ビタミンD_2散剤の安定性に関する研究(第6報) : ビタミンD_2の異性化におよぼすビタミン類および酸の影響

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Examination was made on the relationship between acid strength (pK_a) of solid surfaces and isomerization of vitamin D_2 (D_2). A mixtures of D_2 and other powdered vitamins was stored at 37° in vacuum (1 mmHg). It was found that D_2 was readily isomerized by vitamins such as ascorbic acid, folic acid, thiamine hydrochloride, or pyridoxine hydrochloride, as well as by talc or CaHPO_4,because each vitamin has a pK_a of 2.0 to 4.0 in the dry state. Nicotinamide and calcium pantothenate, both having a pK_a of 4.8 to 6.8,did not isomerize D_2. D_2 was isomerized also by citric acid or phosphoric acid in dry preparations. It is undesirable, threfore, to use any of the above acids as a synergist for an antioxidant to prevent the oxidation of D_2. The main isomerization products of D_2 were isocalciferol, 5,6-cis-isocalciferol, and isotachysterol.
社団法人日本薬学会の論文
1969-07-25