π-stacking interactions between curcumin and aromatic ring of amino acids in amyloid fibrils: A theoretical study

[Display omitted] •π-interaction of curcumin with aromatic rings of three different amino-acids were studied by quantum mechanical methods.•Curcumin in diketo form has a greater π-interaction with aromatic rings of amino-acids.•Curcumin in keto-enol form is a better antioxidant than in diketo form.•Sum of electron densities at bond critical points and ring critical points are good descriptors for prediction of π-stacking interactions.•Tendency of curcumin to form intramolecular hydrogen bonds increases after π-stacking interaction. The aggregation of amyloid-β peptides into amyloid fibrils is considered as one of the possible causes of Alzheimer's disease. Curcumin is a well-known inhibitor for aggregation of Aβ1-42 peptides and has the ability to disintegrate preformed Aβ fibrils and amyloid plaques. This study provides an insight on the magnitude of π-stacking interactions between the aromatic AAs of Aβ and curcumin via quantum mechanical methods in gas phase and in water solvent. The results showed stacking interaction energies for CurK and amino acids are greater. The calculated charges on carbon atoms showed that B ring in CurE is more susceptible to π-stacking interaction. HOMO-LUMO energy gap showed that CurE is a better antioxidant than CurK. It was shown that the sum of electron densities, Ʃρ/n, calculated at BCPs and RCPs can be useful as descriptors for prediction of π-stacking interaction in the complexes.