Utilization as Molecular Container of Layered Double Hydroxides for Vitamins

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For the development of biocompatible and health supporting materials, we have studied on the utilization of layered double hydroxide (LDH) as ‘Molecular container'. In this study, the intercalation of vitamin C (L-ascorbic acid) and vitamin A acid (retinoic acid) into tree kinds of LDH was investigated, as well as the stability of these guest vitamins in LDH and the release of vitamins from the resulting composites.First, Mg-Al,Mg-Fe and Zn-Al LDHs were adopteted as host hydroxide layers. It was found the vitamin C was intercalated only in Mg-Al and Mg-Fe LDHs by the reconstruction method and only in Mg-Al and Zn-Al LDHs by the coprecipitation method. The intercalation isotherms were obtained in each cases and all the data was well-treated by the Freundlich adsorption equation. Moreover, vitamin A acid was also intercalated in Mg-Al LDH.On the other hand, there is two types of vitamin C, i.e.,reduced type and oxidized type, and only the former demonstrates the reducing and physiological functions. After the white light irradiation treatment or heat treatment of the resulting vitamin/LDH composites, the amount of reduced type vitamin C in the composite was found to be about two times compared to that of the naked one in the same condition. Then, 82〜97% vitamin C was released from the composites by the anion exchange with carbonate ion. In addition, vitamin A acid was also stabilized in the interlayer of Mg-Al LDH and easily released by the same anion exchange.In conclusion, LDH can be used as ‘molecular container' for vitamins.