Synthesis and evaluation of [123I] iodoquercetin and [123I] iodocatechin as radical seeking agents

Free radicals are thought to be involved in processes such as central nervous system disorder, cardiovascular injury, inflammation, cancer, aging, and so on. Polyphenols, which are the active ingredients in tea, are known to scavenge various kinds of free radicals. Therefore, radioiodinated quercetin and catechin may help us elucidate relationships between the radicals and the incidence of the diseases. Precursors for radiolabeling were prepared from protection of the hydroxyl groups, iodination and stannylation of quercetin and cetechin. [123I]Iodinated quercetin and catechin were prepared by the reaction of the stannylated precursors with Na123I in the presence of chloramine-T followed by deprotection. After HPLC purification, (123I)iodoquercetin was incubated at 37 .deg. C two sets of mediums containing the unactivated (control) and activated U937 cell lines, respectively. Based on our NMR data, the site of iodination was either at C6 or C8 in the A ring, the latter being more likely. Radiochemical yields of the radiotracers ranged from 30 to 40% and radiochemical purity was greater than 99%. Higher uptake of [123I] iodoquercetin was observed in the activated system which is known to generate the hydrogen peroxide and other free radicals, compared to the control (1:4:1). Radioiodinated quercetin and catechin were prepared in high radiochemical yield and showed a distinguishable uptake pattern between control and activated cell systems. Further biological evaluation is currently underway