A Synthetic Oestrus-Exciting Compound
Cook, JW., et al / Nature 14jan33

In conformity with the hypothesis, for which there is at present no experimental basis, that the ovarian hormones are formed by degradation of sterols, and in the light of recent developments in the chemistry of the sterols, ketohydroxy-oestrin is possibly represented by formula (i).

This accords with all the facts supplied by the work of Butenandt¹, Marrian², and others, and we decided that the arguments in favour of this formula were sufficient to justify attempts to synthesise compounds of this nature. By analogy with other physiologically active compounds, it seems likely that a whole group of substances of related chemical constitution will be found to have oestrus-exciting properties, and the synthetic production of such substances would probably be of considerable clinical value.

We have found that 1-keto-1 : 2 : 3: 4-tetrahydrophenanthrene (ii), which we propose to utilise as a starting point in the synthesis of a substance of formula (i), has itself very definite oestrogenic action, although the dose required is very large in comparison with oestrin. The oestrus-producing activity of the substance was examined by the Allen and Doisy procedure. The technique followed was that described by Allan, Dickens and Dodds³. The material was dissolved first in olive oil, and later in sesame oil. It was found that the substances were not readily soluble in olive oil, with the result that large volumes had to be administered subcutaneously to the ovariectomized animals. This proved to be unsatisfactory owing to leakage from the site of injection and intolerance to the oil, but with sesame oil the volume could be kept down to 2 c.c., and these adverse effects avoided. 25 mgm. of the substance in olive oil administered to ten ovariectomized rats produced -no sign of oestrus, the animals remaining in a state of di-oestrus throughout the experiment. A batch of twenty animals injected with 50 mgm. dissolved in olive oil showed seven full oestrus responses, with three animals just short of the definition (a few leucocytes). In a series of twenty animals injected with 100 mgm. dissolved in sesame oil, a very much better response was obtained, all twenty animals going into oestrus. The oestrus in each case was complete.

In the case of the 50 mgm. dosage, oestrus appeared after 54 hours and terminated 150 hours after injection. In the case of the 100 mgm. in sesame oil, oestrus appeared after 52 hours. At the present moment, it is impossible to state the activity of the material in terms of oestrin since the relatively difficult solubility of the material together with the consequent difficulties of administration and absorption make a comparison impossible. Some form of `cross-over' method must therefore be evolved. There can be no doubt that a repetition of the standardisation experiments with 50 mgm. dissolved in a small volume of sesame oil would indicate much greater potency than a similar experiment conducted with olive oil as the vehicle.

The observations show that 1-keto-1 :2:3:4totrahydrophonanthrene is capable when injected into castrated animals of inducing oestrus of an exactly similar typo to that obtained by the injection of oestrin. This result is of importance, for 1-keto-1 : 2 : 3 : 4totrahydrophonanthrone is the first compound of known chemical constitution found to have definite oestrus-exciting activity and furthermore, its molecular structure has many points of resemblance to the structure suggested for ketohydroxy-oestrin. Thorn is thus provided the first stop in the task of defining the molecular conditions necessary for this typo of physiological activity, and there arc grounds for hoping that substances of 11, much higher order of activity will be found before very long.

The observation⁴ that oestrogenic properties of a low order are possessed by suitable extracts of such a variety of materials as peat, brown coal, lignite, coal tar and petroleum is of interest, but in view of the fact that many such materials are known to contain carcinogenic constituents, the clinical use of such extracts without very stringent refinement is scarcely to be entertained.

We have also examined 4-koto-1 : 2 : 3: 4-tetrahydrophenanthrene (iii) and 3-hydroxyphenanthrene ; these gave no oestrus response when injected in doses of 50 mgm.

We are indebted to Dr. H. Allan for kindly checking over the animal experiments.

J. W. COOK.
E. C. DODDS.
C.L HEWETT.

Research Institute,
     The Cancer Hospital (Free),
          London, S.W.3.
Courtauld Institute of Biochemistry,
     Middlesex Hospital,
          London, W.1.

[References]

¹  Z. physiol. Chem., 208, 129 ; 1932.
²  J. Soc. Chum. Ind., 51, 277 T ; 1932
³  J. Physiol., 68, 348 : ; 1930.
⁴  Shering-Kahlbaum : Fr. Pat., 710,857.