Flavonoids of Zinnia elegans: Chemical profile and, in vitro antioxidant and in silico anti-COVID-19 activities

ABSTRACT

Chemical profiles of total alcohol extract and various derived fractions of aerial parts of Zinnia elegans were studied. Accordingly, eight flavonoids were isolated from the ethyl acetate derived fraction based on the antioxidant assay-guided purification, using DPPH and phosphomolybdate complex assays. Eventually, the binding affinities and features of the eight isolated flavonoids were investigated using the molecular docking technique towards SARS-CoV-2 and human targets –namely main protease (Mpro), papain-like protease (PLpro), RNA-dependent RNA polymerase (RdRp), receptor-binding domain (RBD), helicase (NSP13), human angiotensin‐converting enzyme 2 (ACE2), and human neuropilin-1 (NRP1). Docking calculations unveiled the surpass binding affinity of glabrisoflavone with Mpro, PLpro, RdRp, RBD, NSP13, ACE2, and NRP1, with docking scores of −9.2, −7.4, −6.9, −6.9, −8.5, −9.0, and −7.6 kcal/mol, respectively. Binding mode analysis manifested the capability of glabrisoflavone to form several hydrogen bonds with the key amino acid residues inside the active sites of the targets. Besides, 25 ns molecular dynamics (MD) simulations combined with molecular mechanics-generalized Born surface area (MM-GBSA) binding energy calculations were executed to inspect the binding affinity of glabrisoflavone and compared to an anti-HIV-1 protease inhibitor (darunavir). MM-GBSA calculations demonstrated greater glabrisoflavone affinity for the PLpro, RdRp, RBD and NRP1 over darunavir. Nevertheless, MM-GBSA calculations displayed equal or lower glabrisoflavone affinity against Mpro, NSP13 and ACE2 compared to darunavir. The current study obviously emphasizes the fitness of the glabrisoflavone as an auspicious clinical drug candidate for further development and future in vivo and in vitro evaluations towards viral targets and human targets.