Cyclodextrins modify the proton transfer photoreactions of norharmane

Prados, José L.; León, Andrés G.; Olives, Ana I.; Martín, M. Antonia; Castillo, B. del

doi:10.1016/j.jphotochem.2005.04.007

Cited by 9 publications

(14 citation statements)

References 31 publications

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“…Inclusion complexes of some β-carboline alkaloids with β-CD have been already described in the literature. − In these studies, the β-CDs exerted a significant influence on the proton transfer of some β-carboline derivatives. In the presence of β-CD, access of the protons to the pyridinic nitrogen was not possible due to the lower diffusion rate of protons inside these cavities with a lower polarity than water, decreasing the basicity of these organic bases.…”

Section: Resultsmentioning

confidence: 95%

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The Impact of Dihydrogen Phosphate Anions on the Excited-State Proton Transfer of Harmane. Effect of β-Cyclodextrin on These Photoreactions

et al. 2011

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Photoinduced proton transfer reactions of harmane (1-methyl-9H-pyrido[3,4-b]indole) (HAR) in the presence of a proton donor/acceptor such as dihydrogen phosphate anions in aqueous solution have been studied by stationary and time-resolved fluorescence spectroscopy. The presence of high amounts of dihydrogen phosphate ions modifies the acid/base properties of this alkaloid. Thus, by keeping the pH constant at pH 8.8 and by increasing the amount of NaH(2)PO(4) in the solution, it is possible to reproduce the same spectral profiles as those obtained in high alkaline solutions (pH >12) in the absence of NaH(2)PO(4). Under these conditions, a new fluorescence profile appears at around 520 nm. This result could be related to the results of a recent investigation which suggests that a high intake of phosphates may promote skin tumorigenesis. The presence of β-cyclodextrin (β-CD) avoids the proton transfer reactions in this alkaloid by means the formation of an inclusion complex between β-CD and HAR. The formation of this complex originates a remarkable enhancement of the emission intensity from the neutral form in contrast to the cationic and zwitterionic forms. A new lifetime was obtained at 360 nm (2.5 ns), which was associated with the emission of this inclusion complex. At this wavelength, the fluorescence intensity decay of HAR can be described by a linear combination of two exponentials. From the ratio between the pre-exponential factors, we have obtained a value of K = 501 M for the equilibrium of formation of this complex.

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Section: Resultsmentioning

confidence: 95%

“…On the other hand, it is known − some β-carboline derivatives form inclusion complexes with the β-cyclodextrin (β-CD). The formation of inclusion complexes between HAR and β-CD reduces the number of species in aqueous solution, and this could help us understand the formation mechanisms of all of these species.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Dihydrogen Phosphate Anions on the Excited-State Proton Transfer of Harmane. Effect of β-Cyclodextrin on These Photoreactions

et al. 2011

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“…Surfactants, because of their ability to solubilize membrane proteins, are extremely important in simulating the complex environmental condition present in larger bioaggregates such as biological membranes. − The wide range of functions performed by the biological membranes and membrane proteins have motivated researchers to look for simple model systems. A typical example of such membrane mimetic models is a micelle, which is an organized assembly of surfactants in aqueous media. , Interest in this subject has received remarkable attention in recent years, with explosive growth in research on various bioactive molecules that are promising against a variety of diseases including cancer. − The structure and function of these biologically active molecules have drawn the attention of researchers because of their ability to achieve specific chemical efficiency as a result of organization in reaction media. For a particular prototropic probe, it is often necessary to opt for one prototopic form or a desired composition of the different prototropic species to achieve better efficiency for a targeted purpose in a specific environment.…”

Section: Introductionmentioning

confidence: 99%

Surfactant Chain-Length-Dependent Modulation of the Prototropic Transformation of a Biological Photosensitizer: Norharmane in Anionic Micelles

et al. 2007

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A photophysical study of norharmane (NHM), an efficient cancer cell photosensitizer, has been undertaken in well-characterized biomimetic micellar nanocavities formed by anionic surfactants of varying chain length, namely, sodium decyl sulfate (S10S), sodium dodecyl sulfate (S12S), and sodium tetradecyl sulfate (S14S), using steady-state and time-resolved fluorescence spectroscopy. The effect of the hydrophobic chain length on the structural dynamism of the fluorophore has been reported. Experimental results demonstrate that the equilibrium of this dynamism is sensitive to the environment. Variation in the surfactant chain length plays an important role in promoting a specific prototropic form of the probe molecule. A striking feature of the present study is that an increase in the surfactant chain length (hydrophobicity) favors the cationic species of NHM. This has been rationalized on the basis of changes in the local pH and the aggregation number of the micelles. A fluorescence quenching study of the micelle-bound probe using ionic quencher Cu2+ corroborates this.

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“…The high electronic density and low polarity afforded by CDs cavities modify the spectral characteristics of the included molecules and therefore shifts in the excitation and emission wavelengths and increases in the fluorescence intensity should be expected as a consequence of the inclusion process .…”

Section: Resultsmentioning

confidence: 99%

Spectrofluorimetric determination of the antineoplastic agent lomustine based on the sensitizing effect of β‐cyclodextrin

2015

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The effects of solvent dipolarity/polarizability and solvent-solute hydrogen bonding on the photophysical properties of the antineoplastic drug lomustine were analysed by means of the linear solvation energy relationship (LSER) concept proposed by Kamlet and Taft. The LSER method enabled the overall solvent effects to be quantitatively estimated and separated into specific and non-specific contributions. The molecular encapsulation of lomustine by β-cyclodextrin (β-CD) has been studied using fluorescence spectroscopy. The results are discussed in terms of the binding parameter and the effect of the solvent used. It was concluded that β-CD forms a 1:1 inclusional complex with lomustine in acetonitrile solution and its association constant was calculated to be 500 M(-1). In addition, and for the first time, a simple, rapid and high sensitive fluorimetric method for the determination of lomustine was developed based upon the enhancement effect produced through complex formation with β-CD. The new approach for the quantification of lomustine in the presence of β-CD was described in aqueous and organic solutions. Better limits of detection (0.31 µg ml(-1)) and quantification (1.05 µg ml(-1)) were obtained in aqueous solution with respect to those obtained in organic solvent.

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Cyclodextrins modify the proton transfer photoreactions of norharmane

Cited by 9 publications

References 31 publications

The Impact of Dihydrogen Phosphate Anions on the Excited-State Proton Transfer of Harmane. Effect of β-Cyclodextrin on These Photoreactions

The Impact of Dihydrogen Phosphate Anions on the Excited-State Proton Transfer of Harmane. Effect of β-Cyclodextrin on These Photoreactions

Surfactant Chain-Length-Dependent Modulation of the Prototropic Transformation of a Biological Photosensitizer: Norharmane in Anionic Micelles

Spectrofluorimetric determination of the antineoplastic agent lomustine based on the sensitizing effect of β‐cyclodextrin

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