VITAMINS

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Possible roles of vitamin D-transport proteins in the expression of biological activities of vitamin D were investigated. In vitro binding studies of vitamin D and its derivatives on DBP (vitamin D-binding protein) and VDR (vitamin D receptor) have revealed that there was a significant relationship between chemical structures and binding affinities to DBP and VDR, and suggested that it could be possible to regulate the expression of biological activities of vitamin D by changing structurally. To clarify the possibility, OCT (oxacalcitriol) and Ed-71 (2β-(3-hydroxypropoxy)-1 α, 25-dihydroxyvitamin D_3), which were given side-chain modification or A-ring substitution on the structure of 1,25(OH)_2D_3 respectively, were synthesized and their biological activities were examined. The results clearly demonstrated that the structural modification could strength or separate the biological activities of 1.25(OH)_2D_3 by changing binding property to DBP. To evaluate the nutritional significance of vitamin D in human breast and cow's milk, we assayed the levels of vitamin D and its metabolites in both milk. Neither breast mild nor cow's milk contained vitamin D-sulfate. The total antirachitic activities in breast and cow's milk calculated by Reeve's conversion factors were 130 1U/liter equally. Furthermore, we have demonstrated that the concentrations of 1,25(OH)_2D_3 in skin and bone marrow were very similar to that in plasma.

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Oxygen-derived free radicals have been reported to be closely involved in the development of tissue injury induced by ischemia-reperfusion in several organs, such as heart, brain, lung, liver, stomach, small intestine, kidney and so on. Ischemia itself causes tissue damage, but further injuries can occur when oxygen is reintroduced to the tissue. Furthermore, lipid peroxidation mediated by free radicals is believed to be one of the important causes of biological membrane destruction and cell damage. It has been reported that Vitamin E exists in the cell membrane of various tissues and functions as a lipid-soluble antioxidant by scavenging oxygen-derived free radicals and terminating free radical chain reaction. In experimental ischemia-reperfusion injury model, vitamin E in the tissue was significantly decreased after ischemia-reperfusion. On the other hand, in Vitamin E-deficient animals, ischemia-reperfusion injury was more severe than in Vitamin E-nondeficient animals. These results indicate that Vitamin E is consumed in the process of lipid peroxidation induced by free radicals in ischemia-reperfusion to prevent the development of tissue damage.

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In this study, using high performance capillary electrophoresis (HPCE) with an improved fluorescent detector, we have devoloped the conditions for separation of vitamin B_6 group and proposed a new system for analysis of B_6 group. This method has advantage in mass sensitivity (ca 1 pg- 1 ng) and shortened time of analysis (within 20 min). though B_6 group in fluid including proteins have been difficult to determine, it showed high resolution and reproducibility for B_6 analysis except for PLP in the presence of standard serum proteins, using handmade microdialysis probe.

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Homogenization using a blender is usually done in sample preparation. But, tocopherols in some of fresh foods were found to be decomposed by the homogenization. The addition of pyrogallol to the foods at the level of 10% could effectively prevent the decomposition of tocopherols. The effect of pyrogallol was examined for 110 foods, and it was found to be remarkable in japanese batterbur, cabbage, eggplant, potato, green gram sprouts, edible burdock, bamboo shoots, japanese plum, pond smelt and sardine. Recoveries of α-tocopherol and α-tocopherylquinon from eggplant were 97.2% and 87.9%, respectively. Tocopherols in the homogenized foods were decreased even at -18℃, while those in the foods with pyrogallol were stable. It was found that oxidized intermediate products to be present in the homogenized foods regenerated to α-tocopherol when pyrogallol was added and incubated at 37℃ for 30~60 min.

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