Exploratory conformational study of (+)-catechin. Modeling of the polarizability and electric dipole moment.

The extension of the study of the conformational space of the structure of (+)-catechin at the B3LYP/6-31G(d,p) level of theory is presented in this paper. (+)-Catechin belongs to the family of the flavan-3-ols, which is one of the five largest phenolic groups widely distributed in nature, and whose biological activity and pharmaceutical utility are related to the antioxidant activity due to their ability to scavenge free radicals. The effects of free rotation around all C-O bonds of the OH substituents at different rings are taken into account, obtaining as the most stable conformer, one that had not been previously reported. One hundred seven structures, and a study of the effects of charge delocalization and stereoelectronic effects at the B3LYP/6-311++G(d,p) level are reported by natural bond orbital analysis, streamlining the order of these structures. For further analysis of the structural and molecular properties of this compound in a biological environment, the calculation of polarizabilities, and the study of the electric dipole moment are performed considering the whole conformational space described. The results are analyzed in terms of accumulated knowledge for (4α → 6″, 2α → O → 1″)-phenylflavans and (+)-catechin in previous works, enriching the study of both types of structures, and taking into account the importance of considering the whole conformational space in modeling both the polarizability and the electric dipole moment, also proposing to define a descriptive subspace of only 16 conformers.