Preparation and Antibacterial Characteristics of Hinokitiol-intercalated Layered Double Hydroxides
Toshihide YAMAGISHI* and Eiiti NARITA†
Department of Chemical and Biological Engineering, Hachinohe National College of Technology; Tamonoki, Hachinohe-shi 039-1192 Japan
† Department of Chemical Engineering, Faculty of Engineering, Iwate University; 4-5-5 Ueda, Morioka-shi 020-8551 Japan
Hinokitiol (4-isopropyltropolone)-intercalated layered double hydroxide (LDH) has been tried to synthesize by the calcinations-rehydration reaction (reconstruction method) using the M2+-Al3+-CO32− LDHs (M2+=Mg2+, Cu2+, Ni2+ and Zn2+), and the properties and antibacterial activity of the resulting LDH have been investigated. The calcined products obtained from Mg2+-Al3+ and Zn2+-Al3+ LDHs could reconstruct to form the hinokitiol-intercalated LDH, in which the amount of hinokitiol intercalated was increased with increasing the relative quantity of the hinokitiol solution in spite of lower solubility of hinokitiol. From the X-ray diffraction analysis, hinokitiol anion in the interlayer of the LDH was arranged as parallel to the hydroxide layer in the case of smaller intercalated amount, while it was incorporated overlapping in the intercalated with increasing the intercalated amount. It was also found that hinokitiol in the interlayer was released slowly from the LDH particles by the ion-exchange and its thermal decomposition temperature became about 200 °C higher compared to hinokitiol itself, which means an increase of heat-stability. From the result of the antibacterial activity tests using Eschericia coli, the minimum inhibitory concentration was found at 800 mg dm−3 of the total hinokitiol concentration both in the hinokitiol-intercalated Mg2+-Al3+ and Zn2+-Al3+ LDHs.
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