“Further observations upon the phosphorized fats in extracts of the kidney”

Last winter, at a meeting of this society (Proceedings, Vol. I, page 39), the author reported observations showing that extracts from dried kidneys, obtained with the Rosenfeld alcohol-chloroform method, contained from a third to two-thirds of their weights of lecithins. Rubow, 2 of Copenhagen, reported similar results of more extended studies, printed in Danish some months earlier.

During the last few months the author has learned that it is not necessary to boil with absolute alcohol and extract with chloroform in order to obtain the large quantities of extract yielded by the Rosenfeld method. Repeated extraction of the fresh, undried organ, with 85% alcohol at 45∗deg; C., will accomplish practically the same result. When making these extracts, it was found that upon cooling, the alcoholic solutions yielded a precipitate from which a substance resembling the protagon of Liebreich could be obtained. It is to this substance that the author directs attention in this report. The yield is from about o. 14% to 0.20% of the fresh organ, or from about 0.6% to 1.0% of the dried kidney.

“In order to obtain sufficient material for analysis, the author employed the method used by Cramer” in preparing protagon from the brain. The method employed was, in brief, as follows : The minced kidney, freed from obvious fat, was treated twice with 5% sodium sulfate solution at 85 ° C. to 90 ° C.; the filtrates were discarded and the coagulum extracted, first with 95% alcohol and then repeatedly with 85% alcohol, at the boiling points, and the extracts filtered from the coagulum on a hot-water funnel. The filtrates were cooled to from 0 ° C. to − 5 ° C., the precipitate was filtered out and purified by boiling with absolute alcohol, diluting the filtrate with water to make 85 % alcohol, chilling, filtering, treating the precipitate repeatedly with cold ether to remove cholesterin, dissolving in hot chloroform, reprecipitating by chilling, filtering and expressing all possible traces of chloroform.