Dage J L, Ackermann B L, Barbuch R J, Bernotas R C, Ohlweiler D F, Haegele K D, Thomas C E
Hoechst Marion Roussel, Inc., Cincinnati, OH USA.
Free Radic Biol Med. 1997;22(5):807-12. doi: 10.1016/s0891-5849(96)00425-x.
3,4-Dihydro-3,3-dimethyl-isoquinoline-2-oxide (MDL 101,002) is a conformationally constrained cyclic analog of the known spin trap alpha-phenyl N-tert-butyl nitrone (PBN). Because of PBN's ability to scavenge free radicals, MDL 101,002 is currently being evaluated in stroke models as a means to ameliorate the oxidative insult associated with reperfusion injury. To augment our understanding of the radical scavenging mechanism of this potential drug, MDL 101,002 was incubated with soybean lipoxygenase in the presence of linoleic acid to study the interaction between MDL 101,002 and free radicals formed during lipid peroxidation. Analysis of the reaction mixture was performed by high performance liquid chromatography using normal phase conditions with detection by atmospheric pressure chemical ionization mass spectrometry (APCI-MS). Similar to the work by Iwahashi et al. [Arch. Biochem. Biophys., 1991, 285, 172], who studied the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butyl nitrone (4-POBN), an adduct that suggested the trapping of pentyl radicals by MDL 101,002 was observed. However, the apparent molecular ion for this adduct (246 Da) was 1 Da lower than would be predicted if a pentyl radical had simply added to MDL 101,002. In addition, the adduct exhibited significant absorbance at 304 nm, consistent with the unsaturated nitrone structure of MDL 101,002. To account for these observations, it is postulated that, after the initial capture of a pentyl radical, subsequent abstraction of a hydrogen atom by a neighboring radical occurs to regenerate a nitrone (1-pentyl analog of MDL 101,002). We present evidence for this adduct and offer a mechanism for its formation. These findings indicate that mass spectroscopic analysis of stable nitrone radical adducts may be useful in the identification of radical-dependent damage in vivo and possibly in clinical development of MDL 101,002 as an antioxidant pharmaceutical.
3,4-二氢-3,3-二甲基异喹啉-2-氧化物（MDL 101,002）是已知自旋捕获剂α-苯基N-叔丁基硝酮（PBN）的构象受限环状类似物。由于PBN具有清除自由基的能力，目前正在中风模型中评估MDL 101,002，作为减轻与再灌注损伤相关的氧化损伤的一种手段。为了加深我们对这种潜在药物自由基清除机制的理解，在亚油酸存在的情况下，将MDL 101,002与大豆脂氧合酶一起孵育，以研究MDL 101,002与脂质过氧化过程中形成的自由基之间的相互作用。反应混合物的分析通过高效液相色谱法进行，采用正相条件，通过大气压化学电离质谱（APCI-MS）检测。与Iwahashi等人[《生物化学与生物物理学报》，1991年，285卷，172页]的工作类似，他们研究了自旋捕获剂α-(4-吡啶基-1-氧化物)-N-叔丁基硝酮（4-POBN），观察到一种加合物，表明MDL 101,002捕获了戊基自由基。然而，该加合物的表观分子离子（246 Da）比戊基自由基简单加成到MDL 101,002上所预测的低1 Da。此外，该加合物在304 nm处表现出显著的吸光度，与MDL 101,002的不饱和硝酮结构一致。为了解释这些观察结果，推测在最初捕获戊基自由基后，相邻自由基随后夺取一个氢原子以再生硝酮（MDL 101,002的1-戊基类似物）。我们提供了该加合物的证据并提出了其形成机制。这些发现表明，稳定硝酮自由基加合物的质谱分析可能有助于体内自由基依赖性损伤的鉴定，并且可能有助于MDL 101,002作为抗氧化药物的临床开发。
