Structure and electronic properties of the HA-CUR conjugate: An insight from the DFT perspective

Abstract

In this article, we are reporting the results of the first detailed Density Functional Theory (DFT) study of the structure of the hyaluronic acid-curcumin (HA-CUR) compound. The molecular orbitals (MOs), frontier molecular orbitals (FMOs, i.e., energies of the FMOs and HOMO/LUMO gaps), and molecular electrostatic potential (MEP) of the compound have been investigated using the Gaussian 09 package using the hybrid functional B3LYP with the split-valence polarized 6-311G(d,p) basis set (B3LYP/6-311G(d,p) approach). In addition, the NBO (Natural Bond Orbital) charge analysis and NBO bonding analysis for the HA-CUR complex have been performed. The structures of the HA and CUR moieties inside the HA-CUR complex are found noticeably different from their free molecules, and the LUMO of the HA-CUR complex is noticeably stabilized compared to the HA LUMO and to the CUR LUMO, which leads to the noticeable closure of the HA-CUR HOMO/LUMO gap compared to the HA gaps and CUR water-computed gap. The detailed studies carried out on the HA-CUR complex in different aspects will definitely be useful for the researchers working in the area of the novel drug design and pharmaceutical chemistry.