Pyrroles As Antioxidants: Solvent Effects and the Nature of the Attacking Radical on Antioxidant Activities and Mechanisms of Pyrroles, Dipyrrinones, and Bile Pigments
作者:Patricia D. MacLean、Erin E. Chapman、Sarah L. Dobrowolski、Alison Thompson、L. Ross C. Barclay
DOI:10.1021/jo8005073
日期:2008.9.1
explained by hydrogen atom transfer, HAT, from the N-H of pyrroles to ROO(*) radicals. The k(inh) values in styrene of dimethyl esters of the bile pigments of bilirubin ester (BRDE), of biliverdin ester (BVDE), and of a model compound (dipyrrinone, 1) gave k(inh) in the order pentamethylhydroxychroman (PMHC) >> BRDE > 1 > BVDE. These antioxidant activities for BVDE and the model compound, 1, and PMHC
吡咯,2-甲基-3-乙基羧基-4,5-二-对-甲氧基苯基吡咯,6,2,3,4,5-四苯基吡咯,7的绝对速率常数k(inh)和化学计量系数n和2,3,4,5-四-对甲氧基苯基吡咯8与酚类抗氧化剂二叔丁基羟基茴香醚DBHA相比,在30摄氏度下由AIBN引发的异丙基苯的抑制氧化过程中具有相对的抗氧化活性( k(inh))DBHA> 8> 7> 6且n = 2,而在苯乙烯中,8> DBHA。这些结果可以通过氢原子从吡咯的NH转移到ROO(*)自由基来解释。苯乙烯中胆红素酯(BRDE)胆汁颜料的二甲基酯,联肝素酯(BVDE)和模型化合物(dipyrrinone,1)在二甲基酯中的k(inh)值以五甲基羟基苯并二氢吡喃(PMHC)的顺序给出k(inh) )>> BRDE> 1> BVDE。在甲醇存在下,由于吡咯NH基团上的氢键,BVDE和模型化合物1,以及PMHC的这些抗氧化剂活性急剧下降。相反,在甲