Antifungal constituents responsible for the high wood decay resistance of Syringa reticulata: identification of paulownin, sesamin and eudesmols

Japanese lilac ( Syringa reticulata ) was reportedly used as a structural material in prehistoric Hokkaido, suggesting that this species was empirically recognized as suitable for structural applications. In addition to its superior mechanical properties, previous studies demonstrated its remarkably high resistance to fungal decay, implying the presence of antifungal constituents enabling its decay resistance. In this study, two lignans, namely paulownin and sesamin, and sesquiterpene alcohols, i.e., eudesmols, were identified through bioassay-guided fractionation as antifungal constituents active against white-rot fungi. The combined antifungal activity of the isolated compounds could partly explain the activity of the original extract but did not fully reproduce the total activity of the heartwood. These results suggest that the high decay resistance of S. reticulata is achieved through the combined effects of multiple components and/or synergistic interactions among active constituents.