Iwahashi H, Ikeda A, Negoro Y, Kido R
Biochem J. 1986 Jun 1;236(2):509-14. doi: 10.1042/bj2360509.
E.p.r. signals were detected in an all-trans-retinoic acid/haematin incubation mixture by using an e.p.r. spin-trapping technique. The spin adducts are presumably attributable to some intermediates in haematin-catalysed retinoic acid 5,6-epoxidation, since addition of nitrosobenzene to the reaction mixture dose-dependently inhibited the epoxidation. Analysing the reaction mixture by h.p.l.c.-e.p.r. spectrometry resulted in the detection of three peaks (III-1, III-2, IV) ascribable to the radical species. Two (peaks III-1 and -2) of the three peaks, which appeared 10 min after the reaction had started, seem to be attributable to the radical species directly participating in the epoxidation. The radicals trapped by nitrosobenzene do not appear to be derived from active oxygen, since none of these peaks were detected in a similar h.p.l.c. analysis of O2- and OH.-generating systems. They are presumably derived from retinoic acid. This view is also supported by the following results: none of these peaks were detected in the h.p.l.c. elution profile of the reaction mixture when retinoic acid was absent; peaks III-1 and 2 were detected even under anaerobic conditions, and their peak heights were unchanged under aerobic conditions.
采用电子顺磁共振（E.p.r.）自旋捕获技术，在全反式维甲酸/血红素孵育混合物中检测到了E.p.r.信号。自旋加合物可能归因于血红素催化的维甲酸5,6 - 环氧化反应中的某些中间体，因为向反应混合物中添加亚硝基苯会剂量依赖性地抑制环氧化反应。通过高效液相色谱 - 电子顺磁共振（h.p.l.c.-e.p.r.）光谱分析反应混合物，检测到了三个可归因于自由基物种的峰（III - 1、III - 2、IV）。反应开始10分钟后出现的三个峰中的两个（峰III - 1和III - 2）似乎归因于直接参与环氧化反应的自由基物种。被亚硝基苯捕获的自由基似乎并非源自活性氧，因为在对产生O2-和OH-的体系进行类似的高效液相色谱分析中未检测到这些峰中的任何一个。它们可能源自维甲酸。以下结果也支持这一观点：当不存在维甲酸时，在反应混合物的高效液相色谱洗脱图谱中未检测到这些峰中的任何一个；即使在厌氧条件下也检测到了峰III - 1和2，并且它们的峰高在有氧条件下保持不变。
