Propriétés du premier état triplet de l'hypericine. Étude par spectroscopie laser

Jardon, Pierre; Lazorchak, N.; Gautron, R.

doi:10.1051/jcp/1986830311

Cited by 41 publications

(31 citation statements)

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“…Hypericin has a large triplet yield r0.70 in ethanol (Jardon et al, 1986)] and is capable of generating significant quantities of singlet oxygen (Meruelo et al, 1988Degar et al, 1992;Lenard et al, 1993). The virucidal activity of hypericin results, in part, from production of singlet oxygen.…”

mentioning

confidence: 99%

Roles of Oxygen and Photoinduced Acidification in the Light-Dependent Antiviral Activity of Hypocrellin A

Fehr¹,

Carpenter²,

Wannemuehler³

et al. 1995

Biochemistry

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Hypocrellin A displays photoinduced antiviral activity, in particular against the human immunodeficiency virus (HIV), as does its counterpart, hypericin. Although hypocrellin A, like hypericin, executes an excitedstate intramolecular proton transfer, it differs from hypericin in two important ways. Unlike hypericin, hypocrellin A absolutely requires oxygen for its antiviral activity. Also, whereas we have previously demonstrated that hypericin functions as a light-induced proton source, we do not observe that hypocrellin A acidifies its surrounding medium in the presence of light. These results are discussed in the context of the ground-and excited-state photophysics of hypericin and its mechanisms of photoinduced virucidal activity. ABSTRACT: Hypocrellin A displays photoinduced antiviral activity, in particular against the human immunodeficiency virus (HIV), as does its counterpart, hypericin. Although hypocrellin A, like hypericin, executes an excited-state intramolecular proton transfer, it differs from hypericin in two important ways. Unlike hypericin, hypocrellin A absolutely requires oxygen for its antiviral activity. Also, whereas we have previously demonstrated that hypericin functions as a light-induced proton source, we do not observe that hypocrellin A acidifies its surrounding medium in the presence of light. These results are discussed in the context of the ground-and excited-state photophysics of hypericin and its mechanisms of photoinduced virucidal activity.

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confidence: 99%

Roles of Oxygen and Photoinduced Acidification in the Light-Dependent Antiviral Activity of Hypocrellin A

Fehr¹,

Carpenter²,

Wannemuehler³

et al. 1995

Biochemistry

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“…potential of the normal [7,14] form of hypericin is not actually the appropriate one to be used in calculating ∆G°e t in eq 2. The correct reduction potential is that of the tautomer.…”

Section: Discussionmentioning

confidence: 99%

“…26 Here we report a study of the quenching of triplet hypericin ( 3 Hyp) by different amines in acetonitrile and by electron acceptors in dimethyl sulfoxide. We refine a previous rough estimate of the solution phase triplet energy (∼13 700 cm -1 in ethanol) 14 by using an appropriately chosen set of energy transfer acceptors. Photophysical properties and formation efficiency of Hyp •-and Hyp •+ radicals are reported, along with rate constants for a series of quenchers that give rise to these species.…”

Section: Chart 1 Tautomeric Forms Of Hypercinmentioning

confidence: 99%

“…NMR and X-ray crystallographic studies point out that among five energetically reasonable tautomers 6 the natural and most stable form of hypericin in the solid state and in aprotic solvents is the [7,14] tautomer (Chart 1). 7,8 Petrich et al established that in the excited singlet state hypericin undergoes tautomerization on the picosecond time scale after laser excitation in both protic and aprotic solvents.…”

Section: Introductionmentioning

confidence: 99%

“…Hypericin has been shown to have a high quantum yield of triplet formation (0.5-0.7), 14,15 and it efficiently generates singlet oxygen, 16 though this may not be the mechanism for its photodynamic action. Superoxide (O 2…”

Section: Introductionmentioning

confidence: 99%

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Quenching of Excited Triplet State Hypericin with Energy Acceptors and Donors and Acceptors of Electrons

and¹,

Jenks²,

and³

et al. 1999

J. Phys. Chem. B

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The quenching of the triplet state of hypericin by acceptors of electronic energy and donors and acceptors of electrons was studied by nanosecond laser photolysis. The energy of triplet hypericin is E T ) 13 350 cm -1 , and for acceptors with E T < 13 300 cm -1 the observed energy transfer rate constant declines with increasing exothermicity. Quenching of triplet hypericin by amines in acetonitrile and electron acceptors in DMSO occurs via electron transfer. Spectroscopic and kinetic properties and the quantum yield of hypericin radical ion formation were established. The rate constant profiles for electron transfer (in both directions) are consistent with an excited-state reaction occurring before electron transfer. The rate constant of the interaction of reduced hypericin with O 2 was estimated to be 3.8 × 10 8 M -1 s -1 in acetonitrile.

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Vom Photosensibilisator Hypericin zum Photorezeptor Stentorin – die Chemie der Phenanthroperylenchinone

Falk

1999

Angewandte Chemie

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Propriétés du premier état triplet de l'hypericine. Étude par spectroscopie laser

Cited by 41 publications

References 0 publications

Roles of Oxygen and Photoinduced Acidification in the Light-Dependent Antiviral Activity of Hypocrellin A

Roles of Oxygen and Photoinduced Acidification in the Light-Dependent Antiviral Activity of Hypocrellin A

Quenching of Excited Triplet State Hypericin with Energy Acceptors and Donors and Acceptors of Electrons

Vom Photosensibilisator Hypericin zum Photorezeptor Stentorin – die Chemie der Phenanthroperylenchinone

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