ビタミンD2散剤の安定性に関する研究(第1報) : 賦形剤の表面酸性とビタミンD2の異性化の関係 その1
1969 年 89 巻 7 号 p. 909-913
詳細
1969 年 89 巻 7 号 p. 909-913
During studies on the stability of vitamin D2 (D2) with various excipients, it was found that D2 is readily isomerized in powders prepared with CaHPO4 or talc, yielding isocalciferol and isotachysterol, and that this isomerization is catalyzed by surface acid on the excipients. In this paper, the isomerization reaction was examined in n-hexane solutions of D2 in which natural aluminum silicate (pKa -8.2 to -5.6), CaHPO4 (pKa 0.8 to 1.5) or talc (pKa⪈1.5) was suspended. The end products were isotachysterol and a small amount of isocalciferol, and the initial isomerization rates of D2 were found to be dependent on the acid strength (pKa) and acidity of the solid surfaces. The rates were independent of the initial concentration of D2, if excess D2 remained in the liquid phase. The apparent activation energy in this isomerization reaction was about 25 kcal mole-1. When n-butylamine was chemisorbed on solid surfaces, the rates decreased proportionally with increasing amine content.
