Synthesis, characterization and photodynamic activity of amino-substituted hypocrellin derivatives

Blue light induced reactive oxygen species from flavin mononucleotide and flavin adenine dinucleotide on lethality of HeLa cells

Photodynamic therapy (PDT) is a safe and non-invasive treatment for cancers and microbial infections. Various photosensitizers and light sources have been developed for clinical cancer therapies. Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) are the cofactor of enzymes and are used as photosensitizers in this study. Targeting hypoxia and light-triggering reactive oxygen species (ROS) are experimental strategies for poisoning tumor cells in vitro. HeLa cells are committed to apoptosis when treated with FMN or FAD and exposed to visible blue light (the maximum emitted wavelength of blue light is 462nm). Under blue light irradiation at 3.744J/cm² (=0.52mW/cm² irradiated for 2h), the minimal lethal dose is 3.125μM and the median lethal doses (LD₅₀) for FMN and FAD are 6.5μM and 7.2μM, respectively. Individual exposure to visible blue light irradiation or riboflavin photosensitizers does not produce cytotoxicity and no side effects are observed in this study. The western blotting results also show that an intrinsic apoptosis pathway is activated by the ROS during photolysis of riboflavin analogues. Blue light triggers the cytotoxicity of riboflavins on HeLa cells in vitro. Based on these results, this is a feasible and efficient of PDT with an intrinsic photosensitizer for cancer research.

Perylenequinones: Isolation, Synthesis, and Biological Activity

The perylenequinones are a novel class of natural products characterized by pentacyclic conjugated chromophore giving rise to photoactivity. Potentially useful light-activated biological activity, targeting protein kinase C (PKC), has been identified for several of the natural products. Recently discovered new members of this class of compound, as well as several related phenanthroperylenequinones, are reviewed. Natural product modifications that improve biological profiles, and avenues for the total synthesis of analogs, which are not available from the natural product series, are outlined. An overview of structure/function relationships is provided.

Novel surfactant-like hypocrellin derivatives to achieve simultaneous drug delivery in blood plasma and cell uptake

Water-soluble derivatives of hypocrellins can be safely delivered in blood plasma but lose their photodynamic activity in vivo due to poor cell uptake, while hydrophobic derivatives retaining their activity may aggregate in the blood plasma and block vascular networks. Considering both drug delivery and biological activity, surfactant-like hypocrellin B (HB) derivatives, sodium 12-2-HB-aminododecanoate (SAHB) and sodium 11,11'-5,8-HB-dimercaptoundecanoate (DMHB), were first designed and then synthesized in the current work. Both SAHB and DMHB were photoactive, generating free radicals and reactive oxygen species, as confirmed by EPR and chemical measurements. Most importantly, DMHB was not only readily soluble, allowing preparation of an intravenous injection solution at a clinically acceptable concentration, but it was also more photodynamic therapy (PDT) active to human breast carcinoma MCF-7 cells than its parent HB under irradiation. The photodynamic activity was exactly identical to the (1)O(2) quantum yield and was not reduced by the improved water solubility, suggesting an independent hydrophilicity or lipophilicity. To our knowledge, this is a new strategy that possesses general significance for converting hydrophobic photosensitizers into clinically usable PDT drugs.

Synthesis and Characterization of Three Novel Amphiphilic Aminated Hypocrellins as Photodynamic Therapeutic Agents¶

To improve the amphiphilicities and red absorption of the hypocrellins, three novel 2-amino-2-demethoxy-hypocrellins were synthesized by the mild reactions of hypocrellin B with 4-(2-amino-ethyl)morpholine, N,N-dimethylethylenediamine and 1-(2-amino-ethyl)piperazine, respectively. The structures of these derivatives were characterized with proton nuclear magnetic resonance, infrared and mass spectra (MS). The ultraviolet-visible absorption and fluorescence spectra of the derivatives were measured and the new amino-substituted hypocrellins showed strong absorption in the domain of the phototherapeutic window (600-900 nm). Their amphiphilicities evaluated via the partition coefficients between n-octanol and phosphate-buffered saline buffer improved remarkably. Electron paramagnetic resonance spin-trapping measurements were used to investigate the photodynamic action of the three compounds in the presence of oxygen. Singlet oxygen (1O2) and superoxide anion radical (O2.-) generated by illuminating the hypocrellin derivatives in aerobic solution were observed.