Bioactive Compositions of Cinnamon (Cinnamomum verum J. Presl) Extracts and Their Capacities in Suppressing SARS-CoV-2 Spike Protein Binding to ACE2, Inhibiting ACE2, and Scavenging Free Radicals

Cinnamon (Cinnamomum verum J. Presl) bark and its extracts are popular ingredients added to food and supplement products. It has various health effects, including potentially reducing the risk of coronavirus disease-2019 (COVID-19). In our study, the bioactives in cinnamon water and ethanol extracts were chemically identified, and their potential in suppressing SARS-CoV-2 spike protein-angiotensin-converting enzyme 2 (ACE2) binding, reducing ACE2 availability, and scavenging free radicals was investigated. Twenty-seven and twenty-three compounds were tentatively identified in cinnamon water and ethanol extracts, respectively. Seven compounds, including saccharumoside C, two emodin-glucuronide isomers, two physcion-glucuronide isomers, and two type-A proanthocyanidin hexamers, were first reported in cinnamon. Cinnamon water and ethanol extracts suppressed the binding of SARS-CoV-2 spike protein to ACE2 and inhibited ACE2 activity in a dose-dependent manner. Cinnamon ethanol extract had total phenolic content of 36.67 mg gallic acid equivalents (GAE)/g and free radical scavenging activities against HO• and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS•+) of 1688.85 and 882.88 μmol Trolox equivalents (TE)/g, which were significantly higher than those of the water extract at 24.12 mg GAE/g and 583.12 and 210.36 μmol TE/g. The free radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) of cinnamon ethanol extract was lower than that of the water extract. The present study provides new evidence that cinnamon reduces the risk of SARS-CoV-2 infection and COVID-19 development.