Dramatic Improvements in Viral Inactivation With Brominated Psoralens, Naphthalenes and Anthracenes

Abstract

Amino or polyamino derivatives of naphthalene (N-H), anthracene (A-H) and 8-alkoxypsoralen (PSR-H) were prepared along with their monobrominated analogs (N-Br, A-Br and PSR-Br). The ammonium salts of these compounds are all water soluble and bind strongly to calf thymus DNA and to lambda phage, a double-helical DNA, protein-coated virus. Binding of the sensitizer to DNA occurs, presumably by a mixture of hydrophobic, intercalative and electrostatic interactions. Relative binding constants to calf thymus DNA and to lambda phage were measured by the ethidium bromide fluorescence quenching assay. In general the brominated analogs bind more tightly to calf thymus DNA and to the virus than to the nonhalogenated analogs. It is demonstrated that the brominated aromatics are much more effective at inactivating lambda phage upon photoactivation (lambda approximately 310 or 350 nm) than are their nonbrominated analogs. At identical sensitizer concentrations (by weight) and light flux N-Br, A-Br, and PSR-Br produce 5-6 more logs of viral inactivation than their nonbrominated counterparts (N-H, A-H and PSR-H, respectively). The bromine effect may originate from light-induced electron transfer and subsequent cleavage of the C-Br bond of the sensitizer radical anion bonds to form aryl radicals. Singlet oxygen cannot be responsible for the viral inactivation because the brominated sensitizers are equally effective in the presence and absence of oxygen. Dithiothreitol does not protect lambda phage from light-induced inactivation by the brominated sensitizer thereby demonstrating that the photogenerated reactive intermediates responsible for the effect are complexed to the virus and are not generated free in solution.

Inactivation of viruses in human cellular blood components

“…Recently, several groups have reported the synthesis of novel psoralens with greatly enhanced pathogen inactivation activity and reduced mutagenicity. Rai, Yerram and colleagues have reported the synthesis of brominated psoralens (PSR-Br) which appear to have improved activity compared to AMT and 8-MOP [38,39]. However, most of these studies have been carried out with non-pathogenic viral targets and require confirmation with cell-free and cell-associated targets.…”

Reactions of Psoralen Radical Cations with Biological Substrates†¶

“…Recent work from our laboratory (24,25) and from other groups (26)(27)(28)(29)(30)(31) has investigated the potential role of electron transfer chemistry, and in particular radical cations, in psoralen photochemistry. We have demonstrated that the 8deoxyguanosine; GMP, guanosine 5Ј-monophosphate; HPLC, high-performance liquid chromatography; LC/MS, liquid chromatography/mass spectrometry; 7-MC, 7-methoxycoumarin; 8-MOP, 8-methoxypsoralen; PUVA, psoralen plus UVA irradiation; SCE, saturated calomel electrode; TMP, thymidine 5Ј-monophosphate; 4,5Ј,8-TMP, 4,5Ј,8-trimethylpsoralen.…”

Photoionization and Photosensitized Electron-Transfer Reactions of Psoralens and Coumarins

“…Considerable research efforts have been directed toward identifying the excited-state intermediates involved in the photocycloaddition chemistry of psoralens that are used in PUVA. Early attention focused on characterization of the triplet states of 8-MOP and other psoralens by transient absorption spectroscopy 8 and the measurement of singlet oxygen yields. − A number of coumarin photosensitizers have also attracted attention since they do not form diadducts and can serve as models for the initial furan monoadduct that is the precursor to DNA cross-links. − More recently, the importance of binding to proteins, cycloaddition reactions with unsaturated fatty acids, , and electron-transfer reactions ,− in psoralen photochemistry has been examined. A detailed understanding of the molecular basis for both the therapeutic and harmful effects of PUVA therapy is obviously required to aid in the further development of potential new therapeutic agents.…”

“…[9][10][11][12][13][14][15][16] A number of coumarin photosensitizers have also attracted attention since they do not form diadducts and can serve as models for the initial furan monoadduct that is the precursor to DNA cross-links. [17][18][19] More recently, the importance of binding to proteins, 20 cyclo-addition reactions with unsaturated fatty acids, 21,22 and electrontransfer reactions 19,[23][24][25][26][27] in psoralen photochemistry has been examined. A detailed understanding of the molecular basis for both the therapeutic and harmful effects of PUVA therapy is obviously required to aid in the further development of potential new therapeutic agents.…”