Solvent Effects on the Cleavage of Emodin’s Non H-bonded O-H Link: A Theoretical Study

Abstract

Although Emodin is a well-known natural antioxidant, not much is documented on how the cleavage of its free O-H bond (non-hydrogen bond donor) is affected by solvation. Herein, we report on a Density Functional Theory (DFT) study of solvent effects on the enthalpy of homolytic and heterolytic cleavage of this bond in the most stable conformer of emodin. This cleavage results in the release of an atom of hydrogen from emodin, whatever the mechanism adopted. ¶The B3LYP functional has been associated with the 6-311++G** basis set in this work while ¶solvent effects have been investigated via the IEF-PCM approach. ¶Our results show that, contrary to available research which indicates that solvation modifies the antioxidant mechanism, emodin’s antioxidant mechanism remains unaltered throughout transition from the gas to the solvent phase. ¶This observation is peculiar to emodin among the plethora of known antioxidant molecules. ¶Emodin preferentially exerts its antioxidant effect through the homolytic hydrogen atom transfer mechanism.