- 期刊
龍膽萃取之脂質氧合酶抑制與抗發炎性
Lipoxygenase Inhibition and Anti-Inflammatory Effect of Gentianae Scabrae Radix Extract
摘要
本研究以體外脂質氧合酶抑制法(In-vitro 5-Lipoxygenase Inhibition Assay)結合酵素動力學(enzyme kinetics)的系統，探討龍膽(Gentianae scabrae Radix)超音波水萃物之抗炎活性。龍膽的萃取濃縮率為3%，研究發現龍膽萃取物對脂質氧合酶(5-LOX)的抑制率(IC_(50) = 0.0320 mg/mL)與去甲二氫癒創木酸(Nordihydroguaiaretic acid, NDGA)、沒藥醇(Bisabolol)及尿囊素(Allantoin)的效果相近(IC_(50)= 0.0205~0.0302 mg/mL)，但略優於菸鹼醯胺(Nicotinamide)(IC_(50) = 0.0490 mg/mL)。動力學曲線顯示龍膽萃取物抑制5-LOX的活性，減少了亞麻油酸(Linoleic acid)的氫過氧化程度，呈現劑量依賴關係(Dose dependent)。另以Lineweaver-Burk雙倒數作圖求得龍膽萃取物存在下，linoleic acid與5-LOX酵素反應最高初速值(V_(max))由0.04 μmol/min大幅降低至0.00814 μmol/min，Michaelis-Menten常數(K_m)為0.024 mM大於原始的0.0184 mM。Km變大代表龍膽萃取物與 Linoleic acid 競爭活化位置。Linoleic acid需要更大的濃度才能達到1/2 V_(max)速率。V_(max)的下降代表龍膽萃取物可與自由的酵素或基質酵素複合物結合，基質的增加不能克服抑制劑的影響而使V_(max)下降。綜合動力學行為可知，龍膽萃取物的5-LOX抑制機轉屬於混合型(Mixed-type)。比較K_m高低次序為NDGA＞Bisabolol＞龍膽萃取物＞Nicotinamide＞Allantoin，再次證明龍膽萃取物優異的抗發炎活性。
並列摘要
Anti-inflammatory activity and 5-lipoxygenase inhibitory behavior of Gentianae scabrae Radix extracts have been evaluated by 5-lipoxygenase inhibition assay and enzyme kinetics method in our studies. Linoleic acid was used as substrate for 5-lipoxygenase assay. Results showed that Gentianae scabrae Radix extracts are able to decrease the appetence between linoleic acid and 5-lipoxygenase. The Michaelis-Menten constant K_m of Gentianae scabrae Radix extracts (0.024 mM) exceeds Nicotinamide(0.022 mM), Allantoin (0.019 mM) and the Km value without whitening inhibitor (0.0184 mM). The higher apparent K_m value of Gentianae scabrae Radix extract may indicate a stronger anti-inflammatory effect, which is consistent with the finding of the small half maximal inhibitory concentration (IC_(50) = 0.0320 mg/mL) of the extract. Further kinetic study suggested that Gentianae scabrae Radix extract behaved as a mixed-type inhibitor toward 5-lipoxygenase.