探討黃耆中抑制腺苷脫氨酶活性之成份

腺苷脫氨酶(Adenosine deaminase, ADA)為嘌呤代謝的重要酵素，會將腺苷(adenosine)進行脫氨作用成為肌苷(inosine)。ADA廣泛存在生物體中，具有調節免疫作用，當免疫系統或發炎相關疾病發生時，大多與ADA不正常有關，同時，ADA的脫氨作用會使得某些抗癌或抗病毒藥物被代謝而失去活性，因此，藉由抑制劑來調節ADA活性，可讓此類藥物更有效率的被應用。黃耆(Radix Astragali)為膜莢黃耆(Astragalus membranaceus (Fisch.) Bunge)或蒙古黃耆(A. mongholicus Bunge)的乾燥根，被列為上品藥材、譽為諸藥補氣之最，黃耆有許多生理功效，如免疫調節、心血管保護、肝臟保護等。先前研究發現，黃耆中具有抑制ADA活性之成分，因此，本研究目的為進一步探討黃耆中具有抑制ADA酵素活性之各種成份。實驗以不同溶劑(水、乙醇、乙酸乙酯、正己烷)萃取黃耆，萃取率以水組最高為29.2%，其次為乙醇組萃取率為7.28%。但是，比較各溶劑萃取物對ADA酵素之抑制活性，乙醇萃取物顯示最佳的抑制效果，IC50約為0.16 mg/mL，其次為乙酸乙酯、正己烷，而水萃物效果最差，故選擇乙醇萃取物進行後續分離。將萃取物以水-乙酸乙酯做液-液分離，發現以乙酸乙酯層的效果較佳。進一步將乙酸乙酯層使用Diaion HP-20分離，酵素試驗結果顯示E和F區分最為有效。透過HPLC分析，顯示此二區分的主要成份為ononin、calycosin、formononetin，其中又以calycosin呈現較佳的抑制活性，但抑制效果比乙醇萃取物低。因此可以推論，黃耆的類黃酮成份具有ADA抑制效果，但抑制ADA效果來源並非單一化合物，應為不同成份間的加乘作用。

關鍵字

黃耆；腺苷脫氨酶；活性抑制；成分鑑定

並列摘要

Adenosine deaminase (ADA, EC 3.5.4.4) is an enzyme of the purine metabolism. It catalyzes the deamination of adenosine to inosine. This enzyme presents in various organisms like microorganisms, plants and animals and can regulate and maintain the function of immune system. ADA abnormalities are related to immune system and inflammation diseases. On the other hand, some drugs with anticancer and antivirus activities can be deaminated by ADA and lose the drug activities. Some reports revealed that ADA inhibitors can be used to treat these diseases and prevent the drugs from deamination. Radix Astragali is the root of Astragalus membranaceus (Fisch.) Bunge and A. mongholicus Bunge. It is used as a traditional medicine in China for thousands years. Radix Astragali has cardioprotective, immunomodulatory and antitumor activities. Previous research conducted in our lab has found that Radix Astragali possesses ADA inhibition activity. The objective of this research was to investigate the components of Radix Astragali that can inhibit the ADA activity. We extracted Radix Astragali by different solvents, including distilled water, ethanol, ethyl acetate and hexane. The highest extraction rate was 29.2 % of water extract, followed by 7.3 % of ethanol extract. In ADA inhibition test, the ethanol extract showed the highest inhibition activity (IC50 = 0.16 mg/mL), followed by ethyl acetate extract, hexane extract. Water extract had the lowest inhibition activity. The ethanol extract was further purified by liquid-liquid separation using water/ethyl acetate (EA) system. Then, the EA layer was separated by Diaion HP-20 resin. It was found that fraction E and F showed relatively higher enzyme inhibition activity, therefore, they were analyzed by HPLC. We found that ononin, calycosin and formononetin are the main components of these two fractions. Although calycosin showed the a better inhibition activity among these three components, its inhibition activity was still lower than that of the ethanol extract of Radix Astragali. According to the results, we can deduce that ADA inhibition activity of Radix Astragali is not from any single component. Several components may work synergistically that make ethanol extract of Radix Astragali possesses potent ADA inhibition activity.

並列關鍵字

adenosine deaminase ； Radix Astragali ； inhibition activity ； separation and identification

參考文獻

林郁進、張永勳、蔡新聲。1995。黃耆類藥材之鑑定研究 I.膜莢黃耆、蒙古黃耆與多序岩黃耆之辨偽。中華農業研究。44：101-113。

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探討黃耆中抑制腺苷脫氨酶活性之成份

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