Anti-SARS-CoV-2 activity of microwave solvolysis lignin from woody biomass

The global pandemic caused by the novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has had profoundly detrimental effects on our society. To combat this highly pathogenic virus, we turned our attention to an abundant renewable natural aromatic polymer found in wood. Through a chemical modification of Eucalyptus and Japanese cedar wood via acidic microwave solvolysis in equivolume mixture of 2 % (w/w) aqueous H₂SO₄, ethylene glycol, and toluene at 190 °C. Subsequently, we separated the resulting solvolysis products through extractions with toluene, ethyl acetate, and ethanol. Among these products, the ethyl acetate extract from Eucalyptus wood (eEAE) demonstrated the highest inhibition effects against the novel SARS-CoV-2. We further divided eEAE into four fractions, and a hexane extract from the ethanol-soluble portion, termed eEAE3, exhibited the most substantial inhibitory rate at 93.0 % when tested at a concentration of 0.5 mg/mL. Analyzing eEAE3 using pyrolysis gas chromatography-mass spectrometry revealed that its primary components are derived from lignin. Additionally, ¹H-¹³C edited-heteronuclear single quantum coherence nuclear magnetic resonance analysis showed that the solvolysis process cleaved major lignin interunit linkages. Considering the abundance and renewability of lignin, the lignin-derived anti-SARS-CoV-2 agent presents a promising potential for application in suppressing infections within our everyday environment.