Theobromine, also known as xantheose, is the principal alkaloid of Theobroma cacao (cacao plant).[4] Theobromine is slightly water-soluble (330 mg/L) with a bitter taste.[5] In industry, theobromine is used as an additive and precursor to some cosmetics.[4] 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.[5]
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.[13] That name in turn is made up of the Greek roots theo ("god") and broma ("food"), meaning "food of the gods".[14]
Despite its name, the compound contains no bromine, which is based on Greek bromos ("stench").
Sources
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.[15]
There are approximately 60 milligrams (1 grain) of theobromine in 28 grams (1 oz) of milk chocolate,[16] while the same amount of dark chocolate contains about 200 milligrams (3 grains).[17] Cocoa beans naturally contain approximately 1% theobromine.[18]
Plant species and components with substantial amounts of theobromine are:[19][20]
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.[25]
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.[26]
In the liver, theobromine is metabolized into xanthine and subsequently into methyluric acid.[27] Important enzymes include CYP1A2 and CYP2E1.[28] The elimination half life of theobromine is between 6 and 8 hours.[1][2]
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.[29]
Theobromine has no significant stimulant effect on the human central nervous system.[4] It is a bronchodilator and causes relaxation of vascular smooth muscle.[4] It is not currently used as a prescription drug.[5] 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.[33]
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.[34]
Animals
Theobromine is the reason chocolate is poisonous to dogs. Dogs and other animals that metabolize theobromine (found in chocolate) more slowly[35] can succumb to theobromine poisoning from as little as 50 g (1.8 oz) of milk chocolate for a smaller dog and 400 g (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 (about 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.[citation needed]
The median lethal dose of theobromine for dogs is 100–200 mg/kg (0.0016–0.0032 oz/lb); therefore, a 10 kg (22 lb) dog would need to consume a minimum of 200 g (7.1 oz) of the most theobromine-rich (5 g/kg (0.080 oz/lb)) dark chocolate, or a maximum of 1 kg (2.2 lb) (of theobromine-rich milk chocolate), to have a 50% chance of receiving a lethal dose. However, even 40 g (1.4 oz) of milk chocolate may induce vomiting and diarrhea.[36]
The same risk is reported for cats as well,[37] although cats are less likely to ingest sweet food, as cats lack sweet taste receptors.[38] 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.[39] Although not common, the effects of theobromine poisoning can be fatal.[38]
^ abDrouillard DD, Vesell ES, Dvorchik BH (March 1978). "Studies on theobromine disposition in normal subjects. Alterations induced by dietary abstention from or exposure to methylxanthines". Clinical Pharmacology and Therapeutics. 23 (3): 296–302. doi:10.1002/cpt1978233296. PMID627135. S2CID10519385.
^Kuribara H, Tadokoro S (April 1992). "Behavioral effects of cocoa and its main active compound theobromine: evaluation by ambulatory activity and discrete avoidance in mice". Arukoru Kenkyu to Yakubutsu Izon = Japanese Journal of Alcohol Studies & Drug Dependence. 27 (2): 168–179. PMID1586288.
^Craig WJ, Nguyen TT (1984). "Caffeine and theobromine levels in cocoa and carob products". Journal of Food Science. 49 (1): 302–303. doi:10.1111/j.1365-2621.1984.tb13737.x. 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.
^Mumford GK, Benowitz NL, Evans SM, Kaminski BJ, Preston KL, Sannerud CA, et al. (1 December 1996). "Absorption rate of methylxanthines following capsules, cola and chocolate". European Journal of Clinical Pharmacology. 51 (3–4): 319–325. doi:10.1007/s002280050205. PMID9010706. S2CID8405909.