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

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 I-125-Colchicine (I-125-Col). Using 3.7 MBq of (NaI)-I-125, 1.25 mM of colchicine as substrate, 1.1 mM of chloramine-T (CAT) as oxidizing agent in ethanol at 60 degrees C for 5 min, a maximum radiochemical yield of I-125-Col (60\%) was obtained. The specific activity of I-125-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 I-125-Col and Col. The biological distribution in normal mice indicates the suitability of radioiodinated colchicine for imaging of muscles.