Pyridoxine and Pyridoxine-5′-β-D-Glucoside Exert Different Effects on Tissue B-6 Vitamers but Similar Effects on β-Glucosidase Activity in Rats

Pyridoxine glucoside is a partially available form of vitamin B-6 present in plant-derived foods. In this set of three studies, rats were fed diets containing different concentrations of either pyridoxine or pyridoxine glucoside in the presence or absence of a fixed concentration of pyridoxine for 2 wk. The distribution of B-6 vitamers and β-glucosidase activity in tissues was examined to determine the metabolic effects of chronic consumption of pyridoxine glucoside. Rats fed pyridoxine glucoside either with or without pyridoxine exhibited a significant increase in the amount of hepatic pyridoxine 5′-phosphate (not detected in rats fed pyridoxine alone), whereas hepatic pyridoxal 5′-phosphate was decreased with increasing dietary pyridoxine glucoside. The activity of cytosolic β-glucosidases in small intestine and kidney was affected by the dietary concentration of both pyridoxine and pyridoxine glucoside. Enzymatic activity capable of hydrolyzing pyridoxine glucoside was found in mucosal and intraluminal fractions of small intestine and in the kidney. Other tissues examined, including liver, spleen and stomach, did not hydrolyze pyridoxine glucoside in detectable quantities. These findings indicate that microbial and mucosal enzymes can participate in the intestinal hydrolysis of pyridoxine glucoside and that the kidney may contribute to postabsorptive hydrolysis. These findings further support the observations that dietary pyridoxine glucoside influences vitamin B-6 metabolism.