Oleum Anisi, B.P., Oil of Anise.
Oil of anise is obtained by distillation from the fruit of Pimpinella Anisum, Linn. (N.O. Umbelliferae), cultivated in nearly all parts of the world, and from the star anise, Illicium verum, Hook. f. (N.O. Magnoliaceae), indigenous and cultivated in Southern China and Tonkin. The greater part of the commercial oil comes from the latter plant. Oil of anise is also official in the U.S.P. It occurs as a colourless or pale yellow, highly refractive liquid, having a characteristic aromatic odour and a sweet aromatic taste. It solidifies to a white crystalline mass on cooling to 10°, remelting at 15° to 19°. Specific gravity, 0.975 to 0.990 at 20° (0.975 to 0.988 at 25°). Rotation, usually 0° to -2°; occasionally slightly dextrorotatory. The oil can be cooled considerably below its freezing-point without becoming solid, and can be kept so for a long time if undisturbed, but slight agitation, or the introduction of a minute crystal of anethol, sets up immediate solidification of the entire mass. Exposure to the air causes polymerisation and oxidation, with formation of anisic aldehyde, C8H8O2, and anisic acid; the solidifying point becomes lowered, the specific gravity increases and the oil becomes more soluble in alcohol. The oil is subject to much adulteration, especially with petroleum, also with fennel oil, the liquid portion of the oil obtained in the manufacture of anethol, turpentine oil, alcohol, and fatty oils. The best criterion of purity is the melting-point, which is usually about 17°. It is said that the two anise oils may be distinguished by treating with a saturated solution of hydrochloric acid gas in absolute alcohol, the oil of P. Anisum yielding a blue colouration, and that of Illicium verum a yellow to brownish colour, but the test does not appear to be entirely satisfactory. The oils differ slightly in odour and flavour.
Soluble in alcohol (1 in 3). The presence of 5 per cent. of petroleum, however, diminishes the solubility to 1 in 10 or more.
Constituents.—The characteristic properties of the oil are due to anethol, C10H12O, solid at ordinary temperatures, and present to the extent of 80 to 90 per cent. It occurs in the form of white, crystalline laminae, melting at 21° to a colourless, refractive, optically inactive, liquid, having the characteristic odour and taste of anise. Specific gravity, 0.986 at 25°. Boiling-point, 232°. Another constituent is methyl chavicol, isomeric with anethol, an optically inactive liquid, having the odour, but not the sweet taste, of anise. These two constituents, together with traces of oxidation products, anisic aldehyde and anisic acid, are the only constituents of proved identity in the pimpinella oil. In the star-anise, however, d-pinene, l-phellandrene, the ethyl ester of hydroquinone, and probably safrol, occur, besides those already mentioned.
Action and Uses.—Oil of anise is employed as an aromatic carminative to relieve flatulence. The oil may be administered on sugar or as Spiritus or Elixir Anisi. It is a mild expectorant, and is an ingredient of simple cough lozenges, often in combination with liquorice. As a flavouring agent it is combined with the oils of gaultheria and peppermint in aromatic mouth washes.
Dose.—¼ to 2 decimils (0.025 to 0.2 milliliters) (1 to 3 minims).
- Aqua Anisi, U.S.P.—ANISE WATER, U.S.P.
- Oil of anise, 0.2; purified talc, 1.5; distilled water, to 100. Average dose.—16 mils (4 fluid drachms).
- Aqua Anisi Concentrata, B.P.C.—CONCENTRATED ANISE WATER.
- One part of this solution corresponds to 40 parts of anise water.
- Elixir Anisi, B.P.C.—ELIXIR OF ANISE. Syn.—ANISEED CORDIAL.
- Oil of anise, 0.3; oil of fennel, 0.05; spirit of bitter almond, 1.25; with alcohol, syrup, and distilled water, to 100. Used as a carminative arid flavouring agent. Dose.—2 to 8 mils (½ to 2 fluid drachms).
- Elixir Anisi, C.F.—Similar to B.P.C., but made with anethol and deodorised alcohol.
- Spiritus Anisi, B.P.—SPIRIT OF ANISE.
- Oil of anise, 10; alcohol, sufficient to produce 100. Spirit of anise is used chiefly as a flavouring agent. Dose.—3 to 12 decimils (0.3 to 1.2 milliliters) (5 to 20 minims).
- Spiritus Anisi, U.S.P.—Similar to B.P., but made with alcohol (95 per cent.).