Effects of <i>Cunninghamia lanceolata</i> Heartwood Extracts on the Wood Decay Resistance

Abstract

In this study, three extractives from China-fir heartwood were obtained by sequential extraction processes with hexane, ethyl acetate and methanol. The antifungal activities of three extractives against two wood decay fungi (Trametes versicolor and Gloeophyllum trabeum) and two wood stain fungi (Paecilomyces variotii and Aspergillus niger) were evaluated with digging-hole method. The results showed that none of the three extracts had good antifungal activities against these four fungi. Among the three extracts, the hexane one was the most effective and the methanol extract was the second. The ethyl acetate extract, to some degree, stimulated the growth of wood decay fungi. Judging from antifungal activities of extracts, the combination of extracts rather than any single compound is important for China-fir durability. The cubes of China-fir heartwood went through a sequential extraction processes with hexane, ethyl acetate and methanol in Soxhlet extractor. The wood decay resistances of non-extracted and extracted heartwood blocks against Trametes versicolor and Gloeophyllum trabeum were evaluated after steam sterilization according to the Chinese standard method. Non-extracted heartwood blocks were resistant to Trametes versicolor but experienced substantial weight losses when exposed to Gloeophyllum trabeum. Weight losses increased after hexane extraction, but then declined markedly after ethyl acetate extraction. The possible explanation for the declined weight losses of ethyl acetate extracted blocks could be that some components which stimulated the growth of these fungi, especially Trametes versicolor were extracted by ethyl acetate. After extraction with methanol, weight losses of the blocks by Gloeophyllum trabeum increased dramatically but weight losses of the blocks by Trametes versicolor were similar to those of the ethyl acetate extracted blocks.