Role of stilbenes in the natural durability of wood: Fungicidal structure-activity relationships

Abstract

The fungicidal bioactivity of a number of ( E)-4-hydroxy-3′- and/or 4 - ́ substituted stilbenes and related analogues was measured against the white-rot fungus Coriolus versicolor and the brown-rot fungi Gloeophyllum trabeum and Poria placenta using the agar plate technique. The bioactivity of didecyldimethylammonium chloride (DDAC), an effective wood preservative, was also determined for comparison purposes. Only DDAC and a (reduced) bibenzyl derivative with a 4′-hydrogen showed fungicidal activity against the white-rot fungus. Against the two brown-rot fungi all stilbenes with a 4′-hydrogen and also a (reduced) bibenzyl compound with a 4′-hydrogen had greater activity than DDAC. A quantitative structure-activity relationship study found that stilbene brown-rot bioactivity was linearly related to hydrophobicity. The results of this study and a review of the prior literature suggests that stilbene phytoalexins may be modified in vivo by partial methylation to further enhance their bioactivity.