大葉楠類黃酮成分之研究

Abstract

在本研究中，一開始依據活性測試結果為導向之分離 (bioassay-guided separation)，尋找對甲型葡萄糖水解酶(α-glucosidase)有抑制作用的化合物。選定樟科楨楠屬植物大葉楠Machilus japonica Sieb. ＆ Zucc. var. kusanoi (Hayata) Liao (Lauraceae)葉部為研究目標，首先將酒精萃取物，經極性劃分為二氯甲烷、乙酸乙酯、正丁醇和水可溶四部分，並針對正丁醇可溶部分進行研究。但發現活性部分不強且成分散置，因此以一般方法進行正丁醇可溶部分之成分研究，經分離得到八個屬於類黃酮成分的化合物：2'-O-α-L-Rhamnopyranosyl isovitexin (1)，2'-O-α-L-Rhamnopyranosyl vitexin (2)，Apigenin 4'-O-β-D-glucopyranoside (3)，化合物4，化合物5，化合物6，Quercetin-3-O-β-D-galactoside (7)和Quercetin-3-O-β-D-glucoside (8)。其中化合物1到6屬於黃酮 (flavones)，而化合物7和8則屬於黃酮醇 (flavonols)，化合物4、5、6則為新架構天然物。 這一系列化合物對α-glucosidase的抑制效果並不理想，前六個化合物中，僅化合物3、5、6在100 μg/mL呈現強弱不一的抑制活性，抑制百分比依序為64.7%、18.7%及93.7%，然而在10 μg/mL濃度時皆無活性。

Guided by bioassay against α-glucosidase, the active constituents of the leaves extract of Machilus japonica Sieb. ＆ Zucc. var. kusanoi (Hayata) Liao (Lauraceae) were investigated in this study. Several attempts were made to concentrate the active fractions from this approach. However, it was found that the activity was not strong in each fraction. Then, the aim of this study turned to the separation of chemical constituents of the polar fractions via various chromatographic techniques. The effects led to the identification of eight compounds, 2'-O-α-L-rhamnopyranosyl isovitexin (1), 2'-O-α-L-rhamnopyranosyl vitexin (2), apigenin 4'-O-β-D-glucopyranoside (3), compound (4), compound (5), compound (6), quercetin-3-O-β-D-galactoside (7) and quercetin-3-O-β-D-glucoside (8). Compounds 1-6 belong to flavones and compounds 7-8 belong to flavonols. In addition, compounds 4-6 are disclosed to be new natural products, possessing a novel skeleton. These compounds exhibit weak inhibitory activity against α-glucosidase. Of these compounds tested (1-6), compounds 3, 5 and 6 exhibit 64.7 %, 18.7 % and 93.7 % of inhibitory activity, respectively, at a concentration level of 100 μg/mL; but no activity was obsevered for each compound at 10 μg/mL level.