作者:Gonçalo C. Justino、Margarida Rodrigues、M. Helena Florêncio、Lurdes Mira
DOI:10.1002/jms.1630
日期:2009.10
Hypobromous acid (HOBr) produced by both eosinophil peroxidase (EPO) and myeloperoxidase (MPO) is a stronger oxidant than HOCl, and is also essential for optimal and efficient microbial killing. Considering the potential cytotoxic effect of HOBr, if it is formed outside the phagosome, it should be useful to scavenge it in order to protect the nearby tissues. In this study the ability of selected flavonoids to protect against HOBr mediated oxidation reactions was performed through a competitive reaction, and the resulting products identified by high performance liquid chromatography (HPLC) and electrospray ionization tandem mass spectrometry(ESI-MS/MS). Several structural features were found to be important to confer high antioxidant activity to flavonoids towards HOBr: the C2C3 double bond and the 3OH group in the C-ring, and the presence of both 5OH and 7OH groups in the A-ring. The MS results showed that flavonoids are dibrominated in the A-ring, suggesting that (except for fisetin) bromination occurs at C6 and C8 positions, through an electrophilic aromatic substitution reaction. The chemical modifications achieved by bromination of flavonoids have changed their biological properties, presenting their brominated derivatives higher antioxidant activity, as radical scavengers, and higher lipophilicity, than the parent flavonoids. Brominated flavonoids may then diffuse easily through membranes increasing the intracellular concentration of the compounds. These locally formed metabolites may also interact with signaling cascades involving cytokines and regulatory transcription factors, thus playing a role in inflammation and in the regulation of immune response. Copyright © 2009 John Wiley & Sons, Ltd.
由嗜酸性粒细胞过氧化物酶(EPO)和髓过氧化物酶(MPO)产生的次溴酸(HOBr)是一种比次氯酸(HOCl)更强的氧化剂,并且对于最佳和高效的微生物杀灭至关重要。考虑到HOBr可能的细胞毒性效应,如果它在吞噬体外形成,则清除它可以保护附近的组织。在本研究中,选择的黄酮类化合物对抗HOBr介导的氧化反应的保护能力通过竞争反应进行研究,并通过高效液相色谱(HPLC)和电喷雾电离串联质谱(ESI-MS/MS)识别出所产生的产物。发现几个结构特征对赋予黄酮类化合物高抗氧化活性与HOBr相关非常重要:C2=C3双键和C环中的3-OH基团,以及A环中同时存在的5-OH和7-OH基团。质谱结果显示,黄酮类化合物在A环中被二溴化,表明(除了鬼针草素)溴化发生在C6和C8位点,通过电亲电芳香取代反应实现。黄酮类化合物的溴化所带来的化学修饰改变了它们的生物学特性,使得其溴化衍生物在作为自由基清除剂时表现出更高的抗氧化活性和更高的脂溶性,较之于母体黄酮。溴化黄酮可能更容易通过膜扩散,从而提高化合物的细胞内浓度。这些局部形成的代谢物也可能与涉及细胞因子和调节转录因子的信号传导级联反应相互作用,从而在炎症和免疫应答的调节中发挥作用。版权所有 © 2009 John Wiley & Sons, Ltd.