Contents of All Forms of Vitamin B₆, Pyridoxine-β-Glucoside and 4-Pyridoxic Acid in Mature Milk of Japanese Women According to 4-Pyridoxolactone-Conversion High Performance Liquid Chromatography

Abstract

The contents of six vitamin B₆ forms, pyridoxine-β-glucoside, and 4-pyridoxic acid in mature milk of 20 Japanese lactating women consuming ordinary Japanese foods were determined by a 4-pyridoxolactone-conversion HPLC method. These compounds were determined with the average recovery rate of 83.9% or more. The average total content of vitamin B₆ forms was 1.01±0.32 (μmol/L). Pyridoxal and pyridoxal 5′-phosphate were found in all of the samples, and their average contents were 0.71±0.28 (μmol/L) and 0.16±0.07 (μmol/L), respectively. Pyridoxamine, pyridoxine, pyridoxamine 5'-phosphate, pyridoxine 5'-phosphate, and pyridoxine-β-glucoside were found in 15, 14, 13, 9, and 7 samples, respectively. The presence of pyridoxine 5'-phosphate was for the first time found in human milk. A method for the determination of 4-pyridoxic acid, which is the excretion form of vitamin B₆, was modified to quantitate it by isocratic HPLC. 4-Pyridoxic acid was found in all samples, and its average content was 0.094±0.040 (μmol/L), which was only 12% of its content in cow (Holstein) milk. The total content of vitamin B₆ forms, and predominant presence of pyridoxal among other vitamin B₆ forms in the Japanese women's milk samples shared similar characteristics with American women’s milk samples.