Apparent Intramolecular Acyl Migration and Hydrolysis of Furosemide Glucuronide in Aqueous Solution.
作者:Hitoshi SEKIKAWA、Naomi YAGI、Emil T. LIN、Leslie Z. BENET
DOI:10.1248/bpb.18.134
日期:——
The stability of furosemide glucuronide (FG) was investigated in buffer solutions ranging from pH 1 through 10. This glucuronic acid conjugate was the major metabolite of furosemide (F) excreted in human urine. FG, obtained by extraction from human urine, was purified by ion-exchange chromatography. The concentration of FG, acyl migration isomers of FG (FG-iso), and F were determined simultaneously with an HPLC method that included fluorescence detection and gradient elution. FG was found to be unstable in highly acidic and in neutral to alkaline solutions. Hydrogen ion and hydroxy ion catalyzed the hydrolysis of FG below pH 2.8 and above pH 5.6, respectively. Above pH 3.7, FG instability led to the formation of eight FG-iso compounds. Though β-glucuronidase cleaved FG, the FG-iso compounds were resistant to the enzyme. The half-life of FG in a buffer solution at pH 7.4 and 37°C was 4.4 h. The maximum stability of FG (half-life about 62 d) occurred at approximately pH 3.2. Below pH 3.7, acyl migration products of FG were not detected. Instead, the hydrolysis of FG to F and glucuronic acid was followed by the formation of 4-chloro-5-sulfamoylanthranilic acid (CSA), a secondary product in acidic media.
研究了呋塞米葡萄糖醛酸苷(FG)在 pH 值为 1 到 10 的缓冲溶液中的稳定性。这种葡萄糖醛酸共轭物是人体尿液中排出的呋塞米(F)的主要代谢物。从人体尿液中提取的 FG 经离子交换色谱法纯化。采用包括荧光检测和梯度洗脱的高效液相色谱法同时测定了 FG、FG 的酰基迁移异构体(FG-iso)和 F 的浓度。发现 FG 在高酸性和中性至碱性溶液中不稳定。氢离子和羟基离子分别在 pH 值低于 2.8 和高于 5.6 时催化 FG 的水解。当 pH 值高于 3.7 时,FG 的不稳定性会导致形成八种 FG-iso 化合物。虽然 β-葡糖醛酸酶能裂解 FG,但 FG-iso 化合物对该酶具有抗性。FG 在 pH 值为 7.4、温度为 37°C 的缓冲溶液中的半衰期为 4.4 小时。pH 值低于 3.7 时,检测不到 FG 的酰基迁移产物。相反,FG 在水解成 F 和葡萄糖醛酸后,会形成 4-氯-5-磺酰胺基兰基苯甲酸(CSA),这是酸性介质中的一种次级产物。