Synthesis and structural characterization of a 8-hydroxyquinoline derivative coordinated to Zn(II)

Potential molecular and graphene oxide chelators to dissolve amyloid-β plaques in Alzheimer's disease: a density functional theory study

The onset of Alzheimer's disease (AD) is caused by amyloid-β (Aβ) aggregation. Elevated levels of metals, specifically copper, zinc, iron, and aluminum, accumulate in senile Aβ; plaque deposits, disrupting normal brain homeostasis and cognitive functions. In this investigation, we studied the potential of several molecular and graphene oxide chelators to be used for future AD research and chelation therapy. To understand the interactions between selected metals (Cu, Zn, Fe, and Al), the Aβ peptide, and various potential metal chelating compounds, we implemented the density functional theory (DFT) method to calculate the binding energies of each metal-molecule complex. The binding energy of each metal-chelator complex was compared with that of the metal-Aβ compound to determine the chelation potential of the selected chelator. The potential chelating agents studied were 8-hydroxyquinoline-2-carboxaldehyde isonicotinoyl hydrazone (INNHQ), 8-hydroxyquinoline-2-carboxaldehyde 2-furoyl hydrazone (HQFUH), quercetin, and graphene oxide (GO). Our calculated binding energies revealed that the HQFUH molecule holds direct ability to chelate copper, zinc, iron, and aluminum. In addition, the GO complex with a 12.5% oxygen concentration demonstrates aluminum chelation ability. Our results demonstrate that HQFUH and GO can be used in future AD drug development research and therapy to target toxic metal-Aβ interactions and reduce Aβ aggregation.

Electronic investigation of the effect of substituents on the SOD mimic activity of copper (II) complexes with 8-hydroxyquinoline-derived ligands

Density functional theory (DFT) calculations were used to study the superoxide dismutase (SOD) mimic activity of two Cu²⁺ complexes with ligands derived from 8-hydroxyquinoline (8-HQ). Electron-donating and -withdrawing substituent groups were inserted into the structures to verify changes in the reactivity. The theoretical parameters obtained were compared and validated with the experimental data available. The results showed that the reduction process occurs with greater participation of the 8-HQ ligand and the oxidation step occurs with participation of the copper atom in the complexes, where the electron received during the reduction step is used to reduce the Cu²⁺ to Cu⁺. The calculated electronic affinity showed good correlation with the experimental mimetic activity, and the analysis of this property, of total charge and of molecular orbitals indicated an increase in the mimetic activity with the insertion of electron-withdrawing substituent groups in the structures.

Structural Determination of Antioxidant and Anticancer Flavonoid Rutin in Solution through DFT Calculations of 1H NMR Chemical Shifts

As the knowledge of the predominant molecular structure of antioxidant and anticancer flavonoid rutin in solution is very important for understanding the mechanism of action, a quantum chemical investigation of plausible rutin structures including solvent effects is of relevance. In this work, DFT calculations were performed to find possible minimum energy structures for the rutin molecule. ¹H NMR chemical shift DFT calculations were carried out in DMSO solution using the polarizable continuum model (PCM) to simulate the solvent effect. Analysis of the experimental and theoretical ¹H NMR chemical shift profiles offers a powerful fingerprint criterion to determine the predominant molecular structure in solution. Therefore, our aim is to find the best match between experimental (in DMSO‐d) and theoretical (PCM–DMSO) ¹H NMR spectrum profiles. Among 34 optimized structures located on the potential energy surface, we found that structure 32, with a B‐ring deviated 30° from a planar configuration (geometry usually assumed for polyphenols), showed an almost perfect agreement with experimental the ¹H NMR pattern when compared to the corresponding fully optimized planar geometry. This structure is also predicted as the global minimum based on room‐temperature Gibbs free energy calculations in solution and, therefore, should be experimentally observed. This is new and valuable structural information regarding structure–activity relationship studies, and such information is hard to obtain by experimentalists without the aid of the X‐ray diffraction technique.