伽羅木醇型土肉桂葉子供作芳香材料可行性之探討

Abstract

伽羅木醇型土肉桂（Cinnamomum osmophloeum ct. linalool）為臺灣原生土肉桂中的一種化學品系，其葉子精油及主成分S-(+)-Linalool皆具有良好的抗焦慮活性。本研究目的為探討伽羅木醇型土肉桂葉子供作芳香材料之可行性，首先，本研究嘗試建立新的微量萃取方法-超音波輔助微量萃取法（Ultrasound-assisted microextraction, UAME）萃取葉子精油；接著，探討植株生理變異對葉子精油成分含量之影響；另外，亦評估葉子精油及其主成分S-(+)-Linalool之安定性。 探討精油最適萃取條件之試驗結果顯示，水蒸餾法（Hydrodistillation, HD）是使用大量葉子（10 g）並添加乙醚（Diethyl ether）於Clevenger裝置萃取30 min；而UAME則是使用微量葉子（10 mg），添加正己烷（n-Hexane）後利用超音波輔助萃取1 min，此條件萃得的S-(+)-Linalool含量（28.3 ± 0.5 mg/g leaf）與HD萃得的相當（26.9 ± 2.7 mg/g leaf），顯示UAME可應用於快速萃取分析伽羅木醇型土肉桂葉子的S-(+)-Linalool含量。 接著，本研究分別利用HD與UAME萃取葉子精油，探討繁殖方式（扦插、嫁接、種子及組織培養）、單株差異（6株嫁接繁殖植株）、季節（春、夏、秋及冬）變化及葉子成熟度（嫩葉、半成熟葉及成熟葉）4種生理變異因子對精油成分含量之影響。試驗結果顯示，扦插、嫁接、種子及組織培養等4種方式繁殖之植株中，扦插及嫁接繁殖葉子的S-(+)-Linalool含量及精油收率最高；單株差異對嫁接繁殖植株葉子的精油成分含量並無顯著影響；季節變化分析結果顯示，四季變化對葉子S-(+)-Linalool含量的影響相當低，四季採收葉子的精油收率高（≥ 2.9%）且皆含有大量S-(+)-Linalool（≥ 27.0 mg/g leaf）。此外，3種成熟度葉子，僅成熟葉子含有大量S-(+)-Linalool。由上述結果得知，全年皆可採收伽羅木醇型土肉桂之成熟葉子，供作獲取大量S-(+)-Linalool之來源。 另由葉子精油及S-(+)-Linalool的安定性試驗結果顯示，氣乾與烘乾（30、45及60oC）對葉子精油的化學組成均無顯著影響，主成分皆為S-(+)-Linalool，其中，利用60oC烘乾葉子的效率最佳，乾燥所需時間最少（2 h），且只需使用少量電能（0.3 kWh）。至於乾燥葉子裝袋貯藏於室內環境6個月後仍保有大量的S-(+)-Linalool（21.1 - 28.4 mg/g leaf）；此外，葉碎片及葉粉放置於室溫環境60 min後，釋出之S-(+)-Linalool仍保有能舒緩人體壓力之濃度（9.8 mg m-3 g-1）。由上述葉子乾燥與貯藏試驗結果及葉子釋出至空氣中S-(+)-Linalool濃度分析結果得知，葉子精油及S-(+)-Linalool的安定性極佳，葉子磨碎後於一定時間內還可持續釋出對人體健康有益之S-(+)-Linalool。 綜合本研究結果得知，嫁接繁殖的伽羅木醇型土肉桂植株葉子之精油及S-(+)-Linalool含量高且安定性極佳，葉子磨碎後還會釋出大量S-(+)-Linalool。此外，伽羅木醇型土肉桂葉子具有使用便利、低成本、安定性佳及可永續利用的優點，未來不僅可以作為日常隨手可得的芳香材料，亦極具潛力作為開發紓壓產品之來源。

Cinnamomum osmophloeum ct. linalool is one chemotype of the indigenous cinnamon in Taiwan. Its leaf essential oil (LEO) and major component, S-(+)-linalool, both possess excellent anxiolytic activity. The aim of this study was to evaluate feasibility of leaf from Cinnamomum osmophloeum ct. linalool for aromatic materials. An advanced microextraction method: ultrasound-assisted microextraction (UAME) was established to extract the LEO. Then, the effects of physiological variations of the plant on chemical composition of the LEO as well as the stability of both LEO and S-(+)-linalool in the leaf were investigated. The results obtained from the optimal conditions of LEO extraction showed that the optimal condition for hydrodistillation (HD) was: 10 g leaf was hydrodistilled with diethyl ether addition in Clevenger apparatus for 30 min, while that for UAME was: 10 mg leaf was extracted using n-hexane in an ultrasonicator with the power of 80 W for 1 min. S-(+)-Linalool content obtained by UAME (28.3 ± 0.5 mg/g leaf) was comparable with that extracted by HD (26.9 ± 2.7 mg/g leaf), suggesting that UAME is a rapid method for analyzing the S-(+)-linalool content of C. osmophloeum ct. linalool leaves. To understand how physiological variations in C. osmophloeum ct. linalool affected chemical composition and S-(+)-linalool content of the LEO, four parameters including plant propagation methods (cuttage, grafting, seeding, and tissue culture), individual variation (6 grafting plants), seasonal variation (spring, summer, fall, and winter), and leaves at different stages of maturity (young, semi-mature, and mature) were explored by using both HD and UAME. Results indicated that yields of the LEOs and S-(+)-linalool content in cutting and grafting plants were higher than those obtained from seeding and tissue culture plants. Moreover, it was found that individual variation in six grafting plants did not significantly affect the chemical composition and S-(+)-linalool content in the LEOs. The observed seasonal variation in S-(+)-linalool content in the leaf was minimal. LEOs obtained in four seasons all had a high yield (≥ 2.9%) and a large quantity of S-(+)-linalool (≥ 27.0 mg/g leaf). In addition, results revealed that only mature leaf contained a large amount of S-(+)-linalool, compared with young and semi-mature leaf. These showed that mature leaf of grafting C. osmophloeum ct. linalool could be harvested all year round, being the excellent source of S-(+)-linalool. In addition, results obtained from the stability evaluation demonstrated that both air drying at ambient temperature and oven drying (30, 45, and 60oC) had no significant effect on the chemical composition of the LEO and S-(+)-linalool content. The major component in each LEO was S-(+)-linalool (≥ 78.6%). Oven-dried leaves at 60oC required 2 h and 0.3 kWh only, revealing it is the most efficient drying treatment. The result also showed that dried leaves packaged in polyethylene bag retained a large amount of S-(+)-linalool (21.1 - 28.4 mg/g) during 6-month storage at ambient temperature. After being crushed, within 60 min both leaf flakes and leaf powders emitted S-(+)-linalool in a concentration higher than 9.8 mg m-3 g-1 (a known concentration for the stress-relieving activity). These results showed that both the LEO and its major component, S-(+)-linalool, had an excellent stability in the C. osmophloeum ct. linalool leaf. Moreover, S-(+)-linalool, which was benefit to human health, could be emitted continuously from crushed leaf within a certain period of time. In summary, leaf of grafted C. osmophloeum ct. linalool possesses high LEO yield and S-(+)-linalool content with great stability throughout a year. Besides, the crushed leaf emitted a large amount of S-(+)-linalool into the air. Moreover, C. osmophloeum ct. linalool leaves have various advantages, including convenience, lower cost, great stability, and sustainable use. These results suggested that crushed leaf could be developed as a potential source of stress-relieving products and aromatic materials in daily life.