理论探究咖啡因N_3和N_7位水解去甲基代谢机理

Theoretical Study on the Hydrolysis Demethylation Metabolic Mechanisms of Caffeine at N_3 and N_7 Sites

采用BH&HLYP/6-311++g(d,p)方法研究了咖啡因N3和N7位水解代谢机理.每个N位的水解代谢机理考察了两种可能的反应路径:分步的路径A和协同的路径B.计算结果表明:对于N3或N7位水解代谢,路径A均优于路径B;N3位水解代谢的路径A所需的活化自由能(358.8 k J·mol-1)低于N7位(363.1 k J·mol-1),因而代谢产物副黄嘌呤优于茶碱.

The hydrolysis metabolic mechanisms of caffeine at N3 and N7 sites were clarified in this paper under the BH＆HLYP/6-311 ＋ ＋ g（d,p） theory. Two possible reaction pathways were identified for each N-site hydrolysis metabolic mechanism： the stepwise path A and the concert path B. The calculation results showed that path A was more favorable than paths B for both the N3- and the N7-sites hydrolysis metabolic mechanism. The activation free energy of path A involved in N3-site hydrolysis metabolic mechanism （358.8 kJ·mol^-1） was lower than that of N3-site （363.1 kJ·mol^-1 ） and the metabolite paraxanthine therefore was more favorable than theophylline.