Investigating the behaviors of corticosterone hormone in different solvents by using DFT calculations and experimental data

Abstract

In this work, structural, electronic, topological and vibrational properties of corticosterone hormone have been investigated in aqueous, ethanol and methanol solutions by using DFT calculations and experimental available infrared, attenuated total reflectance (ATR), Raman and Ultraviolet spectra. The properties predicted in the different solvents at the B3LYP/6-31G* level of theory were compared with those obtained in gas phase and, with others reported for steroids species at the same level of theory. The universal solvation model has evidenced higher solvation energy for corticosterone in aqueous solution and a higher value in methanol, as compared with the corresponding values to equilenin, equilin and estrone steroids in the same medium. Higher Mulliken charges on O atoms of C=O group of side chain are observed in the three solvents than the corresponding to C=O group of ring A while the MK charges on O atoms of OH group of ring C present higher values than the corresponding to O atoms of OH group of side chain. The natural bond orbital (NBO) studies have revealed a low stability of corticosterone in aqueous solution, as compared with the values in ethanol and methanol solutions, in total agreement with the higher solvation energy and dipole moment in this medium. On the other hand, the atoms in molecules (AIM) analyses support the lower stabilities of corticosterone in the three solutions because only five H bonds interactions different from of gas phase where six interactions are observed. The gap values suggests that corticosterone is most reactive in aqueous solution than the other solutions, as supported by the low stability and higher solvation energy and dipole moment values in this medium. This study shows clearly that the steroid species most reactive, equilenin and corticosterone, are characterized by a high global electrophilicity index value and low nucleophilicity index. Reasonable correlations in the predicted IR, Raman and UV spectra were observed, as compared with the corresponding experimental ones. Additionally, the complete vibrational assignments of all 159-vibration modes of corticosterone together with the harmonic force fields and force constants in the different media are for the first time presented.