Curcumin as a potential multiple-target inhibitor against SARS-CoV-2 infection: A detailed interaction study using quantum chemical calculations

Curcumin is one of the important naturally occurring compounds having several medicinal properties such as: antiviral, antioxidant, antifibrotic, antineoplastic as well as anti-inflammatory. SARS-CoV-2 has emerged as infectious virus, which severely infected a large number of people all over the world. Many efforts have been made to prepare novel antiviral compound, but it is still challenging. Naturally occurring compound, curcumin, can be used as an alternative to antiviral compound against SARS-CoV-2. Its effect against SARS-CoV-2 is already highlighted in the literature. But the quantitative study of its interaction with various precursors of SARS-CoV-2 is not reported till date. This paper reports the interaction of curcumin with angiotensin-converting enzyme2, transmembrane serine protease 2, 3-chymotrypsin-like protease and papain-like protease through molecular docking and quantum chemistry calculations to achieve quantitative understanding of underlying interactions. Here the conformational flexibility of curcumin is also highlighted, which helps it to accommodate in the four different docking sites. The study has been performed using calculations of geometrical parameter, atomic charge, electron density, Laplacian of electron density, dipole moment and the energy gap between highest occupied and lowest unoccupied molecular orbitals. The non- -covalent interaction (NCI) analysis is performed to visualize the weak interaction present in the active sites. Combinedly molecular docking and detailed quantum chemistry calculations revealed that curcumin can be adopted as a potential multiple-target inhibitor against SARS-CoV-2.