Abstract
Aqueous solutions of vitamin B_6 relating compounds and 4-pyridoxic acid were exposed to sunlight to compare the stability at pH 3.0,7.0 and 9.0. Pyridoxine and pyridoxamine were relatively stable in an acidic medium, while decomposition of pyridoxal occurred independently on pH value. The fact suggests that oxygen participates in the photolysis of pyridoxal. Presence of Cu ion was found to have no effect on the stability of these substances. Borate complex of pyridoxine was stable in the sunlight irradiation as well as in heating or autoclaving. Acetic acid and a reddish brown substance were separated as the decomposition products from an irradiated solution of pyridoxine. It was found that the latter substance is precipitated by the addition of acetone or phosphotungstic acid, does not contain nitrogen and reduces Fehling's solution.
