Extraction procedure and determination of the vitamin B12 content of some animal livers.

Abstract Employing a turbidimetric adaptation of the U.S.P. XIV microbiological assay, a number of procedures were studied for the extraction and stabilization of vitamin B 12 of liver tissue. Consistently high values were obtained by digesting homogenized liver tissue with crude papain at 60 ° for one hour followed by the addition of sodium metabisulfite (1 mg./ml.) and steaming for 5 min. The protective effect of metabisulfite on the vitamin B 12 activity during the heating of liver samples has been confirmed. The following average values for the apparent vitamin B 12 activity (in micrograms per gram) were obtained for the respective liver samples: cow 1.18; buffalo 1.30; sheep 1.33; goat 1.20; pig 0.59; rabbit 0.60; chicken 0.27; rat 0.052; mouse 0.75. These results and the corresponding values for the alkali-stable vitamin B 12 activity observed in the course of the investigation have been discussed in the light of those reported in the literature.