Fractionation of Irradiated Cholesterol

Abstract

One of us recently reported 1 that cholesterol, as a result of exposure in air to light from the mercury-vapor quartz lamp, reacted differently from the untreated cholesterol towards a reagent consisting of aniline and concentrated hydrochloric acid. With the aid of this color reaction, fractionation of irradiated cholesterol was undertaken. It was hoped that in this way an antirachitically active fraction might be obtained.

After repeatedly recrystallizing irradiated cholesterol, it gave a negative color reaction, while the mother liquor, from the first recrystallization, gave a more intense reaction than did the irradiated cholesterol itself. The mother liquor was concentrated by evaporation and filtered. The final filtrate was yellow, removal of the remaining solvents on a water bath left a yellow oil. Recrystallization of purified cholesterol gave no such product. For convenience, it will be referred to as “U. V. oil of cholesterol” until a more suitable name is proposed.

The yield of crude oil was about 10 per cent when the cholesterol was irradiated for two hours, and about 5 per cent when irradiated for one hour. The irradiation was performed in air at a distance of 18 inches, using a Hanovia lamp. The cholesterol was removed by the digitonin precipitation method. About 40 per cent of the crude oil was recovered as cholesterol-free oil.

The color reactions usually used for the detection of cholesterol were tried on the cholesterol-free oil. With 1 mg. of this oil, a positive Salkowski test was obtained; with 1 mg. of purified cholesterol the upper layer was yellow, and very little green was obtained in the lower layer. Apparently the Salkowski 2 test is not given by purified cholesterol in small quantities while it is given intensely by one or more of its derivatives.