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Redox and debromination reactions of brominated hypericin
Author(s) -
Eriksson Emma S. E.,
Guedes Rita C.,
Eriksson Leif A.
Publication year - 2008
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.21689
Subject(s) - chemistry , hypericin , anthracene , photochemistry , bromine , molecule , redox , aqueous solution , density functional theory , computational chemistry , organic chemistry , medicine , pharmacology
Phototoxic and radical‐generating debromination reactions of monobrominated hypericin with bromine at one of four possible positions were investigated using density functional theory. The study was performed on two closely lying conformational isomers, differing in the relative orientations of the two anthracene units of the hypericin core. Calculated adiabatic electron affinities show that the molecules have the ability to, in aqueous solution, extract an electron from the surrounding. The electron might then be passed on to molecular oxygen, forming reactive superoxide radical anions. If electron extraction from the molecule does not occur in this step, the molecule might dissociate, generating a negatively charged bromine as a leaving group and a hypericin radical capable of forming direct binding to biological molecules. This reaction was found possible for those species substituted by Br at two of the four positions, with barriers of ∼13 kcal/mol in aqueous solution. Debromination was not found energetically possible for neither the neutral ground state compounds nor the bay‐deprotonated species. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008