The Parent Substance of Vitamin D

Abstract

Purified stigmasterol and sitosterol irradiated with ultra-violet light failed to protect rats against rickets. Over-irradiation of cholesterol destroys vitamin D. Digitonin precipitates the provitamin from the non-saponifiable fraction of olive oil. When examined spectroscopically, the absorption of ergosterol in the ultra-violet region (280[mu][mu]) is found to be 2000 times that of ordinary cholesterol. The characteristic absorption bands of ergosterol disappear as the sterol is is irradiated to form vitamin D, and it is no longer precipitable by digitonin. Feeding tests show that as little as 1/10,000 mgm. prevent and cure rickets in rats. Irradiated ergosterol kept in an inactive oil for 11/2 yrs. was still active when fed at a level of 1/1000 mgm. It is concluded that the natural parent substance is ergosterol, or a highly unsaturated sterol of similar constitution, which is converted into vitamin D by irradiation.