The activity for chicks of some vitamin B12-like compounds

Abstract
Ten analogues of vitamin B12 were tested for B12 activity in chick growth. The only naturally occurring analogue to show activity was the 5-hydroxybenziminazole derivative (vitamin B12III), which had 4-5% of the activity of vitamin B12. Four analogues containing benzim-inazole in the nucleotide also had vitamin B12 activity; they were the analogues with benziminazole (23%), monomethylbenziminazole (35-41%), dichlorobenziminazole and naphthiminazole (the last 2 almost as active as vitamin B12 itself). Pseudovitamin B12 and factor B in large doses by mouth, but not by injection, reduced the effect of vitamin B12 given simultaneously. In a single test factor D showed similar antagonism when inactive, but not antagonistic to vitamin B12.