Photophysical Properties of Hydroxy-Substituted Flavothiones

Elisei, Fausto; Lima, João Carlos; Ortica, F.; Aloisi, Gian Gaetano; Costa, Manuela; Leitão, Emília; Abreu, Isabel A.; Dias, António; Bonifácio, Vasco D. B.; Medeiros, Jorge; Maçanita, António L.; Becker, Ralph S.

doi:10.1021/jp000084y

Cited by 22 publications

(62 citation statements)

References 14 publications

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“…The experimental errors on T were estimated to be about Ϯ10%, whereas those on T and T were Ϯ15%. The singlet oxygen yields ( ⌬ ) were determined by measuring the phosphorescence intensity of O 2 ( 1 ⌬ g ) with a germanium diode detector in air-equilibrated solutions (14,15) and by using phenalenone ( ⌬ ϭ 0.97) (16) as a reference.…”

Section: Photophysical Measurementsmentioning

confidence: 99%

Excited-state Properties and In Vitro Phototoxicity Studies of Three Phenothiazine Derivatives¶

Elisei¹,

Latterini²,

Aloisi³

et al. 2007

Photochemistry and Photobiology

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This work concerns a combined photophysical, photochemical and photobiological study of three drugs (psychotherapeutic agents) of the phenothiazine series: perphenazine, fluphenazine hydrochloride and thioridazine hydrochloride. The excited‐state properties were first investigated by stationary and time‐resolved fluorimetry and by laser flash photolysis. The spectral description was assisted by quantum‐mechanical calculations with the INDO/1‐CI method. In organic media the lowest excited singlet state was found to decay by fluorescence (small quantum yield) and mainly by intersystem crossing to the lowest triplet state, which is responsible for oxygen photosensitization (high yields of singlet oxygen production) and photodegradation. A further decay pathway in aqueous solutions was the photoionization process, which led to the formation of the phenothiazine radical cations and the solvated electron. After the preliminary study of the photobehavior in organic solvents and in water, the phototoxicity of the three drugs was investigated on various biological substrates through a series of in vitro assays under UVA irradiation. Photohemolysis of mouse erythrocytes and phototoxicity on cultured murine fibroblasts were observed for all three compounds. Lipid photoperoxidation was then investigated using linoleic acid as the unsaturated lipid model and isolated red blood cell membranes. The drug‐induced photodamage was also evaluated on proteins by measuring the photosensitizing cross‐linking in erythrocyte ghosts. The combined approach proved to be useful in understanding the mechanism by which these phenothiazine derivatives induce skin photosensitization. In particular, the photophysical properties of the compounds under investigation and the results of the study on their phototoxicity are in agreement with a mechanism that involves the radical cation of the drugs as a main intermediate.

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Section: Photophysical Measurementsmentioning

confidence: 99%

Excited-state Properties and In Vitro Phototoxicity Studies of Three Phenothiazine Derivatives¶

Elisei¹,

Latterini²,

Aloisi³

et al. 2007

Photochemistry and Photobiology

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“…The photophysical properties of these compounds were studied in some detail (1). Briefly, the consequences of replacing the carbonyl (CϭO) group of flavones by the thione (CϭS) group generally include (1) a large decrease in the energy of the n, * (1,3) and , * (1,3) states (leading to absorption of visible light); (2) the increase in the quantum yields of triplet formation ( T ) and singlet oxygen photosensitization ( ⌬ ); and (3) the appearance of photobiological activity and photochemistry under visible light irradiation (1).…”

Section: Formulamentioning

confidence: 99%

“…This study is part of a series of efforts with the ultimate goal of developing environmentally friendly photopesticides (1)(2)(3). Our strategy has been based on the search of chemical modifications of nontoxic, nonphototoxic, naturally occurring compounds, which may lead to still nontoxic but strongly photoactive derivatives.…”

Section: Introductionmentioning

confidence: 99%

“…Our strategy has been based on the search of chemical modifications of nontoxic, nonphototoxic, naturally occurring compounds, which may lead to still nontoxic but strongly photoactive derivatives. The desired characteristics are (1) high yield of solar absorption; (2) high yield of triplet formation and long triplet lifetimes; (3) the synthetically produced photosensitizer should be photochemically or thermally degraded into environmentally safe compounds under natural conditions; and (4) the phototoxic mechanism should not induce mutagenic effects. Flavothione (FT) and a series of hydroxy-substituted flavothiones were selected to implement this strategy.…”

