Toward hypericin-derived potential photodynamic therapy agents |
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Authors: | Obermüller R A Hohenthanner K Falk H |
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Institution: | Institute of Chemistry, Johannes Kepler University, Altenbergerstrasse 69, A 4040 Linz, Austria. |
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Abstract: | To optimize a hypericin derivative as a potential photodynamic therapy agent its light-induced singlet oxygen/superoxide radical formation capability should be enhanced and its long-wavelength absorption band should be bathochromically shifted to better match medicinal lasers. A heavy-atom-substituted derivative was realized by electrophilic iodination of hypericin to yield 2,5-diiodo-hypericin. Using photodestruction of bilirubin IX alpha this derivative was demonstrated to exhibit an enhanced light-induced singlet oxygen/superoxide radical formation capability as compared to hypericin. With respect to a bathochromically shifted derivative styryl residues were attached to the methyl groups of hypericin by de novo ring synthesis. Although the long-wavelength absorption band of this derivative displayed a bathochromic shift of nearly 40 nm it unfortunately immediately underwent an intramolecular 2 + 2] cycloaddition to yield the corresponding cyclobutane derivative in which the added conjugation system became interrupted. |
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