Theobromatis Semina, Theobroma Seeds. Theobromina, Theobromine.
Theobroma seeds are the product of Theobroma Cacao, Linn. (N.O. Sterculiaceae), a tree cultivated in tropical America, Java, Ceylon, West Indies, etc. The fruit contains a number of seeds embedded in a scanty mucilaginous pulp. After separation from the pulp, they are allowed to undergo a species of fermentation, and are then dried. During fermentation, the seeds acquire a reddish-brown colour, and the taste, at first astringent and bitter, becomes mild and oily. The seeds are about 2.5 centimetres in length, and flattened-ovoid in shape. The testa is reddish-brown, thin, brittle, and easily separable. The kernel is composed of two irregularly folded, chocolate-coloured cotyledons, readily breaking into small, angular fragments (cocoa nibs). The taste is agreeable, but oily. Theobroma powder or cocoa is prepared from the seeds by depriving the kernels of fat and grinding them to powder, the product being afterwards treated so as to render it readily diffusible in water. As found in commerce, cocoa is a brown powder, which should contain but little fat, starch, or sugar. It is sometimes flavoured, and should diffuse readily when mixed with boiling water. Theobroma paste, or chocolate, is a mixture of the finely powdered kernels with sugar, and vanilla or other suitable flavouring. It is a sweet reddish-brown paste with an agreeable flavour, containing about 25 per cent. of oil of theobroma, and not more than 50 per cent. of sugar, without starch in quantity, or gum, or other addition.
Constituents.—The kernels contain about 2 per cent. of theobromine, and 40 to 60 per cent. of solid fat. The greater portion of the fat can be separated by pressing the heated seeds, and constitutes cacao butter or oil of theobroma; the pressed kernels ground to powder form the basis of the cocoa essences of commerce. The shells contain about 1 per cent. of theobromine, together with mucilage, etc.
Action and Uses.—Cocoa powder and theobroma paste (chocolate) prepared therefrom, are used in the preparation of certain tablets and lozenges. Its agreeable flavour and preservative action also render it useful as a basis for administering erythrol tetranitrate, methylacetanilide, menthol, pepsin, santonin, bismuth preparations, and such alkaloids as apomorphine, caffeine, and cocaine.
C7H8N4O2 = 180.104.
Theobromine, or dimethylxanthine, C5H2(CH3)2N4O2, is an alkaloid contained in the seeds of Theobroma Cacao, Linn. (N.O. Sterculiaceae). It is a lower homologue of caffeine (trimethylxanthine or methyltheobromine), and is said not to be present as theobromine in the unfermented seeds, but to develop during the process of curing by the splitting up of a glucoside, dextrose and cacao red being the other products. It may be prepared by boiling the powdered beans with water, filtering and pressing, precipitating tannins and colouring matter with lead acetate, filtering, removing lead with sulphuric, acid, concentrating the solution, adding magnesia, evaporating to dryness, extracting the residue with alcohol, and purifying by recrystallisation from water; or by mixing the powdered cacao, deprived of oil, with half its weight of freshly prepared slaked lime, and boiling with 80 per cent. alcohol in a reflux condenser. On cooling the almost colourless filtrate, part of the theobromine separates as a white, crystalline powder; the remainder is obtained by distilling off the alcohol, and is purified by recrystallisation. Theobromine occurs in the form of an odourless, white crystalline powder, in rhombic needles, having a neutral reaction, and a taste at first slightly bitter, but gradually becoming more so. It sublimes at 290° without fusion or decomposition. It combines readily with bases; with acids it combines only slowly; even the mineral acid salts give up to water, and alcohol, or on warming, a part or all of the acid. The most characteristic test for theobromine, and that by which it may most readily be distinguished from and separated from caffeine is the silver test. If 1 decigram be dissolved in a mixture of 1 mil of nitric acid and 2 mils of water, the solution becomes cloudy on the addition of 10 mils of a 10 per cent. solution of silver nitrate, but clears on warming, and crystallises on cooling. If theobromine, as formed in the previous test, be heated to 100° with methyl iodide, it is converted into methyl-theobromine or xanthine, which is identical with caffeine or theine. If 1 gramme of theobromine be mixed with 4 mils of water, and just enough solution of sodium hydroxide added to form a clear solution, and then shaken with 10 mils of chloroform, the latter on evaporation should riot leave a residue weighing more than 5 milligrams (absence of caffeine). If bromine water be added to a solution of theobromine in hydrochloric acid, and excess of bromine driven off, the solution turns blue on the addition of a trace of ferrous sulphate in solution and a few drops of ammonia. On evaporating a mixture of theobromine and chlorine water to dryness, and then adding ammonia, a purple colour is developed. The alkali hydroxides and ammonia give precipitates soluble in excess, forming salts. Mercuric chloride precipitates it from strong solutions in crystalline form, but gives only a cloud at 1 in 3000. Potassio-mercuric iodide has no effect; tannic acid produces a cloud in dilute solutions, and so does bismuth-potassium iodide; picric acid has no effect.
Soluble in water (1 in 1700), boiling water (1 in 55), alcohol (1 in 1400), boiling alcohol (1 in 50); very difficultly soluble in ether, less difficultly in amyl alcohol; in boiling chloroform (1 in about 100 parts); scarcely soluble in benzene; insoluble in petroleum ether.
Action and Uses.—Theobromine resembles caffeine in its action (see Caffeina) with the difference that while its effect upon the central nervous system is very much less than that of caffeine, its action on muscle, the kidneys, and the heart is more pronounced. It is used principally for its diuretic effect due to stimulation of the renal epithelium; this is produced more certainly and to a greater extent than with caffeine, and the nervous symptoms produced by the latter, vaso-constriction, increased respiration, and cerebral excitement are absent. It is especially useful when there is an accumulation of fluid in the body resulting from cardiac failure, in which case it is often prescribed with digitalis to relieve dilatation of the heart. Its action seems to warrant its employment in high blood pressure, because, whilst stimulating the heart like caffeine, it dilates blood vessels like the nitrites; it is contra-indicated in acute nephritis, since it is obviously wrong to make a diseased organ do more work. It is also employed in dropsy of renal or hepatic origin. In large doses it may cause nausea and loss of appetite. Theobromine is best administered in powders or cachets. Pills may be prepared with glycerin of tragacanth. Theophylline—also a dimethylxanthine—has a more marked diuretic action even than theobromine, but is prone to cause digestive disturbance. A synthetic theophylline has been prepared and sold under the trade-name Theocin. Theophylline-sodium (theocin-sodium) acetate is used as a diuretic, in doses of 1 to 3 decigrams (1 ½ to 4 grains) thrice daily. It is more soluble than theophylline, and is less liable to cause unpleasant effects. Theobromine-sodium sodio-iodide is sold under the trade-name Eustenin. It is a white, somewhat deliquescent powder, used in aneurism and arterio-sclerosis; dose, ½ to 1 gramme (8 to 15 grains). It is best prescribed in mixture form. Theobromine-sodium sodio-formate is a white powder soluble in water. It is used as a diuretic; dose, ½ to 1 gramme (8 to 15 grains). Theobromine-sodium sodio-acetate is known under the trade-name Agurin. It occurs as a white, deliquescent powder, soluble in water (1 in 2), and is used as a diuretic, being given in doses of 5 to 10 decigrams (8 to 15 grains) in mixtures. Dose.—3 to 6 decigrams (5 to 10 grains).