Abstract
A procedure for radioiodination of colchicine with iodineโ125 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^Iโcolchicine (^125^IโCol). Using 3.7โMBq of Na^125^I, 1.25โmM of colchicine as substrate, 1.1โmM of chloramineโT (CAT) as oxidizing agent in ethanol at 60ยฐC for 5โmin, a maximum radiochemical yield of ^125^IโCol (60%) was obtained. The specific activity of ^125^IโCol obtained was 44.4โMBq/0.5โmmol, and the labeled compound was not completely separated and purified from Col by means of highโpressure liquid chromatography (HPLC), so the uncertainty in the purity may affect the distribution and clearance routes due to the expected competition between ^125^IโCol and Col. The biological distribution in normal mice indicates the suitability of radioiodinated colchicine for imaging of muscles. Copyright ยฉ 2008 John Wiley & Sons, Ltd.