Formation d'oxygène singulet <sub>1</sub>Δ<sub>g</sub> photosensibilisée par l'hypéricine. Étude cinétique en milieu micallaira non ionique

Racinet, Hélène; Gautron, Pierre JardonRene; Gautron, R.

doi:10.1051/jcp/1988850971

Cited by 90 publications

(52 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…8,9,11,12 The retention of toxicity in the absence of oxygen excludes unique assignment of antiviral activity to the trivial generation of singlet oxygenseven though hypericin does generate triplets in high yield. [25][26][27][28] (20 The instrument response of the 30-Hz and 2-kHz systems are determined, respectively, by means of the ground-state bleach of nile blue and the stimulated emission of coumarin 500 on a daily basis. On a picosecond time scale, nile blue has an instantaneous bleach.…”

Section: Methodsmentioning

confidence: 99%

Excited-State Photophysics of Hypericin and Its Hexamethoxy Analog: Intramolecular Proton Transfer as a Nonradiative Process in Hypericin

et al. 1997

View full text Add to dashboard Cite

The excited-state photophysics of the light induced antiviral agent, hypericin, are compared with those of its methylated analog, hexamethoxyhypericin. This comparison is instructive in understanding both the groundand the excited-state properties of hypericin. That the hexamethoxy analog has no labile protons that can be transferred, that it cannot protonate its own carbonyl groups, that it has a reduced fluorescence quantum yield and lifetime with respect to hypericin, and that it exhibits no stimulated emission or, more specifically, rise time in stimulated emission completely support our emerging model of the hypericin photophysics. The results are consistent with the presence of intramolecular excited-state proton transfer in hypericin but not in its methylated analog. DisciplinesChemistry | Organic Chemistry | Other Chemistry | Polymer Chemistry CommentsReprinted (adapted) with permission from Journal of American Chemical Society, 119 (13) Abstract:The excited-state photophysics of the light induced antiviral agent, hypericin, are compared with those of its methylated analog, hexamethoxyhypericin. This comparison is instructive in understanding both the ground-and the excited-state properties of hypericin. That the hexamethoxy analog has no labile protons that can be transferred, that it cannot protonate its own carbonyl groups, that it has a reduced fluorescence quantum yield and lifetime with respect to hypericin, and that it exhibits no stimulated emission or, more specifically, rise time in stimulated emission completely support our emerging model of the hypericin photophysics. The results are consistent with the presence of intramolecular excited-state proton transfer in hypericin but not in its methylated analog. IntroductionInterest in the polycyclic quinone, hypericin ( Figure 1a) was spawned by the discovery that it possesses extremely high toxicity toward certain viruses, including HIV and that this toxicity absolutely requires light. [1][2][3] Hypericin is also very similar in structure to the stentorin chromophore that confers phototactic and photophobic responses to protozoan ciliates. 4 The interaction of light with hypericin and hypericin-like chromophores is clearly of fundamental biological importance. In order to understand and eventually to exploit these properties of hypericin, it is essential to elucidate its nonradiative excitedstate processes. We have undertaken this task using the tools of ultrafast time-resolved absorption spectroscopy and have presented our results in a series of articles. [5][6][7][8][9][10][11][12][13] The argument for the presence of intramolecular excited-state proton transfer in hypericin is as follows. The hypericin analog

show abstract

Section: Methodsmentioning

confidence: 99%

Excited-State Photophysics of Hypericin and Its Hexamethoxy Analog: Intramolecular Proton Transfer as a Nonradiative Process in Hypericin

et al. 1997

View full text Add to dashboard Cite

show abstract

“…Exposure to light and the presence of oxygen result in tissue damage through development of oxygen radicals (5). Hypericin is a hydroxylated phenanthroperylenequinone derivate and is found in plants of the species Hypericum (5,6). The most common species is Hypericum perforatum (5).…”

Section: Introductionmentioning

confidence: 99%

“…The most common species is Hypericum perforatum (5). Hypericin produces singlet oxygen efficiently after light irradiation with a quantum yield of 0.73 (5,6).…”

