Attempts to separate the active constitutent of ragweed pollen.

As ragweed appears to be the chief cause of hay fever in this country it seemed desirable to attempt to separate the substance in the pollen which is responsible for the sensitization of hay-fever patients.

A number of the constituents have been characterized by Heyl, but this author did not attempt to test systematically the various fractions which he isolated. Recently Coca and assistants subjected ragweed extract to the action of trypsin. On dialysis most of the nitrogenous consituents diffused through the membrane while the residue retained its activity; therefore the authors conclude that the active substance is not a protein.

Having found that 3 per cent ammonia was a useful solvent for the preparation of horse dander and other proteins used in clinical work, we also employed it for the extraction of ragweed pollen. Ammonia possesses certain advantages. It is a weak alkali with little racemizing or hydrolyzing effect and the protein obtained by precipitation of the ammonia extract with acetone is readily freed from alkali by drying in vacuo over sulfuric acid.

As the thick hard capsule is said to form 65 per cent of the pollen (Heyl) it was thought that extraction would have to be preceded by thorough grinding, but it was found that ammonia penetrated the capsule and completely extracted the active substance.

The preparations were tested by the cutaneous reactions on patients sensitive to ragweed. The varying sensitiveness of patients had to be considered in the interpretation of reactions.

The following results were obtained with the ammonia extract: