template:Chocolate Template:Diuretics Template:Asthma and copd rx Template:Adenosinergics Template:Phosphodiesterase inhibitors