Vitamin D is absorbed from the intestine as mixed micelles consisting of bile salt, fatty acid, and monoglyceride, and is transferred to the lymphatic system. In blood, vitamin D and its major circulating metabolite, 25-hydroxycholecalciferol, are transported in the bound form with their respective specific binding proteins, which are isolated from the α_1-globulin fraction of human plasma. 1,25-dihydroxycholecalciferol (1,25-DHCC) is a major metabolite in target tissues, such as intestinal mucosa and bone, suggesting that it must be the final active form of vitamin D in both tissues. The cytoplasm of intestinal mucosa contains the 1,25-DHCC binding factor required for the transfer of 1,25-DHCC into the nuclei where most of 1,25-DHCC is located. The primary function of vitamin D is to enhance serum Ca level. Ca binding protein, Ca-ATPase, and alkaline phosphatase are known to facilitate Ca absorption at the brush border of the intestine. Vitamin D affects their activities. The relationship of these factors and the lipid composition of microvillar membrane is also discussed.
The authors presented papers on a physicochemical determination of vitamin D in fish and fish products in 1964. This paper reviews the recent developments of the methods to determine vitamin D in natural products. Since about 1960,there have been put some important improvements on the treatment of samples and the application of thin layer and gas liquid chromatography, gel filtration, mass spectrography etc. However, many of difficulties existing in the method of that time were not yet solved, especially in the case of vitamin D determination of natural products such as meats, dairy products, animal tissues or excrements. Further improvements are needed especially in the separation of vitamin D from large amounts of impurities such as sterols or vitamin A, and simplification of complicated procedures adopted in various methods of determinations.
Sarcoplasmic proteins including their soluble enzymes were interacted with B_1・HC1 and various kinds of thiamine derivatives, such as O-benzoylthiamine disulfide (BTDS), O-isobutylthiamine disulfide (IBuTDS), thiamine disulfide (TDS), and thiamine pyrophosphate (TPP) at 37℃ for 1 hour. After dialysis of reaction mixtures, protein-bound complexes were isolated by means of the starch gel electrophoresis, and combined thiamine was determined by the analysis of free thiamine after the treatment using Takadiastase or sodium thiosulfate. Results indicated that BTDS was reacted with albumin, while IBuTDS was especially reacted with lactate dehydrogenase protein in rat muscle. In the case of rabbit muscle, TDS and IBuTDS were shown to have an unknown pattern of combined thiamine in the cathode side on the starch gel electrophoresis. TPP showed many patterns seemed to be probably with peptides in the reaction with the rat and rabbit muscle.
An agar-plate diffusion method for the microbioassay of inositol in natural products using both Kloeckera apiculata and Saccharomyces carlsbergensis as test organisms was attempted. In case of K. apiculata assay, the inositol requirement of the organism was strictly exacting than that of S. carlsbergensis, though it was susceptible to temperature on growth. The growth zone on the assay plate of K. apiculata was more clear, sharply-defined and reproducible than that of S. carlsbergensis and a linear response to pure inositol solution containing 10 to 400μg per ml was demonstrated with the probable errors of 10% on statistical analysis. The inositol contents in several natural products obtained by cup-plate method were nearly equal to those obtained with turbidimetric one and the recovery experiments were satisfactorily successful. This method is simple, accurate and available for the routine assay of inositol in biological materials.
In the previous studies of this series, it was investigated the influence of water content on the change of vitamin A acetate and its changed products in aqueous ethanolic solution. This report describes the results of a similar study on the stability of vitamin A alcohol, an intermediate product of vitamin A acetate in aqueous ethanolic solution. Remaining rate of commercial vitamin A alcohol (contain antioxidants) and purified vitamin A alcohol (antioxidant free) were determined by UV spectrophotometric method and f-values were compared respectively. The amount of changed products of purified vitamin A alcohol were examined by alumina column chromatography and thin layer chromatography. The stability of vitamin A alcohol in 60〜100% ethanolic solutions at 35°, 50°and 100℃ decreased gradually as water increased. Five substances were recognized as changed products of vitamin A alcohol. (a) Anhydro vitamin A (R_F 0.67), (b) vitamin A ethyl ether (R_F 0.55), (c) vitamin A aldehyde (R_F 0.32), (d) unknown (R_F 0.05), (e) vitamin A acid (R_F 0.03). Especially physical property of vitamin A ethyl ether was examined by UV, IR, NMR and mass spectrometry. Although anhydro vitamin A were recognized as the changed products of purified vitamin A alcohol, retro vitamin A and its changed products were not recognized.