Meconoquintupline is a new alkaloid, the molecular structure of which has been determined, and may be extracted from Meconopis quintuplinervia Regel, a traditional Tibetan medicine. In this work, a full optimal calculation on the molecular geometry and electronic structure of meconoquintupline has been performed using ab initio and density functional theory (DFT) methods at HF/6-31G* and B3LYP/6-31G* level, respectively. The solvent effects of meconoquintupline have also been investigated based on Onsager self-consistent reaction field (SCRF) model in chloroform, acetone, DMSO and water. On the basis of the vibration analysis and statistical thermodynamic theory, the IR spectrum and thermodynamic parameters (enthalpy, entropy and heat capacity) for the titled compound from 298 to 1500 K have been obtained according to the B3LYP/6-31G* optimized geometry in gas phase. At the same time, the relationship between molecular structure and medicine efficacy for meconoquintupline has also been analyzed.

Key words: meconoquintupline, density functional theory (DFT), ab initio, molecular geometry, solvent effect, IR spectrum, thermodynamic property