The Estimation of Bile Acids in Bile

In a recent paper Foster and Hoop& (1) have described a rapid method for the estimation of bile acids in dog bile. The method depends on the fact that the two bile acids usually found in dog bile, viz. taurocholic and taurocholeic, on hydrolysis with alkali give taurine, which yields its nitrogen quantitatively in 4 minutes when shaken with HN02. Taurocholic and taurocholeic acids do not react with HNOz before hydrolysis. The proteins in bile are precipitated by hot alcohol which at the same time holds the bile salts in solution. A portion of the filtrate is evaporated to dryness and then hydrolyzed with 8 per cent NaOH for 6 hours. The taurine thus set free can be estimated from its yield of amino nitrogen. Since bile normally contains a small amount of free amino nitrogen, an estimation to allow for this is carried out on a separate portion of evaporated filtrate. Other nitrogenous constituents present in bile do not yield amino nitrogen with the exception of urea. But as the amount of urea present in bile-32 mg. per 100 cc. (2)-is small and since only about 3 per cent of its nitrogen is liberated in 3 minutes, this factor can be neglected. While this method is applicable to bile acids which on hydrolysis yield only taurine it does not differentiate between these acids and those having glycocoll in the molecule. Since bile from most animals, especially man, contains acids of both the glycocoll and the taurine series, we have concerned ourselves with the problem of devising a method which will differentiate between the two series of bile acids. Strecker (3) found that hydrolysis of glycocho$c acid by means of alkali gave cholic acid and glycocoll and we have confirmed