In acute toxicity test on mice, it was proved that the toxicity of pyridoxal-DL-homocysteine (I) is lower than that of pyridoxal phosphate (II) or pyridoxine hydrochloride (III). (I) showed the vitamin B_6 activity approximately equivalent to that of (II) or (III) for the growth of vitamin B_6-deficient rat and also for the convulsion caused by antivitamin B_6 agents. In detoxication and hypercholesteremic tests, (I) was more effective than either (II) or (III). (I) had also anti-anemic potency and additive effect on diuretic. In riboflavin and vitamin B_6 deficient rat, the rates of elevatinon of total vitamin B_6 and (II) levels in tissues after an administration of (I) were nearly the same with (II) or pyridoxal. The blood levels of vitamin B_6 in dog and rat after an oral administration of (I) was almost equal to that of (II), while the levels was sustained longer in the intracutaneous injection of (I) than that of (II). The microbiological activity for various lactic bacteria and Saccharomyces carlsbergensis, (I) was almost equivalent to pyridoxal.
