Tanshinone I and isotanshinone I: The effects of media, isomerization and complexation on structural and electronic parameters

Publication date: 1 September 2017 Source:Computational and Theoretical Chemistry, Volume 1115 Author(s): Fatemeh Pakzad, Ali Ebrahimi, Abolfazl Azizi In the present study, structural and electronic parameters of two diterpenoid quinones in Salvia miltiorrhiza, tanshinone I (TS1) and isotanshinone I (IS1), and their complexes with Mg2+ cation, TS1-Mg2+ and IS1-Mg2+, have been investigated by the means of quantum mechanical calculations in the gas phase, DMSO and water solvent. Molecular electrostatic potential (MEP) around the O atoms has been used in order to predict the nucleophilic active sites on complexation with Mg2+ cation. The conformational/complexation energy, Econ/ΔEfor, become more negative with the increase/decrease in the polarity of media. Furthermore, a negligible difference is observed between the Econ values of diterpenoids, and also the ΔEfor values of complexes in DMSO and water solvent, while the differences are higher between those calculated in the solution media and gas phase. In each media, Econ (IS1) and ΔEfor (TS1-Mg2+) are more negative than Econ (TS1) and ΔEfor (IS1-Mg2+), respectively. Complexation increases the stability and makes notable changes in structural and electronic properties of diterpenoids. Some results of population analysis, geometrical properties, theoretically estimated aromaticity indices and total dipole moments can be useful descriptors for prediction of the trend of ΔEfor and Econ values of the complexes. In general...

Source: Computational and Theoretical Chemistry - July 15, 2017 Category: Chemistry Source Type: research