The Effect of Gamma Radiation on a Number of Water Soluble Vitamins.

Solutions of thiamin hydrochloride, riboflavin, niacinamide, biotin, pteroyiglutamic acid, and N/sub 5/-formyltetrahydropteroylglutamic acid were irradiated with gamma rays from a Co/sup 60/ source. Residual activity as well as the formation of biologically active breakdown products was studied using microbiological test systems. No microbial growth factors other than the vitamins themselves were detected in irradiated solutions of thiamin, riboflavin and niacinamide. Biotin-L-suifoxide was formed on irradiation of biotin and pteroic acid on irradiation of pteroylglutamic acid. A great number of biologically active breakdown fragments were observed in irradiated solutions of N/sub 5/-formyltetrahydropteroylglutamic acid, amongst them pteroylglutamic acid, N/sub 10/-formylpteroic acid, pteroic acid, and N/sub 10/-formylpteroylglutamic acid as well as three chemically unidentified growth factors. It was noted that the degree of destruction as determined spectrophotometrically appeared to be considerably lower than found on microbiological estimation. (auth)