Pyroligneous acids (PA) from hardwood, softwood, and bamboo significantly disinfected encephalomyocarditis virus (EMCV). Twenty-five kinds of phenolic derivatives in the PAs were identified and quantified. The total amounts of phenolic compounds in bamboo PA is higher than those in the PAs from softwood and hardwood. Phenol, 2-methoxyphenol, 2-methoxy-4-methylphenol, and 2-methoxy-4-ethylphenol are the most abundant compounds in the PAs examined. The activities of all the phenolic compounds against the encephalomyocarditis virus were assessed. The number of phenolic hydroxyl groups significantly affects the antiviral activity, and catechol and its derivatives exhibit higher viral inhibition effects than other phenolic derivatives. In addition, substituents affect the antiviral activity of the compounds. Phenolic compounds with a methyl group show higher activities than with a methoxyl group (e.g., 2-methylphenol > 2-methoxyphenol). Moreover, the relative position of functional groups also plays a key role in the viral inhibition activity (e.g., 2,6-dimethoxyphenol > 3,4-dimethoxyphenol). Thus, PAs contain phenol derivatives with considerable structural diversity and viral inhibition activities, providing a new strategy for virus-inactivation treatment through the optimization of PA-derived phenol structures.

The production of bioactive agents from lignocelluloses has received limited attention because plant cell walls are essentially non‐bioactive. In this study, a chemical reaction is reported, which produces a lignin‐derived antiviral substance from sugarcane bagasse by microwave heating at 200 °C in aqueous glycerol containing 0.5 % H2SO4. The purified fraction, designated as FR200, strongly inhibited the replication of encephalomyocarditis virus (EMCV) in L929 cells without cytotoxicity. HSQC NMR spectra demonstrated that the principal interunit linkages in the native lignin were cleaved by the reaction. Gel permeation chromatography (GPC) and pyrolysis‐GCMS revealed that FR200 is composed of oligomeric lignin with a weight average molecular weight of approximately 2000. When the bagasse was reacted at lower temperatures, 140 °C and 160 °C, the native lignin substructures were partially retained and the antiviral activity significantly decreased. The results thus indicate that the antiviral activity emerged through severe alteration of the native lignin structure. Furthermore, it was revealed that the antiviral lignin inactivated the EMCV virions through direct contact, as the innate immune system of L929 was not activated by FR200 treatment, and no antiviral activity was found when L929 was pre‐treated with the lignin before viral infection.

The structure-related antiviral activities of catechol and derivatives were investigated. A new strategy for producing antiviral compounds was proposed.

Virus pandemics pose a threat to human life. In this study, we developed a simple method for the conversion of woody biomass into antiviral substances. Beech wood was decomposed by microwave acidolysis in 0.5% aq H2SO4 and fractionated by silica gel chromatography. The obtained fractions exhibited strong antiviral activity against encephalomyocarditis virus (EMCV) without cytotoxicity. Structural analyses revealed that the separated antiviral substances were lignin–carbohydrate complexes with molecular weight in the range of 2600–3900, containing 86.8–90.4% lignin and 3.1–6.1% carbohydrates. Moreover, the native β-O-4 linkages were considerably cleaved by microwave acidolysis, whereas the β–β and β-1 interlinkages remained partially unchanged. A signal corresponding to the α-ether linkage between the lignin and carbohydrates was observed in the heteronuclear single-quantum coherence nuclear magnetic resonance spectra. The cleavage of the carbohydrate chains by hemicellulase significantly reduced the antiviral activity, suggesting that the carbohydrate moiety played a critical role in the inactivation of EMCV. This research provides a green strategy for the production of huge amounts of antiviral substances from a sustainable bio-resource.

No abstract