5-O-(4-[125I]Iodobenzyl)-L-ascorbic Acid: Electrophilic Radioiodination and Biodistribution in Mice
作者:Jintaek Kim、Tomohiro Kino、Hiroharu Kato、Fumihiko Yamamoto、Kohei Sano、Takahiro Mukai、Minoru Maeda
DOI:10.1248/cpb.60.235
日期:——
As a part of our efforts to develop potential imaging agents for ascorbate bioactivity, 5-O-(4-[125I]iodobenzyl)-L-ascorbic acid ([125I]1) was prepared through a two-step sequence which involved radioiodo-destannylation of a protected tributylstannyl precursor 6, followed by hydrolysis in acidic methanol of the protecting groups in 61% overall radiochemical yield, with a radiochemical purity of over 98% and a specific activity of more than 15.4 GBq/μmol. Tissue distribution of [125I]1 in tumor-bearing mice showed signs of distribution profiles similar to the reported results for 6-deoxy-6-[18F]fluoro-L-ascorbic (6-18FAsA) acid and 6-deoxy-6-[131I]iodo-L-ascorbic acid (6-131IAsA) but with notable differences in the adrenal glands, in which considerably lower uptake of radioactivity and rapid clearance with time were observed. Pretreatment of mice with a known inhibitor of ascorbate transport, sulfinpyrazone, did not produce any significant change in the adrenal uptake of radioactivity after injection of [125I]1 compared to the control, suggesting that uptake in the adrenal glands is independent of the sodium-dependent vitamin C transporter 2 transport mechanism. Introduction of a bulky substituent at C-5 on AsA, such as an iodobenzyloxy group, may not be suitable for the design of analogs that may still be able to maintain characteristic distribution properties in vivo seen with AsA itself.
作为我们开发抗坏血酸生物活性潜在成像剂工作的一部分,5-O-(4-[125I]碘苄基)-<小>L小>-抗坏血酸([125I]1)是通过两步法制备的、然后在酸性甲醇中水解保护基团,总放射化学收率为 61%,放射化学纯度超过 98%,比活度超过 15.4 GBq/μmol。4 GBq/μmol。[125I]1在肿瘤小鼠体内的组织分布显示出与6-脱氧-6-[18F]氟-<小>L小>-抗坏血酸(6-18FAsA)酸和6-脱氧-6-[131I]碘-<小>L小>-抗坏血酸(6-131IAsA)的报告结果相似的分布特征,但在肾上腺有显著差异,在肾上腺中观察到的放射性摄取和随时间的快速清除要低得多。与对照组相比,用已知的抗坏血酸转运抑制剂磺吡酮对小鼠进行预处理后,注射 [125I]1 后肾上腺对放射性的摄取没有任何明显变化,这表明肾上腺的摄取独立于钠依赖性维生素 C 转运体 2 的转运机制。在 AsA 的 C-5 处引入大块取代基(如碘苄氧基)可能并不适合设计类似物,因为这种类似物可能仍能保持 AsA 本身在体内的分布特性。