Study on Antifungal Mechanisms of Naturally Durable Wood

• Main Authors: Pin-Sheng Chen, 陳品昇
• Other Authors: Shang-Tzen Chang
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/16152254175115560214

碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 100 === To extend the wood service life, it is usually treated with preservatives. However, the traditional wood preservatives are highly toxic to environment and human beings. Using natural products as preservatives not only reduces toxicity but also slows down the impact on the environment. In this study the endemic durable species - Acacia confusa Merr. and Taiwania cryptomerioides Hay. were chosen to be investigated. Besides determining compounds with fungicidal activity, antioxidant activities and metal chelating capacity were carried out to explore the influences of active components on natural durable wood. The results showed extracts of A. confusa and T. cryptomerioides heartwood possessed excellent durability against white-rot fungus Lenzites betulina and brown-rot fungus Laetiporus sulphureus after 12 weeks decay resistance test while sapwood extracts didn’t exhibit any decay resistance ability. Antifungal and antioxidant activities of heartwood ethanolic extracts and their fractions were also carried out. The results obtained from agar plate method showed that A. confusa ethanolic extract and its three fractions exhibited no antifungal activity, whereas T. cryptomerioides heartwood ethanolic extracts had good antifungal activity and its n-hexane soluble fraction displayed the best antifungal activity among the four fractions. Six compounds were isolated using bioassay-guided fractionation from the n-hexane soluble fraction and their structures were identified, namely ferruginol, cedrol, T-cadinol, T-muurolol, α-cadinol, and hinokinin. In the antioxidant activity test, however, no significant antioxidant activity was observed with ethanolic extracts and its fractions of T. cryptomerioides heartwood. But ethanolic extracts from A. confusa heartwood had good antioxidant activity and its ethyl acetate soluble fraction showed excellent performance. Five compounds were isolated using bioassay-guided fractionation from the ethyl acetate soluble fraction and their structures were identified, namely protocatechuic acid, 7,8,3’,4’-tetrahydroxyflavanone, melanoxetin, transilitin, and okanin. In addition, fractions of heartwood extracts from A. confusa and T. cryptomerioides were soaked in sapwoods of Cryptomeria japonica D. Don and Acer serrulatum Hay. for 12 weeks decay resistance test. Three fractions of A. confusa extract performed good durability against L. s., and n-hexane soluble fraction of T. cryptomerioides extract was superior to other fractions. Sapwoods of A. serrulatum soaked with fractions of two extracts showed no significant resistance to L. b.. Natural durability of A. confusa should be associated with its crude extract. However, the extract from A. confusa didn’t show toxic effectiveness but had good antioxidant activity, which lead to the increase in decay resistance to L. s.. Therefore, the natural durability of A. confusa may be attributable to its antioxidant action. Natural durability of T. cryptomerioides is significantly associated with its active ingredients in the n-hexane soluble fraction whose main action is antifungal rather than antioxidant activity. Therefore, the naturally durable mechanism of T. cryptomerioides is attributable to the active compounds which act as fungicides to prevent deterioration caused by wood rot fungi.