Oleoresines, Extraits etheres, Fr.; Oelharze, Aetherische Extrakte, G.
The oleoresins, as a class of preparations, were introduced into the U. S. Pharmacopoeia at the revision of 1860, having been previously classed with the Fluidextracts. Their peculiarity is that they consist of principles which, when extracted by means of ether, alcohol, or acetone, retain a liquid or semi-liquid state upon the evaporation of the menstruum, and at the same time have the property of self-preservation, differing from the fluidextracts in not having a definite relation of strength to the drug. They consist chiefly, as their name implies, of oil, either fixed or volatile, holding resin and sometimes other active matter in solution. Their preparation is very simple, consisting in the exhaustion of the drug with acetone, alcohol or ether by means of percolation, and the subsequent evaporation of the menstruum. In consequence of the great volatility of the solvent, it may in great measure be recovered by distillation, thus very materially diminishing the costliness of the process. It is proper not to continue the heat necessary for the recovery of the solvent by distillation until the whole of the solvent is driven over, lest, towards the close, a portion of the volatile matters also should pass, and the strength of the oleoresin be impaired. Hence in every instance the last portions of the menstruum are allowed to separate by spontaneous evaporation. Petroleum benzin has been proposed as a substitute for other solvents in these preparations, but should not be permitted to supersede them until officially sanctioned. It is difficult, if not impossible, to remove the last traces of this solvent without loss of volatile oil. Acetone replaced ether in most of the formulas of the U. S. P. VIII on account of economy, but as ether is again the cheaper solvent because of the use of denatured alcohol in its manufacture, it is again officially directed in the U. S. P. IX. Oleoresin of cubeb is made with alcohol.