Abstract
3'-or 5'-Substituted pyridoxal (PAL) derivatives were parenterally administered into rabbits and rats (10mg/kg) and the resultant B_6 levels in the blood and liver were determined. Among seven compounds tested, PAL-5'-n-butyrate, PAL 5'-isobutyrate and PAL 5'-benzoate gave higher peak levels with larger biological half lives of blood total PAL. On the intraveneous administration of these three compounds, the elimination process were specifically followed by a 2-phased first order kinetics though the reason of which was unexplained. Less lipophilic 5'-substitutes, PAL 5'-acetate, PAL 3', 4'-diacetate, PAL 5'-succinate and PAL 3'-n-butyrate gave similar B_6 levels to that of PAL administration. PAL 5'-acylates were confirmed to be hydrolyzed in the blood, mainly by a kind of plasma esterase. The esterase activity was somewhat different with animal species and the kind of substitutes. From these findings effects of 5'-acylation on the biopharmaceutical behavior of PAL are discussed.
