A Note on the Assay of Ascaridole in Castor Oil Solution

Abstract

OIL of chenopodium diluted with 19 parts of castor oil, with the official title of solution of chenopodiuml is used as a veterinary anthelmintic and owes its therapeutic activity to the ascaridole present. Apart from the desirability of estimating the active ingredient rather than an added constituent of a galenical, the importance of the determination of ascaridole in solution of chenopodium lies in the need to standardise the ascaridole content within narrow limits. This close assessment is necessary because it has been asserted that the therapeutic dose is close to the toxic dose for certain animals.Since the B.P. assay of ascaridole in chenopodium oil is an empirical method requiring strict adherence to detail the determination is inapplicable with the considerable modification of conditions necessitated by the presence of the castor oil and the low concentration of ascaridole.Preliminary experiments with more obvious methods of approach to the problem were all abortive, the recovery of ascaridole being very low. These determinations included (a) distillation of the oil of chenopodium from water in the B.P. apparatus for the determination of volatile oils in drugs, followed by a determination of ascaridole on the recovered oil by the B.P. method, (b) direct extraction of the oil of chenopodium from the mixture with 70 per cent. acetic acid and determination by the B.P. method and (c) direct titration of the mixture, in ethanol (96 per cent.) by titanous chloride solution (Paget2).The possibility of co-distillation with a water-miscible solvent possessing a boiling point slightly higher than that of ascaridole was commendable, a glycol being an obvious choice. Early trials were encouraging since good recoveries of ascaridole were achieved but a large number of analyses showed that small but significant under-recoveries of ascaridole (of the order of 10 per cent.) were obtained. These low results were traced to losses occurring during evaporation of the solvent used to extract the ascaridole from the distillate after dilution with water. Further experiments showed that these losses could be avoided if the solvent were evaporated in the presence of 90 per cent. acetic acid, the acid solution being suitable for direct application of the B.P. method; the method described below gave satisfactory results.To 50 g., accurately weighed, of a 5 per cent. solution of oil of chenopodium in castor oil placed in a 500-ml. Claisen flask, add 50 ml. of ethylene glycol. Distil at a pressure of about 0.5 mm. Hg. (using glass wool and porous pot to prevent bumping) until the contents of the distillation flask are clear. Transfer the distillate to a separating funnel and dilute 60

Review - Essential Oils and Related Products

“…Maruyama (78) investigated the polarographic determination of ascaridole and reported an accuracy within ± 1 %. Garratt and Phipers (52) assayed ascaridole in castor oil solutions of chenopodium oil by a distillation with ethylene glycol, separation of the oil from the distillate, and final determination of ascaridole by the official method of the British Pharmacopoeia.…”