檸檬葉甲醇萃取物抗氧化性之研究

Studies on Antioxidative Activity of Methanol Extracts from Lemon (Citrus limon Burm.) Leaves

本文旨在研究檸檬葉甲醇萃取物之抗氧化特性，探討其於不同脂質過氧化系統中對脂質過氧化之抑制效果，並分析其所含有之主要抗氧化成分。結果顯示，以甲醇萃取檸檬葉比其它溶劑萃取者具有較高的萃取率，並以檸檬老齡葉之萃取率為最好，且所得檸檬葉萃取物的抗氧化活性最高，而冷凍乾燥檸檬葉甲醇萃取物（MEFDL）的抗氧化能力又比熱風乾燥者高。MEFDL對α，α-diphenyl-β-picrylhydrazyl自由基、超氧陰離子及過氧化氫之清除效果分別可達到63.1、67.9及75.6%，亦具有甚高之還原力與螯合銅離子之能力。在不同催化因子所催化之脂質過氧化系統中，則會表現出不同程度之抗氧化性，並以在自氧化系統中有最佳之抗氧化性，且在各系統中，較高濃度下均會表現出較佳之脂質過氧化抑制效果。由主要抗氧化成分分析得知，MEFDL含有抗壞血酸、α-tocopherol、β-carotene及總多酚類分別為0.93、0.8、1.69及2.8mg／g。 The objectives of this research were to investigate the antioxidative properties of methanol extracts from lemon leaves. The study items included antioxidation, antioxidative activity in different lipid peroxidation systems, and contents of antioxidants. Results showed that the extraction by methanol had higher than those by other solvents. Antioxidant capacity of methanol extracts of both freeze-dried and hot-dried elder age lemon leaves were higher than those in middle or young age. Compared with methanol extracts from hot air-dried lemon leaves (MEHDL), we found methanol extracts from freeze-dried lemon leaves (MEFDL) had better antioxidant activity. MEFDL had 63.1, 67.9, and 75.6% scavenging effect onα, α-diphenyl-β-picryhydrazyl(DPPH), superoxide anion, and hydrogen peroxide, respectively. MEFDL also showed high reducing power and chealting ability with Cu+2. MEFDL exhibited the highest antioxidative activity in autoxidation system than in other induced systems, and had higher inhibited peroxidation effects at higher dosage in any peroxidation systems. The primary antioxidant contents of ascorbic acid, α-tocopherol, β-carotene, and total phenol and in MEFDL were 0.93, 0.8, 1.69, and 2.8 mg/g, respectively.