Abstract The common aspen is the most susceptible species to the action of wood‐destroying fungi among the forest‐forming species of the European North. The effect of wood‐destroying fungi on wood matter is a factor of biotic stress. The change in the physicochemical properties of slightly altered lignins extracted from sapwood and heartwood at the different stages of destruction of aspen wood is shown. Changes in the physicochemical properties such as functional composition, pK a values, oxidative potential of phenolic hydroxyl groups, macromolecular and electrophysical properties of lignin indicate the transformation of the natural polymer. Lignins of faute wood are characterized by an increased content of carbonyl groups. This leads to a change in redox properties of conjugated phenolic hydroxyl groups as reactivity centers of the macromolecule. The phenol‐quinone redox system in lignin is the main chemical barrier during enzymatic oxidation of the wood matrix. The changes in the free energy of oxidation of phenolic structures were calculated on the basis of the thermodynamic cycle. Transformation of the physicochemical properties of lignin is a protective mechanism of plants under biotic stress. © 2026 Society of Chemical Industry.
Khviyuzov et al. (Sun,) studied this question.