桂皮醛應用為天然木材防腐劑之潛力評估

Abstract

防腐藥劑處理可有效地延長木材的使用年限，傳統的CCA（Chromated copper arsenate）木材防腐藥劑雖有很好的效果，但對人類及環境有毒性而逐漸被禁止使用，因此，尋找新的、有效的及安全的木材防腐藥劑便成為十分重要的議題。有鑑於此，本研究探討土肉桂（Cinnamomum osmophloeum）葉子精油中之主成分－桂皮醛抑制木材腐朽菌生長之機制，並進行桂皮醛處理材之木塊耐腐朽及耐白蟻試驗，同時測試桂皮醛處理材耐腐朽及耐白蟻之長效性；此外，亦評估桂皮醛在不同環境因子中之安定性。 由木塊耐腐朽及耐白蟻試驗結果得知，桂皮醛處理材經Lenzites betulina白腐菌、Laetiporus sulphureus褐腐菌腐朽及家白蟻（Coptotermes formosanus）啃食後之重量損失率皆顯著地小於未處理材之重量損失率，證實木材以桂皮醛含浸處理後能有效地減少腐朽菌及白蟻的危害，同時亦證明桂皮醛處理材長時間放置於常溫環境中，其耐腐朽及耐白蟻效果至少可維持一年。又由2種抗菌試驗方法（瓊脂稀釋法及紙片倒置法）及抗白蟻試驗得知，空間中桂皮醛含量愈高，抑制腐朽菌生長和白蟻忌避之活性愈佳，試驗結果證明桂皮醛抑制木材腐朽菌生長及白蟻之機制主要係由揮發性所造成。此外，根據桂皮醛安定性之評估結果得知，桂皮醛放置於常溫或不同酸鹼值環境中安定性良好。綜合上述試驗結果證明桂皮醛深具潛力應用為天然木材防腐藥劑。

To prolong the service life of wood effectively, treating wood with appropriate preservatives is necessary. Although traditional wood preservative, chromated copper arsenate (CCA), possessed strong antifungal property, it was phased out due to its toxicity to human being and environment. Therefore, it is imperative to find out a novel, effective, and safe wood preservative to replace conventional ones. Thus, in this study the major constituent of leaf essential oil from Cinnamomum osmophloeum, cinnamaldehyde, was used to explore its mechanisms of inhibiting the growth of wood-rot fungi. The fungi decay resistance, termite attack resistance and long-term effectiveness of cinnamaldehyde-treated wood were evaluated. In addition, the stability of cinnamaldehyde at different temperature and pH conditions was also investigated, respectively. Results from 90-day fungi (white-rot fungus Lenzites betulina and brown-rot fungus Laetiporus sulphureus) decay test and 30-day anti-termite (Coptotermes formosanus) test showed that weight losses of cinnamaldehyde-treated specimens were significantly lower than non-treated ones, revealing that cinnamaldehyde can endow wood block with excellent fungi decay resistance and termite attack resistance. In addition, the long-term effectiveness with excellent performance of cinnamaldehyde-treated wood was proved to last for 1 year at least. Also, from two antifungal methods (agar dilution method and inverted paper disc method) and anti-termitic test showed that the strong antifungal and antitermitic activities were observed when cinnamaldehyde released more amounts into headspace, indicating that mechanism of cinnamaldehyde inhibited the growth of wood-rot fungi and repelled the termites resulted from its volatility. Moreover, results from the evaluation of cinnamaldehyde stability revealed that cinnamaldehyde was stable at ambient temperature and various pH values. According to forgoing results, cinnamaldehyde possessed the great potential to be used as a natural wood preservative.