DEVELOPMENTS IN THE CHEMISTRY OF VITAMINS
143
Calciferol and Suprasterols I and II, which formed stages in a continuous trans-
formation, and which could be isolated by the careful adjustment of experimental
conditions and studies. With the collection of this material the chemistry of
vitamin D in this sense of structural organic chemistry had just begun to unfold.
(The methods which had been particularly serviceable in the elucidation of the
structures of these photo-isomerides, such as oxonolysis, catalytic hydrogenation,
selenium dehydrogenation and addition with maleic anhydride (Diels-Alder reac-
tion) were discussed in detail and how the constitution of ' Calciferol ' had been
established with tolerable certainty by these methods was explained with the aid
of slides). In the light of these findings, the view which prevailed at the beginning,
that the active anti-rachitic principle in fish-liver oils was nothing else than acti-
vated ergosterol, and that all foods and animal tissues which were capable of
being rendered anti-rachitic by irradiation contained only ergosterol, was shown
to be no longer tenable the accumulated evidence indicating the existence of
many other pro-vitamins although the exact nature of these remained unknown.
That calciferol or as it might be called the synthetic vitamin D, was different from
the natural vitamin D of cod-liver oil, had been demonstrated satisfactorily
by several workers recently and it was now considered probable that any sterol
which contained a conjugated system of ethylenic linkages in positions 5, 6, 7
and 8 should be capable of being transformed into an anti-rachitic factor by
irradiation with ultra-violet light, a view which received striking support lately
from an observation made with a synthetic derivative of cholesterol (7 dehydro¬
cholesterol) which could be converted into a highly active anti-rachitic product.
THE NEW ANTI-STERILITY VITAMIN
We shall now consider vitamin E (Evans) which is prepared from the oil
extracted from wheat embryos by the usual process of removal of saponificable
matter, chromatographic absorption, distillation in high vacuum, etc. This vita-
min has been called anti-sterility vitamin. The chemical examination of the
most active fraction (a pale yellow oil) obtained in this way showed it to have an
unsaturated structure and to be of the nature of a cyclic ketone capable of exhi-
biting ketonal changes, with a molecular weight of about 450 and having two
oxygen atoms one of which could be acetylated. It was fairly stable and could be
hydrogenated in the presence of palladium without losing its activity but bromina¬
tion, acetylation and oxidation destroyed its potency. Although the successful
treatment of sterility in cows and of habitual abortion in women by means of this
concentrate had been reported recently, the actual function of vitamin E in the
body was not definitely known, and the important questions as to whether this
vitamin was related in any way to the numerous hormones which regulated the
normal reproductive cycle or if the deficiency of this vitamin was associated in
any way with disturbances in the functions of the pituitary glands or of the corpus
luteum had not yet been adequately examined.
K