The absorption spectrum of vitamin D

Abstract

The action of ultra-violet radiation on ergosterol was studied by comparing the absorption spectra and antirachitic activity of the products formed. Three substances (or groups of substances) are produced in succession, of which the 1st shows an absorption band roughly similar to that of ergosterol (maximum 280 [mu][mu]), but more than twice as intense. This absorption is accompanied by great antirachitic activity, and evidence is given showing that the substance concerned is probably vitamin D. The 2nd product, formed by further radiation of the 1st, shows a strong absorption band with maxima at 240 [mu][mu] and has no antirachitic activity. The. 3rd substance is formed by further radiation of the 2nd, and shows neither antirachitic activity nor marked absorption. A method of calculation is described by which the actual % of vitamin D in the purest preparations studied is estimated as over 50. Absorption curves are shown which are believed to be closely similar to those which would be shown by pure preparations of vitamin D and of the 2nd product of radiation.