Pharmaceutical Applications of Inclusion Compounds. II

Extractive Crystallization of Ascaridol by Thiourea Adduct Formation

Abstract

Addition of methanolic solution of thiourea to benzene solution of chenopodium oil results in precipitation of needle crystals, which was found from X-ray diffraction and infrared spectrum to be the so-called inclusion compound of rhombohedral crystals. Extraction of the guest molecule with ether leaves a pure ascaridol and the original crystalline substance is an adduct of 1 mole of ascaridol and 4.6 moles of thiourea. This is a useful method for getting the effective component from chenopodium oil in crystalline form and the method is also used for purification of ascaridol. It has the advantage of rendering ascaridol into convenient form for preparations. Components other than ascaridol contained in chenopodium oil hardly form adduct with thiourea and actually, the infrared spectrum of ascaridol obtained from the crystalline adduct exhibits no absorption due to impurities. When the said crystal is heated above 70° or placed in vacuum, ascaridol liberates from the crystal, leaving the original rhombic crystal of thiourea.