活性跟踪法研究地骨皮中抑制NF-κB的化学成分

Bioassay-guided fractionation of constituents targeting mediators of inflammation from Lycii Cortex as inhibitors of NF-κB

传统中药地骨皮常用于治疗许多与炎症相关的疾病。该研究目的是确定地骨皮中抑制核转录因子NF-κB(炎症关键调控子)的活性成分。对不同溶剂的地骨皮提取物进行体外抑制NF-κB的活性试验,结果发现乙酸乙酯提取物与甲醇提取物表现出较强的抑制活性。通过活性跟踪分离纯化,获得4种酚酰胺类化合物,分别为:反-对羟基肉桂酰酪胺(1)、反-阿魏酰酪胺(2)、反-咖啡酰酪胺(3)与二氢咖啡酰酪胺(4)。它们对肿瘤坏死因子(TNF-α)诱导的NF-κB活性的抑制率差异非常显著,抑制率大小为3>4>2≈1。推测反-咖啡酰酪胺为关键活性成分,其IC_(50)为18.41μmol·L^(-1)。通过构效关系分析说明,反-咖啡酰酪胺C-3位的羟基可能是与NF-κB结合的高亲合位点,而且C-7,8位双键介导了苯环、羰基的π电子共轭作用,从而形成独特的平面空间构型,有助于抗炎分子与靶标蛋白的空间契合。由此推断,含有α,β-不饱和酮及苯环的迈克尔受体结构与邻二酚羟基共同决定了化合物3的生物活性。

Lycii Cortex, a popular herb medicine in traditional Chinese medicine, is used to treat different inflammation-related diseases. The aim of our work is to find the key constituents inhibiting NF-KB, a key regulator of inflammation. In the investigations of cell-based in vitro assays of extracts, we found that both ethyl acetate extract and methanol extract of Lycii Cortex inhibited the TNF- a-induced activation of NF-KB. Through bioassay-guided fractionation, we identified 4 phenolic amides including trans-N-（p-coumaroyl） tyramine （ 1 ）, trans -N-feruloyltyramine （ 2 ）, trans -N-caffeoyhyramine （3）, and dihydro-N-caffeoyltyramine （ 4 ）. Four phenolic amides showed differently inhibitory activities on TNF-a -induced NF-KB activation. Trans-N-caffeoyhyramine（3） was identified as the key component with an IC50 of 18.41 umol . L-1. It was suggested that the hydroxyl group at C-3 in trans-N-caffeoyltyramine might be a key binding site and its C-7,8-double bond might play an important role on NF-KB inhibitory activities as the link of the conjugation of π electrons leading to a partial planar conformation. It might be inferred that the biological activity of compound 3 is attributed to the structure of Michael reaction acceptor containing a, β-unsaturated ketones and benzene along with hydroxyl group in o-diphenol.