Analysis of Free and Glycosylated Vitamin B6 in Wheat by High-Performance Liquid Chromatography' (1995)

Cereal Chem. 72(2):217-221 We developed an high-performance liquid chromatography (HPLC) extraction of wheat B6 using metaphosphoric acid followed by quantitamethod for analysis of vitamin B6 in wheat, based on modifications of tion of B6 in a single binary-gradient HPLC separation. Analysis of three existing reverse-phase ion-pairing procedures. The method is much simpler randomly selected wheat cultivars with this method revealed significant than multistep HPLC-based procedures required for exhaustive analysis variation in content of pyridoxine (2.2-3.3 nmol/g) and pyridoxine of all B6 forms in foods, including minor components, or methods based glucoside (1.8-9.4 nmol/g). The method should facilitate analysis of on microbiological analysis. The method is suitable for analysis of major different wheat cultivars for vitamin B6 content. B6 forms in wheat, including pyridoxine glucoside. The method entails Wheat is an important food source for both humans and animals in many cultures of the world (Bushuk 1986), and it is a significant source of vitamin B6, particularly in nonmeat diets (National Research Council 1989). More than 50% of vitamin B6 consumed by Americans comes from plant foods (Kant and Block 1990). Adequate intake of vitamin B6 is essential because of its key coenzymatic role in over 100 enzymes of protein, lipid, and carbohydrate metabolism (Leklem 1988). The recommended dietary intake for vitamin B6 is 2.0 mg/day and 1.6 mg/day for men and women, respectively (National Research Council 1989). Marginal vitamin B6 nutritional status is prevalent in the United States; data show that 71 and 90% of American males and females, respectively, consume less than the recommended daily allowance (RDA) for vitamin B6 (Kant and Block 1990). Selhub et al (1993) recently reported that about half of the elderly subjects in the Framingham study consumed less than the RDA of B6, and that such intake is associated with significantly elevated plasma homocysteine, which in turn significantly increases risk for development of cardiovascular disease. In an accompanying editorial, Stampfer and Willet (1993) conclude that vitamin supplementation (for folate and B6) may be appropriate for many elderly Americans. Using serum metabolic markers, Joosten et al (1993) concluded that vitamin deficiencies, including vitamin B6, may be more prevalent in the elderly than plasma markers for those vitamins suggest. Vitamin B6 includes a group of three 3-hydroxy-2-methylpyridine derivitives that exist in foods (and mammalian tissues) in phosphorylated and nonphosphorylated forms. These forms include pyridoxine (PN), pyridoxal (PL), and pyridoxamine (PM), as well as phosphorylated forms for PL and PM (PLP and PMP, respectively). These B6 vitamers all have high bioavailability, meaning they are well-absorbed and well-utilized in both humans and animals. An additional glycosylated adduct of PN, 5'-O-(f3-D-glucopyranosyl)pyridoxine, or pyridoxine glucoside (PNG), was first identified in rice bran (Yasumoto et al 1977) and occurs in many plant foods. PNG has potential nutritional significance due to its low bioavailability compared to nonglycosylated B6 vitamers (Gregory and Kirk 1981). Kabir et al (1983) found an inverse relationship between the PNG content of the diet and its bioavailability in humans. Reynolds (1988) found the percent PNG in foods was a strong predictor of bioavailability. Studies have shown that PNG bioavailability is low compared to PN in both rats