Oleuropein aglycone aldehyde as a SARS-CoV-2 main protease inhibitor
Md Sofequl Islam Mukim, Sangeun Jeon, Bohyeon Kim, Shivani Rajoriya, Divya Misra, Hee-Ju Lee, Jaeyoung Kwon, Jin Wook Cha, Cheol‐Ho Pan, Won-Keun Kim, Seungtaek Kim, Dae‐Geun Song · Phytomedicine · 2026
Background The evolution of SARS-CoV-2 emphasizes the urgent need for broad-spectrum antivirals targeting conserved viral enzymes such as the main protease (M pro ). Olea europaea (European olive) and Canarium album (Chinese olive) contain diverse bioactive phytochemicals with potential antiviral properties, yet their mechanistic relevance to SARS-CoV-2 remains undefined. Purpose To identify bioactive phytochemicals from European and Chinese olives and explore their mechanisms in inhibiting SARS-CoV-2 M pro . Methods Sixty-six phytochemicals were screened using a FRET-based M pro assay. Potent candidates were further evaluated by IC 50 determination, enzyme kinetics, cytotoxicity, and live-virus assays. Binding interactions were characterized using ITC and STD-NMR, while stereochemistry-dependent behavior was examined through chiral chromatographic analysis, molecular docking and molecular dynamics simulations. Results Five compounds—Oleuropein Aglycone Aldehyde (OAA), Hydroxytyrosol (HT), Oleuropein (OL), Oleuropeinic acid (OPA), and Oleuroside (OS)—displayed significant M pro inhibition (IC 50 : 4.8–15.7 μM; K i : 3.4–18.0 μM). OAA was the most potent inhibitor through a competitive mechanism with antiviral activity against the ancestral strain (EC 50 = 19.8 μM) and Omicron/Delta variants. ITC confirmed 1:1 binding (K d = 13.5 μM), and STD-NMR showed that both 8S and 8R diastereomers interact with M pro . Molecular modeling supported stable engagement within the catalytic pocket, where the 8S adopted an extended, multi-contact orientation, and the 8R occupied a compact subpocket. Conclusion OAA is a natural SARS-CoV-2 M pro inhibitor exhibiting stable binding, stereochemical preference, and cross-variant antiviral activity. Its defined biochemical mechanism and stable structural engagement position OAA as a promising scaffold for antiviral development.