Oleum Pimentae, B.P. Oil of Pimento.

Related entries: Pimento - Oil of Pimento Leaves

Oil of pimento, or allspice oil, is obtained by distillation from the dried, full-grown, unripe fruit of Pimenta officinalis, Lindl. (N.O. Myrtaceae), a tree which is indigenous to the West Indies, Mexico, and South America, and cultivated largely in Central America and Jamaica. It is also official in the U.S.P. It occurs as a yellow or yellowish-red liquid, becoming gradually darker on keeping, and having a pleasant aromatic odour somewhat similar to that of oil of cloves, and a pungent, spicy taste. Specific gravity, 1.030 to 1.050 (B.P., not below 1.040), (1.025 to 1.045 at 25°); rotation, laevorotatory, never exceeding -4°, more usually about -2°.

Soluble in all proportions of alcohol; in 70 per cent. alcohol (1 in 2), forming a clear solution; in 60 per cent. alcohol (1 in 50).

Constituents.—The chief constituent of the oil is the phenol eugenol, C₁₀H₁₂O₁₁ which is present to the extent of 60 to 75 per cent., and a sesquiterpene, the exact nature of which has not yet been ascertained. The clove-like odour of the oil is doubtless due to the eugenol, but the characteristic odour is due to some other substance or substances as yet unknown. A certain amount of resin is also present, but the oil has not been fully investigated. The specific gravity to some extent indicates the amount of eugenol present. If lower than 1.030, it may be assumed that some eugenol has been removed, or that the oil has been adulterated with substances having a lower specific gravity than that of eugenol. The eugenol may be determined by shaking the oil with solution of potassium hydroxide, as described under Oleum Caryophylli, and measuring the residual oily layer, or by Thom's process, a method based on the conversion of eugenol into benzoyl eugenol. At least 65 per cent. of eugenol should be present (U.S.P.). All alcoholic solution gives with very dilute solution of ferric chloride a fine indigo blue colouration. On shaking the oil with an equal volume of strong solution of ammonia, it is converted into a semi-solid mass. This reaction and the previous one are also given by oil of cloves.

Action and Uses.—Oil of pimento resembles oil of cloves in its properties, and. is used as a carminative to the intestinal tract and as an adjuvant to aperient medicines.

Dose.—½ to 2 decimils (0.05 to 0.2 milliliters) (1 to 3 minims).

PREPARATION.

Aqua Pimentae Concentrata, B.P.C.—CONCENTRATED PIMENTO WATER.

One part of this solution corresponds to 40 parts of pimento water.

The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.