| 摘要: | 黃酮類為天然物中的一大類別，是植物特有之二次代謝產物。它不僅廣泛存在藥用植物中也存在於許多開花植物與食用植物中(例如：稻米、大豆、綠茶等)，因此黃酮類相較其他天然物的類別是與我們生活關係更緊密的。除此之外，黃酮類化合物還具有多樣的生物活性，例如:抗癌、抗發炎、抗氧化、保肝、抗菌等。在自然界中，黃酮類常有許多不同的取代基形成多樣的化學結構，因此透過黃酮類化合物結構與其生物活性的研究，將有助於醫藥研究的發展。
目前已知的黃酮類化合物總數約為7000種，對比植物種類的數量，可知仍然存在有許多未知的黃酮類化合物。為了能更快速的探知植物中的黃酮類化合物並分析其結構，需要更快速、更方便的分析方法。在現有的分析儀器中核磁共振儀是最有效的鑑定儀器，但是在小量樣本與混和物的分析中核磁共振儀卻有瓶頸，質譜儀相對於核磁共振儀，無疑是更好的選擇。但是在現今利用質譜儀分析未知天然物的方法，卻受限於可用資料庫太少，特別是植物資料庫，因此，本研究目的為設計可用於質譜儀快速分析未知黃酮類化合物的方法，而且不需要龐大的資料庫支持質譜訊號比對。利用此設計的方式，我們以Medicage sativa L.為樣本鑑定出多種黃酮類化合物。本次研究所設計的方法，參考了in silico database與in silico fragmentation的方法，其概念不僅可以使用在黃酮類化合物的鑑定上，未來亦可以用於質譜儀鑑定其他類型天然物方法的設計。
Flavonoids are the largest family of plant secondary metabolites, and which are important for medicinal development due to their biological and physiological functions. Though there are many kinds of detectors and analytic methods, e.g. nuclear magnetic resonance (NMR), liquid chromatography-mass spectrometry (LC-MS), it is still a tough work to identify flavonoids from natural resources. The efficiency of the analytical tools are limited by the experience of analysts, the concentration of analytes, and the number of references. Recently, scientists used liquid chromatography coupled with high resolution mass spectrometry (LC/HR-MS), and developed data processing network to deduce chemical structures of secondary metabolites. HR-MS is an efficient analytical equipment due to small sample amount needed, high signal to noise ratio, capabilities of predicting molecular formula and constructing MS database. Although scientists could possibly identified the known compounds by MS database matching, however, in most cases the database are incapable of identifying most of the unknown compounds in plant. So far, most of MS database are built from human or animal-metabolites, while botanical metabolite libraries are still limited. These problems are also encountered in identification of flavonoids. With an attempt to overcome the above-mentioned problems, we developed a rapid and rational method for identifying flavonoids using HR-MS and tandem MS fragmentation analysis. In this process, we don’t use LC system to separate compounds from plant extracts preliminarily, and apply HR-MS directly to predict the chemical formula of flavonoids. Subsequently, the structures of flavonoids are approached by the fragment ions arisen from tandem MS. By using this method, the flavonoids of the alfalfa (Medicage sativa L.) extracts has been predicted and identified successfully. |
