Oleum Theobromatis, B.P. Oil of Theobroma.
Oil of theobroma is a solid fat obtained by expression from the crushed seeds of Theobroma Cacao, Linn. (N.O. Sterculiaceae), a native of Mexico, South America, and the West Indies. It is also official in the U.S.P. It is obtained chiefly as a by-product in the manufacture of cocoa. Oil of theobroma occurs as a concrete fat or fixed oil, usually in oblong cakes which break with a smooth fracture, showing indications of crystalline structure, yellowish-white or pale yellow when fresh, but becoming white on keeping; the odour resembles that of chocolate and the taste is bland and agreeable. It becomes rancid on keeping, but the tendency to do so is not so great as in the case of most other fats. Specific gravity, 0.990 to 0.998 (0.970 to 0.976 at 25°). It is somewhat brittle at ordinary temperatures, softens at 26.6°, and melts between 31° and 34°. Saponification value, 188 to 195. Iodine value, 33 to 38. When the oil has been recently melted, the specific gravity on solidification is lower than that stated, owing apparently to some molecular change caused by the application of heat; these effects do not pass entirely away at once, and the specific gravity only attains its higher and final value after some time has elapsed. The adulterants are paraffin, stearin, wax, coconut oil, tallow, suet, or other fats. Coconut oil, which is largely used as an adulterant, contains much larger proportions of fatty acids, considerably increases the saponification value, and reduces the iodine value. The following test will show the absence of other fats:—On dissolving 1 mil in 3 mils of ether and exposing the solution to a temperature of 0°, the liquid will not become turbid, nor deposit a granular mass in less than three minutes, while after congealing, a clear solution should result on warming the mass to 15.5°. For this test a strong, corked, test-tube should be used. The manner in which the crystallisation of the fat from ether occurs should be noted. Cacao butter separates in tufts at the bottom and sides of the tube, whilst in the presence of 5 per cent. of tallow the crystals separate in flakes.
Readily soluble in ether, chloroform, benzene, petroleum ether; in boiling absolute alcohol (1 in 5); insoluble in alcohol (distinction from coconut oil).
Constituents.—The chief constituents of the fat are the glycerides of stearic (about 40 per cent.), palmitic, and oleic acids, together with small quantities of the glycerides of arachidic, linoleic and other fatty acids.
Action and Uses.—Oil of theobroma is employed in pharmacy chiefly for the preparation of suppositories, pessaries, and bougies. Samples of a low melting-point are preferable for this purpose, as various medicaments—especially metallic salts and substances containing tannin—raise the melting-point of the mass. Oil of theobroma is sometimes an ingredient of emollient ointments, and it is rubbed on the skin as a lubricant in massage. It is customary to prepare suppositories, pessaries, and bougies with an oil of theobroma basis, in the absence of any indication to the contrary.
- Emulsio Theobromatis, B.P.C.—THEOBROMA EMULSION. 1 in 4.
- Used in the preparation of certain compressed tablets. Where the presence of soap is undesirable, 15 of gum acacia may be substituted. The substance to be compressed is reduced to very fine powder, and triturated with sufficient of the emulsion to make it coherent, but not so damp as to adhere to the meshes when shaken or gently rubbed through a No. 20 or No. 30 sieve. After being sifted, the mixture is dried by exposing it to the air; or, when the nature of the substance permits, by the application of gentle heat. When dry, it may be compressed into tablets.
- Liquor Theobromatis Aethereus, B.P.C.—ETHEREAL SOLUTION OF THEOBROMA.
- Oil of theobroma, 16.5; ether, sufficient to produce 100. An equal volume of alcohol is added to this preparation when it is required for use. Ethereal solution of theobroma is used as a tablet excipient for substances which form masses of a pill-like nature with water, such as aloes and extract of cascara. Two modifications of this formula are recommended for use on occasion. (1) The use of weaker alcohol when the granulation produced with the stronger alcohol is imperfect, in which case the ethereal solution of theobroma and alcohol should be added separately, as in the case of Tablettae Opii. (2) Reduction of the proportion of alcohol when an equal volume would produce a sticky mass, as in the case of Tablettae Cascarae Sagradae. In granulating with ethereal solution of theobroma the excipient should be added all at once to the substance or mixture contained in a mortar, trituration accomplished as quickly as possible, the mass passed through a No. 20 sieve and set aside to dry.