Bioavailability of Vitamins B_1 and B_6 in Foods.

1. 食品中维生素B_6成分的同时定量方法：植物性食品中维生素B_6的主要形式是5'- o - （β - d -葡萄糖吡哆醇）吡哆醇（PNG），动物不能完全获得。建立了一种简便高效的液相色谱法，采用等容溶剂体系，单柱同时定量测定多种植物性食品中PNG和所有B_6维生素。该方法可在40分钟内得到精确的结果。用该方法测定的几种食品中维生素B_6成分的含量与文献报道的结果吻合较好。在食品加工和烹饪过程中维生素B_6活性的损失：在吡哆醇-抗坏血酸(AsA) -Cu^<2+>混合物和罐装果汁中，AsA的自氧化使维生素B_6含量降低了15-20%。蔬菜汁中维生素B_6的分解似乎随着添加AsA的量而变化。因此，抗坏血酸自氧化过程中产生的羟基自由基对维生素B_6的羟基化作用被推断为在食品加工和烹饪过程中导致植物性食品中维生素B_6损失10-20%的原因。植物性食品中的维生素B_1缀合物：植物性食品中的维生素B_1除了大豆、绿色大豆和紫菜（米糠、芥菜粉、小麦粉、小麦胚芽、纳豆和芝麻）外，以硫胺素及其磷酸酯的形式存在。所有食物样本均未检出硫胺素糖苷。在全大豆和脱脂大豆中发现了一种不明维生素B_1缀合物。该化合物的分离方法和化学结构尚无定论。

1. Method for Simultaneous Quantification of Vitamin B_6 Components in Foods : The primary form of vitamin B_6 in plant foods is 5'-O- (beta-D-glucopyranosyl) pyridoxine (PNG) that is incompletely available to animals. A simple high-performance liquid chromatographic method has been developed for the simultaneous quantification of PNG and all B_6 vitamins in various plant foods, using a single column with an isocratic solvent system. This method offered precise results within 40 min. The contents of vitamin B_6 components in several foods, which were obtained by this method, were in good agreement with those reported in the literature.2. Loss of Vitamin B_6 Activity During Food Processing and Cooking : In pyridoxine ascorbic acid (AsA) -Cu^<2+> mixtures and canned juice, the autooxidation of AsA reduced the vitamin B_6 content by 15-20%. Decomposition of Vitamin B_6 in vegetable juices seemed to vary according to the amount of AsA added to the juices. Hence, hydroxylation of vitamin B_6 by hydroxyl radical generated during the autooxidation of ascorbic acid was inferred to cause the 10-20% loss of vitamin B_6 in plant foods during food processing and cooking.3. Vitamin B_1 Conjugate in Plant Foods : Vitamin B_1 in plant foods except for soybeans, green soybeans and purple laver (rice bran, mustard powder, wheat flour, wheat germ, natto and sesame seeds) exsists as thiamin and its phosphate esters. Thiamin glycoside was not detected in all food samples tested. An unidentified vitamin B_1 conjugate was found in whole soybeans and defatted soybeans. The isolation method and chemical structure of the compound remains unsettled.