Contaminating Substances as a Factor in the Activation of Cholesterol by Irradiation.

Abstract

In a recent communication 1 we reported the effects of irradiation on a large number of cholesterol derivatives prepared by one of us (Windaus). Among other derivatives which were tested biologically, and which failed to be activated, was a phytosterol extracted from rapeseed oil. It had been expected that this preparation, would develop antirachitic properties after subjection to the rays from the mercury-vapor lamp. This failure indicated that activation in general may be due to some contaminating substance rather than to an alteration in the cholesterol itself.

Some previous experiences had suggested a similar interpretation—for example, the slight changes in physical constants which came about in cholesterol following irradiation, and again the fact that activated cholesterol could be fractionated into an active and an inactive fraction by means of liquid ammonia². The ammonia-soluble fraction, representing somewhat less than 4 per cent of the original cholesterol, was found to have antirachitic potency.

A preparation of cholesterol was purified by means of being separated twice as the dibromide and subsequently recrystallized. This preparation failled to be activated by ultra-violet rays. 0. Rosenheirn has communicated to one of us (Windaus) that he has had a similar negative result with brolminated (cholesteroll. Furthermore, it did not give the characteristic absorption spectrum of ordinary cholesterol, nor did it show a decrease in absorption following irradiation, a phenomenon which takes place in ordinary cholesterol. Likewise phytosterol, which had been purified similarly by means of a bromine derivative, failed of activation by ultra-violet irradiation.

Over-radiated cholesterol which had been recrystallized, could not be activated.