Section: Introductionmentioning

confidence: 99%

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Photobiological Properties of Hydroxy-substituted Flavothiones¶

Borges¹,

Romão²,

Matos³

et al. 2002

Photochem Photobiol

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Flavothione (FT) and a series of 18 hydroxy- and methoxy-substituted flavothiones were screened for photobiological activity. The 5-hydroxy-substituted compounds (group 3) and the methoxy-substituted flavothiones were inactive. FT and the remaining hydroxy-substituted compounds, all displayed photobiological activity. Among these, the 3-hydroxy-substituted compounds (group 2) were the most efficient photosensitizers overall in spite of their concurrent fast photodegradation. FT and all other hydroxyflavothiones, not substituted in the 3- or 5-positions (group 1), were inefficient compared with group 2. Detailed photobiological tests were carried out for four flavothiones of groups 1 and 2. The biological tests included fungi, several strains of Escherichia coli, Salmonella typhimurium and mammalian cells. In addition, the ability of these flavothiones to perform lipid peroxidation was evaluated. FT and 6-hydroxyflavothione (group 1) induce DNA damage via H-atom abstraction from the lowest n, pi* triplet state of the thione (oxygen independent). For 3-hydroxy and 3,6-dihydroxyflavothione (group 2), both DNA and the membrane are targets. The mechanism likely involves both energy transfer and electron transfer from the lowest pi, pi* triplet state to oxygen, to form singlet oxygen and the superoxide anion. Some of these compounds could be considered as models for environmentally safe photopesticides.

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“…These are described by absorption and emission spectroscopy, triplet yield and life times. They are used as oxygen photosensitizes [4,5] and photobiological activities and also as green pesticides as they inhibit the growth of fungi, bacteria and mammalian cells. [6,7] In the mid-1950s, Baker synthesized FTs and isoflavothiones using phosphorus pentasulfide in dry benzene or xylene under reflux.…”

Section: Introductionmentioning

confidence: 99%

NMR of a series of novel hydroxyflavothiones

Nguyen

Nguyen²,

Kamounah

et al. 2009

Magnetic Reson in Chemistry

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Alkylated hydroxyflavothiones, namely flavothione, 5-hydroxyflavothione, 5,7-dihydroxyflavothione (chrysinthione), 7-dodecyloxy-5-hydroxyflavothione, 7-butyloxy-5-hydroxyflavothione, 2',3,4',7-tetramethoxy-5-hydroxyflavothione, 3,3',4',7-tetramethoxy-5-hydroxyflavothione, 7-butyloxy-4',5-dihydroxyflavothione and 7-butyloxy-4',5-hydroxyflavanonethione have been synthesized from the corresponding hydroxyflavones in two steps, alkylation of the non-hydrogen-bonded hydroxyl groups by bromoalkanes or dimethyl sulfate followed by conversion of the carbonyl group to a thione using Lawesson's Reagent under microwave irradiation and solvent-free conditions. Part of the alkylated flavanone, 7-butyloxy-4',5-dihydroxyflavanone, was oxidized during the treatment with Lawesson's reagent to yield a second product 7-butyloxy-4',5-dihydroxyflavothione in addition to the target product butyloxy-4',5-hydroxyflavanonethione. Deuterium isotope effects on 13C chemical shifts have been measured in hydroxyflavones, isoflavones, flavanones and the thio analogs. Formal four-bond deuterium isotope effects on 13C chemical shifts, nDeltaC=S(OD) are very sensitive to variations in structures and substitution patterns. Density functional theory (DFT) calculations are carried out to obtain geometries. Correlations relating distances around the hydrogen bond system to the deuterium isotope effects on 13C chemical shifts are discussed. 13C chemical shifts are calculated by DFT methods. Effects of thiocarbonyl anisotropies are suggested.

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Photophysical Properties of Hydroxy-Substituted Flavothiones

Cited by 22 publications

References 14 publications

Excited-state Properties and In Vitro Phototoxicity Studies of Three Phenothiazine Derivatives¶

Excited-state Properties and In Vitro Phototoxicity Studies of Three Phenothiazine Derivatives¶

Photobiological Properties of Hydroxy-substituted Flavothiones¶

NMR of a series of novel hydroxyflavothiones

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