How To Keep Your Stash Strong For 10 Years
Experiment on the Cause of the Loss of Activity of Indian Hemp, National Druggist, May 1909
Eleven years ago, as part of an investigation on the pharmacological action of cannabis indica, I made some experiments to determine the cause of the loss of activity of this substance. My attention was first drawn to the matter by noting that cannabinol, isolated from charas by Wood, Spivey, and Easterfield, began to darken at the surface when left in an open test tube. This at once suggested that oxidation was occurring and, on thinking over the matter, it seemed not improbable that oxidation might account for the loss of activity of preparations of Indian hemp on keeping.
This explanation had been suggested by Leib Lapin four years previously, but his experiments on the point were not convincing. He had isolated an active, semi-solid, cherry-red substance from Indian hemp which possessed reducing properties, and which, on being rubbed up with chocolate and left for a week, lost a considerable part of its physiological activity. This he explained as being due to oxidation of the active substance owing to its finely divided state.
My own experiments were made by passing oxygen through cannabinol. Two test tubes containing a specimen of the same cannabinol were placed in a bath of sulphuric acid at 150°-160° C, in order to keep the cannabinol quite fluid, and through one specimen a gentle stream of oxygen and through the other a similar stream of carbon dioxide was passed. The cannabinol subjected to the action of oxygen rapidly darkened, and its consistence increased, and after the oxygen had bubbled through it for six hours its physiological action was found to be decidedly less than at first. The oxygen and carbon dioxide were passed through the specimens for thirteen hours more, the temperature of the bath being raised towards the end of the experiment to 185° C, in order to keep the oxygenated cannabinol fluid. On cooling, this cannabinol set to a hard, brittle mass, resembling pitch in appearance. It was found to produce no physiological effects unless dissolved and administered in oil, when a slight reaction was observed. An analysis made by Dr. Easterfield showed that the cannabinol had undergone oxidation.
The cannabinol subjected to the action of carbon dioxide was scarcely changed: there was no evident alteration in consistence, and only a very slight darkening, due in all probability to the presence of a small amount of air in the carbon dioxide, had occurred. Its physiological action was practically the same as before the experiment.
Owing to these results. I decided to seal hermetically a specimen of cannabinol in a test tube. This was done on December 28, 1898. The tube was opened for the first time on February 15, of this year, having lain for ten years and fifty days. For most of this time it has been exposed to the light of a well-lit room with a north aspect. It has undergone no apparent physical change, and has lost none of its physiological activity.
For comparison, a large mass (about 8 kilos) of the original charas from which the cannabinol was prepared was kept exposed in a dark store, and from the central part an alcoholic extract has been made and fractionally distilled. The fraction coming over at 260°-295° C. under 15 Mm. Hg. pressure, which should have been mainly active canabinol, was found to be almost inert. It was at least ten times less active than the cannabinol which had been sealed up.
There is good reason to believe that preparations of cannabis indica relatively quickly deteriorate. My experiments suggest that if these — and the remark applies more particularly to the extract and similar preparations — were put up in hermetically sealed vessels, and the vessels resealed each time after use, greater uniformity in the action of a particular preparation would be obtained.—Pharm. Jour.
*By C. R. Marshall, M. A., M. D., Professor of Materia Medica and Therapeutics in, the University of St. Andrews.