Facile Synthesis and Radioiodine Labeling of Hypericin

Hypericin (1,3,4,6,8,13-hexahydroxy-10,11-dimethylphenanthro[1,10,9,8-opqra]perylene- 7,14-dione), an antidepressant which is also known to be a potent protein kinase C (PKC) inhibitor was synthesized as a precursor for radioiodine labeling via two step reactions. Malignant glioma cells express higher PKC activity compared to untransformed glial cell. Here we report the synthesis and radioiodine labeling of hypericin as a potential brain tumor imaging radiopharmaceutical. The reference compound, 2-iodohypericin, and its radiolabelled analogues, 2-[¹²³I]iodohypericin and 2-[¹²⁴I]iodohypericin have been prepared by the reaction of hypericin with NaI or [¹²³I]NaI or [¹²⁴I]NaI. The labeling yield was 60-65% for each analogue and the optimal reaction time was 10 min. The purification and isolation of the labelled products were achieved by a reversedphase HPLC