Biological Assay of Folic Acid Activity in Common Feedstuffs

VERY little information has been available on the distribution of folic acid (liver Lactobacillus casei factor, pteroylglutamic acid, vitamin Bc) in common feedstuffs and other materials. The reason for this lack of information may be attributed largely to various difficulties encountered in microbiological assay methods for this vitamin. Liver and yeast are known to be rich sources of folic acid. Other materials which have been tested for folic acid by microbiological methods include leafy vegetables such as spinach and lettuce, malt sprouts, soybeans, grass juice, ground corn, polished rice, rice bran, whey, bone marrow, and meat scraps (see review by Wieder, 1946). For most of these sources mentioned, very few quantitative figures have been given. One reason for the difficulty of assay of folic acid by microbiological procedures is that at least one conjugated form of this vitamin exists in naturally occurring materials (Binkley et al. 1944). As yet, no . . .