Section: Introductionmentioning

confidence: 99%

In vitro photodynamic therapy of childhood rhabdomyosarcoma

Seitz

Warmann²,

Armeanu³

et al. 2007

Int J Oncol

View full text Add to dashboard Cite

Abstract. Treatment of childhood rhabdomyosarcoma is limited by recurrent disease and the development of multidrug resistance. Therefore, novel treatment options are desirable. Photodynamic therapy (PDT) using the photodynamic agent hypericin is proposed as an alternative approach for intraoperative visualization and treatment of this disease. The aim of this study was to investigate in vitro effects of hypericin on childhood rhabdomyosarcoma and to evaluate photodynamic therapy as a possible basis for treatment. Rhabdomyosarcoma cells and fibroblasts (control) were incubated with increasing concentrations of hypericin. In vitro uptake and visualization of hypericin was evaluated by fluorescence microscopy and FACS. For photodynamic therapy, cells were exposed to white light for different time periods. Cytopathologic effects were assessed using standard histology. Cancer cells were investigated for cell viability (MTT assay), proliferative activity (Ki-67 assay), and apoptosis (TUNEL test). A 100% uptake of hypericin was found within the population of rhabdomyosarcoma cells. Uptake of hypericin in the fibroblasts was much less than in rhabdomyosarcoma cells. Hypericin without exposure to white light had no effect on tumor cell viability. After irradiation, PDT resulted in a nearly complete inhibition of cell proliferation of rhabdomyosarcoma cells with a corresponding increase in the frequency of apoptosis. In fibroblasts, PDT was less effective compared to tumor cells. Our data suggest hypericin as a novel tool for visualization and photodynamic therapy of childhood rhabdomyosarcoma. IntroductionRhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. About two thirds of all sarcomas and 7-8% of all solid malignant tumors in childhood are rhabdomyosarcomas (1). The two main histopathological subtypes of this malignancy in children are embryonal and alveolar RMS (2). Specific genetic alterations (3) such as the translocation t(2;13)(q35;q14) which occurs in 55% of all cases and t(1;13)(p36;q14) in 22% contribute to the diagnosis of alveolar RMS (1). No specific genetic alterations are found in embryonal rhabdomyosarcomas (1).The prognosis of these tumors is still poor and therapy is limited due to recurrent disease, development of metastases and multidrug resistance. Radical surgery plays a key role for the prognosis of these tumors. Mutilating surgery is often necessary for survival. Surgical procedures are complicated due to a lack of possible visualization of these tumors in vivo.In vivo visualization of childhood rhabdomyosarcoma can be performed using fluorescent proteins. Tumors and their behaviour can be studied in vivo using this imaging tool (4). Up to now, fluorescent proteins are mainly a basic research tool and have not been used in humans. Therefore, the investigation of other treatment modalities is of increasing interest.Photodynamic therapy (PDT) can be performed after local or systemic administration of a photodynamic drug. Exposure to light and the presence of oxygen result in...

show abstract

“…59 The mechanism of cytotoxicity most probably involves the generation of singlet oxygen by the light-excited photosensitizer. 60,61 Hypericin produces singlet oxygen very efficiently (with a quantum yield of 0.73 62 ), and singlet oxygen is most probably involved in hypericin-mediated killing of tumor cells in vitro. 56 Other studies have suggested that the antiviral activity of hypericin is due to the production of singlet oxygen.…”

Section: Antiviral Activity Of Hypericinmentioning

confidence: 99%

Research at the Interface between Chemistry and Virology: Development of a Molecular Flashlight

et al. 1996

View full text Add to dashboard Cite

Although industrial researchers have been involved in interdisciplinary studies pertaining to virology for several decades, the participation of academic chemists has been significantly increased owing to the importance of HIV (human immunodeficiency virus), the virus which leads to the onset of AIDS (acquired immune deficiency syndrome). The Center for Disease Control estimates that almost 20 million people have been infected by HIV worldwide. The compelling need for effective antiviral therapies for HIVinfected persons, together with rapid advances in understanding the molecular mechanisms of virus replication, has resulted in an explosion of interest in antiviral agents and approaches to antiviral therapies DisciplinesChemistry | Environmental Chemistry | Inorganic Chemistry | Organic Chemistry | Other Chemistry | Polymer Chemistry CommentsReprinted (adapted) with permission from Chemical Reviews, 96(1); 523-536.

show abstract

Formation d'oxygène singulet ₁Δ_g photosensibilisée par l'hypéricine. Étude cinétique en milieu micallaira non ionique

Cited by 90 publications

References 0 publications

Excited-State Photophysics of Hypericin and Its Hexamethoxy Analog: Intramolecular Proton Transfer as a Nonradiative Process in Hypericin

Excited-State Photophysics of Hypericin and Its Hexamethoxy Analog: Intramolecular Proton Transfer as a Nonradiative Process in Hypericin

In vitro photodynamic therapy of childhood rhabdomyosarcoma

Research at the Interface between Chemistry and Virology: Development of a Molecular Flashlight

Contact Info

Product

Resources

About

Formation d'oxygène singulet 1Δg photosensibilisée par l'hypéricine. Étude cinétique en milieu micallaira non ionique

Cited by 90 publications

References 0 publications

Excited-State Photophysics of Hypericin and Its Hexamethoxy Analog: Intramolecular Proton Transfer as a Nonradiative Process in Hypericin

Excited-State Photophysics of Hypericin and Its Hexamethoxy Analog: Intramolecular Proton Transfer as a Nonradiative Process in Hypericin

In vitro photodynamic therapy of childhood rhabdomyosarcoma

Research at the Interface between Chemistry and Virology: Development of a Molecular Flashlight

Contact Info

Product

Resources

About

Formation d'oxygène singulet ₁Δ_g photosensibilisée par l'hypéricine. Étude cinétique en milieu micallaira non ionique