ドコサン酸-ニコチン酸アミド複合体からのニコチン酸アミドの遊離に対する熱力学的検討

抄録

Nicotinamide (NAA) forms a crystalline complex with docosanoic acid (C22), C22-NAA. The molar ratio of C22 to NAA is 1 : 1. The release rate of NAA from C22-NAA was measured above 47°C at pH 1.2 and pH 6.8, and the thermodynamic quantities for the release of NAA from C22-NAA were estimated. The value of activation energy (E^≐̸) at pH 6.8 was about three times larger than that at pH 1.2. The effect of temperature on the release rate of NAA from C22-NAA at pH 6.8 was larger than that at pH 1.2. It has been reported that the values of activation enthalpy (ΔH^≐̸) and activation entropy (ΔS^≐̸) at pH 1.2 for the release of NAA from fatty acid (FA)-NAA complex whose carbon number of constituent FA is 14-18 were positive and negative, respectively. On the contrary, the values of ΔH^≐̸ and ΔS^≐̸ for the release of NAA from C22-NAA at pH 1.2 and pH 6.8 were positive. Furthermore, the values of ΔH^≐̸ and ΔS^≐̸ at pH 6.8 were larger than those at pH 1.2. The value of activation Gibbs energy (ΔG^≐̸) was positive. It was found that the release of NAA from C22-NAA was enthalpically controlled reaction.