Primaquine is an important antimalarial agent because of its activity against exoerythrocytic forms of Plasmodium spp. Methemoglobinemia and hemolytic anemia, however, are dose-limiting side effects of primaquine therapy. These hemotoxic effects are believed to be mediated by metabolites, although the identity of the toxic specie(s) and the mechanism underlying hemotoxicity have remained unclear. Previous studies showed that an N -hydroxylated metabolite of primaquine, 6-methoxy-8-hydroxylaminoquinoline, was capable of mediating primaquine-induced hemotoxicity. The present studies were undertaken to investigate the hemolytic potential of 5-hydroxyprimaquine (5-HPQ), a phenolic metabolite that has been detected in experimental animals. 5-HPQ was synthesized, isolated by flash chromatography, and characterized by NMR spectroscopy and mass spectrometry. In vitro exposure of 51Cr-labeled erythrocytes to 5-HPQ induced a concentration-dependent decrease in erythrocyte survival (TC50 of ca. 40 μM) when the exposed cells were returned to the circulation of isologous rats. 5-HPQ also induced methemoglobin formation and depletion of glutathione (GSH) when incubated with suspensions of rat erythrocytes. Furthermore, when red cell GSH was depleted (>95%) by titration with diethyl maleate to mimic GSH instability in human glucose-6-phosphate dehydrogenase deficiency, a 5-fold enhancement of hemolytic activity was observed. These data indicate that 5-HPQ also has the requisite properties to contribute to the hemotoxicity of primaquine. The relative contribution of N -hydroxy versus phenolic metabolites to the overall hemotoxicity of primaquine remains to be assessed.
伯氨喹是一种重要的抗疟疾药物,因为它对疟原虫的外周血形式具有活性。然而,高
铁血红蛋白血症和溶血性贫血是
伯氨喹治疗的剂量限制性副作用。这些血液毒性效应被认为是由代谢产物介导的,尽管毒性物种和血液毒性机制的性质仍然不清楚。先前的研究表明,
伯氨喹的N-羟基代谢产物6-甲氧基-8-羟基
氨基
喹啉能够介导
伯氨喹诱导的血液毒性。本研究旨在调查5-羟基
伯氨喹(5-HPQ)的溶血潜力,这是一种在实验动物中检测到的
酚类代谢产物。5-HPQ通过快速色谱法合成、分离,并通过核磁共振波谱和质谱进行表征。当暴露的细胞返回同源大鼠的循环时,51Cr标记的红细胞在体外暴露于5-HPQ时,红细胞存活率呈浓度依赖性下降(TC50约为40μM)。当与大鼠红细胞悬浮液一起培养时,5-HPQ还会诱导高
铁血红蛋白的形成和
谷胱甘肽(GSH)的耗竭。此外,当用
马来酸二乙酯滴定红细胞GSH耗竭(>95%)以模拟人类
葡萄糖