柳杉樹皮抗細菌及抗氧化活性成分之研究

Abstract

本研究以柳杉（Cryptomeria japonica D. Don）樹皮的乙醇抽出物進行抗細菌和抗氧化的活性評估。柳杉樹皮乙醇抽出物和其各可溶部中，以正己烷可溶部之抗細菌活性最佳，最小抑制濃度值（Minimum inhibition concentration, MIC）為250 μg/mL，因此取此可溶部進一步地分離出有效成分，並於活性的次分離部中純化鑑定出9種化合物，包括7種雙類（Ferruginol、Isopimaric acid、Iguestol、Isopimarol、Phyllocladan-16α-ol、Sandaracopimarol和Sugiol）與2種固醇類（β-Sitosterol和β-Sitostenone），β-Sitostenone為首次自柳杉中分離出的化合物。其中6種化合物具有抗細菌活性，活性依序為：Ferruginol > Isopimaric acid > Sugiol > Sandaracopimarinol > Iguestol > Isopimarol。以Ferruginol具有最佳的抗細菌活性，對所有的試驗菌種之MIC範圍為6.3-12.5 μg/mL，其次為Isopimaric acid對糞腸球菌（Enterococcus faecalis）與金黃色葡萄球菌（Staphylococcus aureus）的MIC值為15.6 μg/mL，皆具有良好的抗細菌活性。 在抗氧化活性評估方面，試驗結果顯示，柳杉樹皮抽出物的乙酸乙酯可溶部之總酚類含量（789.7 mg of GAE/g）、總黃酮類含量（35.8 mg of RE/g）與原花青素含量（464.1 mg of CAE/g）皆最高。此外，乙酸乙酯可溶部具有最好的DPPH捕捉能力（IC50 = 4.4 µg/mL）、總抗氧化能力（2.87 mM of Trolox）及還原能力，而抑制β-胡蘿蔔素脫色的能力亦最佳；續以層析方法對乙酸乙酯可溶部進行分離，從活性次分離部中分離出(+)-Catechin和(–)-Epicatechin，此兩種化合物均具有良好的抗氧化活性。綜合上述結果顯示，柳杉樹皮的乙醇抽出物為良好的天然抗細菌與抗氧化物質來源，值得進一步地開發與利用，以提升柳杉樹皮的利用價值。

In this study, the ethanolic extract from the bark of Cryptomeria japonica D. Don was evaluated its antibacterial and antioxidant activities. Among ethanolic extract and its four fractions, n-hexane soluble fraction possessed the best antibacterial activity against four Gram-positive bacteria (Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis, and Methicillin-resistant Staphylococcus aureus, MRSA) with minimum inhibitory concentration (MIC) of 250 μg/mL. Nine compounds including seven diterpenoids (ferruginol, isopimaric acid, iguestol, isopimarol, phyllocladan-16α-ol, sandaracopimarol and sugiol) and two steroids (β-sitosterol and β-sitostenone) were isolated, and it is the first time that β-sitostenone was isolated from the C. japonica plant. Six compounds exhibited excellent antibacterial activities, their ability in decreasing order was as follows: ferruginol > isopimaric acid > sugiol > sandaracopimarinol > iguestol > isopimarol. Ferruginol possessed the strongest antibacterial activity within all the compounds and had MIC values ranging from 6.3 to 12.5 μg/mL against all bacteria tested. In addition, antioxidant activities of sugi bark extract and four fractions were also examined. According to the results, the fraction with the highest content of total phenolic contents (789.7 mg of GAE/g), total flavonoid contents (35.8 mg of RE/g) and proanthocyanidin contents (464.1 mg of CAE/g) was ethyl-acetate soluble fraction. Also, ethyl-acetate soluble fraction exhibited the best DPPH radical scavenging activity (IC50 = 4.4 µg/mL), TEAC value (2.87 mM of trolox), reducing power, and the ability to decrease color bleaching of β-carotene. (+)-Catechin and (–)-epicatechin were isolated and exhibited excellent antioxidant activities. Results showed that ethanolic extract of C. japonica bark is good at antibacterial and antioxidant activities and is worthy of further explorative utilization.