Oleum Anisi (U. S. P.)—Oil of Anise.
"A volatile oil distilled from anise. It should be kept in well-stoppered bottles protected from light, and, if it has separated into a liquid and a solid portion, it should be completely liquefied by warming before being dispensed"—(U. S. P.).
Source and Chemical Composition.—This oil is prepared by distilling anise seed, from Pimpinella anisum, Linné, with water. The Russian seeds are now mostly used; they yield, according to Schimmel & Co. (Reports, April, 1897), from 2.4 to 3.2 per cent of oil; Italian fruit (Bolognese) yielded as high as 3.5 per cent. Over 90 per cent of the oil consists of anethol (para-methoxy-propenyl-benzol, C10H12O, or C6H4[OCH3].CH:CH.CH3), which is the essential aromatic constituent of the oil. It was obtained synthetically, in 1877, by Perkin. It is a snow-white, crystallizable body, of sweet taste, melts at 21.5° C. (69.8° F.), and is optically inactive. The liquid constituent of anise oil is methyl-chavicol, an isomer of anethol. Both anethol and methyl-chavicol also occur in the oil of star-anise (Illicium verum) (Schimmel's Report, Oct., 1895); anethol is also found in fennel oil (Cahours, 1841). In oil of star-anise, dextro-pinene and laevo-phellandrene were also found.
Description and Tests.—The U. S. P. describes the oil as follows: "A colorless or pale-yellow, thin, and strongly refractive liquid, having the characteristic odor of anise, and a sweetish, mildly aromatic taste. Specific gravity, about 0.980 to 0.990 at 17° C. (62.6° F.), increasing with age. At a low temperature, usually between 10° and 15° C. (50° and 59° F.), it solidifies to a white, crystalline mass. Soluble in an equal volume of alcohol to a clear solution (absence of most fixed oils and oil of turpentine). This solution is neutral to litmus paper, and should not assume a blue or brownish color on the addition of a drop of ferric chloride T.S. (absence of some volatile oils containing phenols). When the oil is dropped into water, without agitation, it should not produce a milky turbidity (absence of alcohol)"—(U. S. P.).
Action, Medical Uses, and Dosage.—Both oil of anise and oil of star-anise, are carminative and antispasmodic, and especially adapted to flatulency and colic of infants. They likewise, in connection with aqua ammoniae, ammonium chloride, or ammonium carbonate, afford relief in spasmodic cough. The dose is from 5 to 10 drops. Ruschenberger states that the offensive odor of the tersulphides in solutions or ointments is removed or completely covered by the presence of oil of anise. Oil of anise is an ingredient of paregoric and other well-known preparations.
Related Oil.—OIL OF ANISE BARK. From Madagascar; botanical source unknown, but the bark closely resembles the Massoi bark, and yields 3.5 per cent of essential oil. The oil is pale-yellow, spicy and feebly sweet to the taste, and has an odor suggestive of safrol. Density, 0.969. It contains chiefly Eykman's methyl-chavicol (CH3O.C6H4.CH2.CH.CH2), the fluid anethol isomeric with ordinary anethol, of which it also contains a small proportion (Schimmel & Co.'s Report, April, 1892, p. 53).