白千層花與葉子精油抗真菌活性之探討

Abstract

白千層屬（Melaleuca）植物為澳洲及東南亞地區重要的林產資源，常作為殺菌驅蚊、抗發炎、抗氧化及治療感冒疼痛等之藥用植物。其中，白千層（M. leucadendra）對環境適應力強，生長快速，許多國家大量栽種作為防風林與行道樹，為全球常見的植物。白千層花香氣濃郁，葉子有油腺點，能萃取出豐富的精油。本研究結果證實，白千層花和葉子精油的主成分大致相同，為α-Pinene、Limonene、1,8-Cineole、α-Terpineol、Viridiflorol及Ledol，其中，白千層花精油最多的主成分為Viridiflorol（350.3 mg/g EO），其次是Ledol（188.7 mg/g EO）；葉子精油主成分為1,8-Cineole（365.7 mg/g EO），其次是Viridiflorol（225.3 mg/g EO）。 本研究評估白千層花和葉子精油抗黴菌及木材腐朽菌之活性試驗，結果顯示白千層花及葉子精油抑制Aspergillus niger之效果不好，但能有效抑制白腐菌Lenzites betulina及褐腐菌Laetiporus sulphureus。此外，花精油的抑制效果較葉子精油好，對L. betulina及L. sulphureus之IC50值分別為114及40 μg/mL，證實白千層花精油具有潛力作為木材防腐劑。此外，白千層花精油以瓊脂稀釋法之抗木材腐朽菌效果較薰蒸法佳。進一步分析6種主成分之抗木材腐朽菌活性，結果顯示有效抗菌成分主要來自Viridiflorol，對白腐菌L. betulina及褐腐菌L. sulphureus之IC50值分別為41及24 μg/mL。 此外，本研究探討氣乾前後、萃取3或6 h及不同季節對白千層花及葉子精油收率及抗菌成分之影響，結果顯示花精油於這3種不同萃取條件下的收率及抗菌成分皆無顯著差異。白千層葉子精油收率於夏天較高，冬天較低，但不會受氣乾及萃取時間延長之影響。雖然白千層葉子精油中的抗菌成分Viridiflorol蒸餾6 h之萃取量較多，但並未達3 h之萃取量之2倍，因此，仍以萃取3 h較符合成本效益。 最後，本研究評估白千層花及葉子精油之萃取效益，由於白千層花精油中的抗菌成分較多，抗菌效果優於葉子精油，因此，花精油較適合作為木材防腐劑。然而，白千層葉子精油雖然抗木材腐朽菌效果略差，但其抗菌有效成分與花精油皆為Viridiflorol，且葉子精油收率高，可取代花精油作為抗菌成分分離及收集之用途。

As medicinal plants used for fungicides, antiseptics, repellents, anti-inflammation, analgesics, anti-inflammatory and cold drugs, Melaleuca species plays an important role on forest resources in Australia. Among them, M. leucadendra, one of the common plants in the world, is planted as a windbreak or street tree due to strong adaptation ability and fast growing. M. leucadendra has strong-scented flowers and oil-gland dotted leaves which can be extracted for abundant essential oils (EO). The main constituents of the flower and leaf essential oils obtained in this study are the same, including α-pinene, limonene, 1,8-cineole, α-terpineol, viridiflorol, and ledol. However, The content of viridiflorol (350.3 mg/g EO) is the highest in the flower esseatial oil followed by ledol (188.7 mg/g EO), while the contenct of 1,8-cineole (365.7 mg/g EO) is the highest in the leaf essential oil followed by viridiflorol (225.3 mg/g EO). Anti-mold and Anti-wood-rot-fungi treatments were investigated in the study. The results show flower and leaf essential oils of M. leucadendra are unable to inhibit the growth of Aspergillus niger, but they, especially the flower essential oil, have effective inhibition against white-rot Lenzites betulina and brown-rot Laetiporus sulphureus. The IC50 values of the flower essential oil are 114 μg/mL against L. betulina and 40 μg/mL against L. sulphureus, which shows potential biological activity as a wood preservative. Besides, the antifungal activity of flower essential oil in agar dilution test is better than in fumigation test. In further analysis, it is from viridiflorol that the anti-fungal activity is in the flower and leaf essential oils of M. leucadendra. The IC50 values of viridiflorol are 41 and 24 μg/mL against white-rot L. betulina as well as L. sulphureus, respectively. The study also examined the influence of extraction conditions, including drying, time, and seasons on the yield and chemical contents of flower and leaf essential oils from M. leucadendra. The results find that the yield and chemical contents of the flower essential oil are not siginificantly different under different conditions above. In contrast, the leaf essential oil has high yield in summer and low yield in winter. Additionally, the content of viridiflorol in the leaf essential oil obtained from 6-h distillation is less than twice higher than that from 3-h distillation. Therefore, 3-h distillation is more cost-effective. In conclusion, the extraction effectiveness is also evaluated in the study. The flower essential oil of M. leucadendra is a better wood preservative owing to good antigunal activity and high amount of viridiflorol , while the leaf is better for separating and collecting viridiflorol because of high essential oil yield.