An investigation of the ¹²⁵I‐radioiodination of colchicine for medical purposes

Abstract

Abstract A procedure for radioiodination of colchicine with iodine‐125 is carried out via an electrophilic substitution reaction. The reaction parameters studied were colchicine concentration, pH of the reaction mixture, reaction time, temperature, different oxidizing agents and different organic media to optimize the conditions for the labeling of colchicine and to obtain a high radiochemical yield of the 125 I‐colchicine ( 125 I‐Col). Using 3.7 MBq of Na 125 I, 1.25 mM of colchicine as substrate, 1.1 mM of chloramine‐T (CAT) as oxidizing agent in ethanol at 60°C for 5 min, a maximum radiochemical yield of 125 I‐Col (60%) was obtained. The specific activity of 125 I‐Col obtained was 44.4 MBq/0.5 mmol, and the labeled compound was not completely separated and purified from Col by means of high‐pressure liquid chromatography (HPLC), so the uncertainty in the purity may affect the distribution and clearance routes due to the expected competition between 125 I‐Col and Col. The biological distribution in normal mice indicates the suitability of radioiodinated colchicine for imaging of muscles. Copyright © 2008 John Wiley & Sons, Ltd.