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• 系統編號 RB8404-1353

• 計畫中文名稱紫草成份的光安定性及其分解途徑的探討

• 計畫英文名稱 Photostability Study and Degradation Pathway of Shikon.

• 主管機關行政院國家科學委員會 • 計畫編號 NSC82-0412-B038-019 • 執行機構台北醫學院藥學研究所 • 本期期間 8202 ~ 8301 • 報告頁數 0 頁 • 使用語言中文 • 研究人員陳朝洋 Chen, Chau-Yan • 中文關鍵字紫草；Alkannin/shikonin 對掌異構物；光劣化；光安定性 • 英文關鍵字 Shikon；Alkannin/shikonin enantiomer；Photodegradation；Photostability • 中文摘要

自 Macrotomia euchroma (Royle) Pauls「軟紫草」可分離純化出含約 83/17 比例的 Alkannin((-)-5,8-dihydroxy-2-(1-hydroxy-4-methyl-3-pentenyl)- 1,4-naphthoquinone)及

Shikonin((+)-5,8-dihydroxy-2-(1-hydroxy-4-methyl-3-pentenyl)- 1,4-naphthoquinone)混合物。此 Naphthoquinone 類成分為對光敏感的化合物。Alkannin/shikonin 在氯仿溶液主要進行光氧化機序而產生

(-)-5,8-dihydroxy-2-(1-oxo-3-hydroxy-4-methyl-4-pentenyl)- 1,4-naphthoquinone。Alkannin/shikonin 的安定性高效液相層析法已被建立且應用在一些因子如溶媒,氧氣,容器種類,酸鹼質,緩衝溶液濃度,離子強度及溫度對光安定性的影響光解動力學研究上。光對 Alkannin/shikonin 安定性影響比溫度顯著,Alkannin/shikonin 的光解乃依一次動力學降解。Alkannin/shikonin 在溶媒中的光反應速率次序為氯仿>異丙醇>乙醇>甲醇。在乙醇中光反應速率會隨水比例的增加而增加。此外,褐色容器有效抑制 Alkannin/shikonin 的分解。容器中充氮氣亦能有意義地抑制 Alkannin/shikonin 的分解。Alkannin/shikonin 於未解離型(pH<6) 較解離型安定,於 pH=5 時,Alkannin/shikonin 的光反應速率不受緩衝溶液濃度及離子強度的影響。

• 英文摘要

A mixture of alkannin ((-)-5,8-dihydroxy-2-(1-hydroxy-4-methyl-3-pentenyl)-1,4-naphthoquinone) and shikonin

((+)-5,8-dihydroxy-2-(1-hydroxy-4-methyl-3-pentenyl)-1,4-naphthoquinone), isolated from Macrotomia euchroma (Royle) Pauls, "Nanshikon", is sensitive to light exposure. The alkannin/shikonin in chloroform solution undergoes photo-oxidation process to mainly form a naphthoquinone (-)-5,8-dihydroxy-2-(1-oxo-3-hydroxy-4-methyl-4-pentenyl)-1,4-naphthoquinone. A

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stability-indicating HPLC assay method was established and used to examine the photodegradation kinetics. The photodegradation kinetics were studies as function of solvent, container species, pH, buffer concentration, ionic strength, and temperature. The light effect on stability of alkannin/shikonin is more significant than temperature. The photodegradation of alkannin/shikonin follows first order kinetics. The rate of photodegradation is in the order of chloroform>isopropanol>ethanol>methanol. The rate of

photodegradation increases with increasing the proportion of water in ethanol. The amber container is effective to inhibit the disappearing rate of alkannin/shikonin. The rate of photodegradation decreases significantly with filling of nitrogen gas. The unionized alkannin/shikonin is more stable than ionized form (pH>6). At pH5, there was no influence of buffer concentration and ionic strength on the rate of photodegradation.