Durability of Angiosperm Heartwood: The Importance of Extractives

Analysis of osage orange (Maclura pomifera) heartwood extractives showed that two compounds were present at much higher levels than previously reported, the flavanonol dihydromorin (2.51%) and the stilbene oxyresverauol (2.65%). All compounds present in osage orange heartwood that were tested bad low activity against wood-decaying fungi. The agar plate test showed no synergistic effect, but the soil block test using white-rot fungi suggested synergism. The high durability of osage orange heartwood may be due to the large amounts of oxyresveratrol and dihydromorin. High levels of one or two monomeric compounds may also explain the exceptionally good durability of black locust and red mulberry heartwood.