| 摘要: | 桑（Morus alba L.）始載於神農本草經，其用部有桑枝、桑白皮、桑葉、桑椹。現代藥理的研究指出桑的四種藥用部位多具有抗氧化、降血糖、抗發炎及降血脂之作用，而在成分之研究上則發現主要含有多酚類、黃酮類及香豆素類等化合物。因此，本研究針對桑四個藥用部位之甲醇抽提物進行抗氧化活性及對乙醯膽鹼酯酶、單胺氧化酶的抑制活性之分析比較，之後再探討其香豆素類成分 scopoletin對 scopolamine 誘發大鼠記憶障礙之影響，及其改善作用機制。
結果發現在桑的四個藥用部位中總多酚類含量以桑枝最多，黃酮類含量則以桑葉較多。其次，在抗氧化活性上，桑枝有較佳之總抗氧化活性；桑葉則具較佳之DPPH 自由基清除能力及還原能力。至於在特定自由基的清除能力上，桑枝有較佳的氫氧自由基清除能力，桑葉則對超氧陰離子及過氧化氫有較佳的清除能力。另在乙醯膽鹼酯酶抑制活性上，桑枝、桑葉、桑椹皆有不錯的抑制活性；在單胺氧化酶的抑制活性上，則以桑枝具有較佳的 MAO-A 及 MAO-B 的抑制活性。
最後，scopoletin 於 0.03、0.1 mg/kg 劑量下，對 scopolamine 誘導大鼠在水迷宮以及十字迷宮學習操作障礙之現象均具有改善作用影響，此作用應與降低大鼠腦內皮質區乙醯膽鹼酯酶及單胺氧化酶活性，增加皮質區內 NE 及 DA 濃度有關。
綜合以上所述，桑之藥用部位以桑枝與桑葉具有較高的抗氧化活性、 ROS 自由基清除能力及酶的抑制活性。此作用與其含有較多之多酚類、黃酮類及香豆素類成分有關。而桑之成分 scopoletin 具改善scopolamine 誘導大鼠記憶障礙作用，其機轉與降低大鼠腦內皮質區乙醯膽鹼酯酶及單胺氧化酶活性，增加皮質區內 NE 及 DA 濃度有關。因此，在桑之藥用部位中，以桑枝及桑葉較具有開發為記憶障礙治療藥物之潛力。
The branch, cortex, leaf and fruit of Morus alba L. (Moraceae) are used for medicinal herbs, which were described in Shen – Nung – Pen - Ts’ao - Ching. Modern pharmacology indicated these four parts have antioxidant, antidiabetic, antiinflammatory and antihyperlipidemic activities. The phytochemical compositions of these four parts included polyphenols, flavonoids and coumarins. Therefore, the aim of this research is to compare the antioxidant, acetylcholinesterase-inhibiting and monoamine oxidase -inhibiting activities of these four parts of Morus alba. In addition, I also explored the mechanism of the ameliorating effects of scopoletin on the scopolamine induced memory impairment in rats.
First, the results showed that the branch had the highest phenolic content, and the leaf had the highest flavonoid content among four parts of Morus alba. Then, the branch had better scavenging ABTS radical and hydroxyl radical scavenging activity than the other parts of Morus alba. The leaf had better scavenging DPPH, reducing power, superoxide anion and H2O2 radical than other parts of Morus alba. On the other hand, the branch, leaf and fruit had better acetylcholinesterase-inhibiting effects, and the branch had the best MAO-A and MAO-B inhibiting activities.
Finally, scopoletin ameliorated the scopolamine induced memory impairment on water maze and elevated plus maze in rats. Scopoletin selectively inhibited the activity of acetylcholinesterase and monoamine oxidase, and increased the NE and DA concentrations in cortex.
In conclusion, the branch and leaf had the better antioxidant, ROS scavenging and enzyme inhibiting activities among four parts of Morus alba L.. Scopoletin ameliorated the scopolamine induced on water maze and elevated plus maze in rats. The mechanism of the ameliorating effects of scopoletin was related to the increase on the NE and DA concentrations in cortex by selectively inhibiting the activity of acetylcholinesterase and monoamine oxidase. Therefore, the branch and leaf of Morus alba L. were potential medicinal parts of Morus alba L. for the treatment of memory impairment. |
