In silico evaluation of food-derived carotenoids against SARS-CoV-2 drug targets: Crocin is a promising dietary supplement candidate for COVID-19.

The current COVID-19 pandemic is severely threatening public healthcare systems around the globe. Some supporting therapies such as remdesivir, favipiravir, and ivermectin are still under the process of a clinical trial, it is thus urgent to find alternative treatment and prevention options for SARS-CoV-2. In this regard, although many natural products have been tested and/or suggested for the treatment and prophylaxis of COVID-19, carotenoids as an important class of natural products were underexplored. The dietary supplementation of some carotenoids was already suggested to be potentially effective in the treatment of COVID-19 due to their strong antioxidant properties. In this study, we performed an in silico screening of common food-derived carotenoids against druggable target proteins of SARS-CoV-2 including main protease, helicase, replication complex, spike protein and its mutants for the recent variants of concern, and ADP-ribose phosphatase. Molecular docking results revealed that some of the carotenoids had low binding energies toward multiple receptors. Particularly, crocin had the strongest binding affinity (-10.5 kcal/mol) toward the replication complex of SARS-CoV-2 and indeed possessed quite low binding energy scores for other targets as well. The stability of crocin in the corresponding receptors was confirmed by molecular dynamics simulations. Our study, therefore, suggests that carotenoids, especially crocin, can be considered an effective alternative therapeutics and a dietary supplement candidate for the prophylaxis and treatment of SARS-CoV-2. PRACTICAL APPLICATIONS: In this study, food-derived carotenoids as dietary supplements have the potential to be used for the prophylaxis and/or treatment of SARS-CoV-2. Using in silico techniques, we aimed at discovering food-derived carotenoids with inhibitory effects against multiple druggable sites of SARS-CoV-2. Molecular docking experiments against main protease, helicase, replication complex, spike protein and its mutants for the recent variants of concern, and ADP-ribose phosphatase resulted in a few carotenoids with multitarget inhibitory effects. Particularly, crocin as one of the main components of saffron exhibited strong binding affinities to the multiple drug targets including main protease, helicase, replication complex, mutant spike protein of lineage B.1.351, and ADP-ribose phosphatase. The stability of the crocin complexed with these drug targets was further confirmed through molecular dynamics simulations. Overall, our study provides the preliminary data for the potential use of food-derived carotenoids, particularly crocin, as dietary supplements in the prevention and treatment of COVID-19.