PYRIDOXINE-5'-BETA-D-GLUCOSIDE AFFECTS THE METABOLIC UTILIZATION OF PYRIDOXINE IN RATS

A major form of vitamin B-6 in plant-derived foods is pyridoxine-5'-beta-D-glucoside. Previous studies have shown that pyridoxine-5'-beta-D-glucoside is poorly available as a source of vitamin B-6 in rats and is partially utilized in humans. This research was conducted to determine whether unlabeled pyridoxine-5'-beta-D-glucoside affects the metabolic utilization of simultaneously administered isotopically labeled pyridoxine in rats. Three groups of rats (n = 6) were administered a single oral dose of 0, 36 or 72 nmol of unlabeled pyridoxine-5'-beta-D-glucoside along with 166.5 MBq (240 nmol) of [C-14]pyridoxine. Twenty-four hours after administration of the dose the rats were killed, and the isotopic distribution of vitamin B-6 metabolites in liver and urine was determined. Urinary C-14 and hepatic C-14-labeled pyridoxine phosphate and pyridoxal phosphate were directly related to pyridoxine-5'-beta-D-glucoside dose. Hepatic C-14, C-14-labeled pyridoxal, pyridoxine and pyridoxamine, and the concentration of urinary [C-14]4-pyridoxic acid, relative to total urinary C-14, were inversely proportional to the dose of pyridoxine-5'-beta-D-glucoside. These results provide evidence that pyridoxine-5'-beta-D-glucoside quantitatively alters the metabolism and in vivo retention of [C-14]pyridoxine and that pyridoxine-5'-beta-D-glucoside may retard the utilization of nonglycosylated forms of vitamin B-6. J. Nutr. 122: 1029-1035, 1992.