Mechanism of decay resistance of heartwood extracts from Acacia confusa against the brown-rot fungus Laetiporus sulphureus

Acacia confusa is an indigenous plantation species in Taiwan, and its heartwood has excellent decay resistance capability. The aim of this study is to investigate the resistance mechanisms of heartwood extracts from A. confusa against Laetiporus sulphureus (brown-rot). Results from wood block decay resistance tests indicate that aqueous crude extract and its three soluble fractions can significantly decrease the weight loss of wood blocks caused by L. sulphureus. However, none of the extracts can inhibit the growth of L. sulphureus on agar plate test. The performance of decay resistance from three soluble fractions is consistent with their antioxidant activities (DPPH free radical scavenging activity, reducing power and ferrous ion chelating ability). 3,4-Dihydroxybenzoic acid (3,4-DHBA), the compound present in three soluble fractions, exhibited excellent antioxidant activities and was proven to have excellent decay resistance ability against L. sulphureus. These findings suggest that 3,4-DHBA may be responsible for the inhibition of hydroxyl radical formation from Fenton reaction caused by L. sulphureus. Thus, 3,4-DHBA has good potential to be used as a novel and environmentally benign wood preservative.