Inclusion complex formation of sanguinarine alkaloid with cucurbit[7]uril

Inhibition of nucleophilic attack and photooxidation

Z. Miskolczy, Mónika Megyesi, G. Tárkányi, Réka Mizsei, L. Biczók

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57 Citations (Scopus)

Abstract

The inclusion of sanguinarine, a biologically active natural benzophenanthridine alkaloid, in cucurbit[7]uril (CB7) was studied by NMR and ground-state absorption spectroscopy, as well as steady-state and time-resolved fluorescence measurements in aqueous solution. The iminium form of sanguinarine (SA+) produces very stable 1:1 inclusion complex with CB7 (K = 1.0 × 106 M-1), whereas the equilibrium constant for the binding of the second CB7 is about 3 orders of magnitude smaller. Marked fluorescence quantum yield and fluorescence lifetime enhancements are found upon encapsulation of SA+ due to the deceleration of the radiationless deactivation from the single-excited state, but the fluorescent properties of 1:1 and 1:2 complexes barely differ. The equilibrium between the iminium and alkanolamine forms is shifted 3.69 pK unit upon addition of CB7 as a consequence of the preferential encapsulation of the iminium form and the protection of the 6 position of sanguinarine against the nucleophilic attack by hydroxide anion. On the basis of thermodynamic cycle, about 225 M-1 is estimated for the equilibrium constant of the complexation between the alkanolamine form of sanguinarine (SAOH) and CB7. The confinement in the CB7 macrocycle can be used to impede the nucleophilic addition of OH- to SA+ and to hinder the photooxidation of SAOH.

Original languageEnglish
Pages (from-to)1061-1070
Number of pages10
JournalOrganic and Biomolecular Chemistry
Volume9
Issue number4
DOIs
Publication statusPublished - Feb 21 2011

Fingerprint

alkaloids
Photooxidation
photooxidation
Alkaloids
attack
Alkanolamines
inclusions
fluorescence
Fluorescence
Equilibrium constants
Encapsulation
thermodynamic cycles
Benzophenanthridines
deceleration
deactivation
hydroxides
Deceleration
absorption spectroscopy
Quantum yield
Complexation

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Biochemistry

Cite this

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title = "Inclusion complex formation of sanguinarine alkaloid with cucurbit[7]uril: Inhibition of nucleophilic attack and photooxidation",
abstract = "The inclusion of sanguinarine, a biologically active natural benzophenanthridine alkaloid, in cucurbit[7]uril (CB7) was studied by NMR and ground-state absorption spectroscopy, as well as steady-state and time-resolved fluorescence measurements in aqueous solution. The iminium form of sanguinarine (SA+) produces very stable 1:1 inclusion complex with CB7 (K = 1.0 × 106 M-1), whereas the equilibrium constant for the binding of the second CB7 is about 3 orders of magnitude smaller. Marked fluorescence quantum yield and fluorescence lifetime enhancements are found upon encapsulation of SA+ due to the deceleration of the radiationless deactivation from the single-excited state, but the fluorescent properties of 1:1 and 1:2 complexes barely differ. The equilibrium between the iminium and alkanolamine forms is shifted 3.69 pK unit upon addition of CB7 as a consequence of the preferential encapsulation of the iminium form and the protection of the 6 position of sanguinarine against the nucleophilic attack by hydroxide anion. On the basis of thermodynamic cycle, about 225 M-1 is estimated for the equilibrium constant of the complexation between the alkanolamine form of sanguinarine (SAOH) and CB7. The confinement in the CB7 macrocycle can be used to impede the nucleophilic addition of OH- to SA+ and to hinder the photooxidation of SAOH.",
author = "Z. Miskolczy and M{\'o}nika Megyesi and G. T{\'a}rk{\'a}nyi and R{\'e}ka Mizsei and L. Bicz{\'o}k",
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T2 - Inhibition of nucleophilic attack and photooxidation

AU - Miskolczy, Z.

AU - Megyesi, Mónika

AU - Tárkányi, G.

AU - Mizsei, Réka

AU - Biczók, L.

PY - 2011/2/21

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N2 - The inclusion of sanguinarine, a biologically active natural benzophenanthridine alkaloid, in cucurbit[7]uril (CB7) was studied by NMR and ground-state absorption spectroscopy, as well as steady-state and time-resolved fluorescence measurements in aqueous solution. The iminium form of sanguinarine (SA+) produces very stable 1:1 inclusion complex with CB7 (K = 1.0 × 106 M-1), whereas the equilibrium constant for the binding of the second CB7 is about 3 orders of magnitude smaller. Marked fluorescence quantum yield and fluorescence lifetime enhancements are found upon encapsulation of SA+ due to the deceleration of the radiationless deactivation from the single-excited state, but the fluorescent properties of 1:1 and 1:2 complexes barely differ. The equilibrium between the iminium and alkanolamine forms is shifted 3.69 pK unit upon addition of CB7 as a consequence of the preferential encapsulation of the iminium form and the protection of the 6 position of sanguinarine against the nucleophilic attack by hydroxide anion. On the basis of thermodynamic cycle, about 225 M-1 is estimated for the equilibrium constant of the complexation between the alkanolamine form of sanguinarine (SAOH) and CB7. The confinement in the CB7 macrocycle can be used to impede the nucleophilic addition of OH- to SA+ and to hinder the photooxidation of SAOH.

AB - The inclusion of sanguinarine, a biologically active natural benzophenanthridine alkaloid, in cucurbit[7]uril (CB7) was studied by NMR and ground-state absorption spectroscopy, as well as steady-state and time-resolved fluorescence measurements in aqueous solution. The iminium form of sanguinarine (SA+) produces very stable 1:1 inclusion complex with CB7 (K = 1.0 × 106 M-1), whereas the equilibrium constant for the binding of the second CB7 is about 3 orders of magnitude smaller. Marked fluorescence quantum yield and fluorescence lifetime enhancements are found upon encapsulation of SA+ due to the deceleration of the radiationless deactivation from the single-excited state, but the fluorescent properties of 1:1 and 1:2 complexes barely differ. The equilibrium between the iminium and alkanolamine forms is shifted 3.69 pK unit upon addition of CB7 as a consequence of the preferential encapsulation of the iminium form and the protection of the 6 position of sanguinarine against the nucleophilic attack by hydroxide anion. On the basis of thermodynamic cycle, about 225 M-1 is estimated for the equilibrium constant of the complexation between the alkanolamine form of sanguinarine (SAOH) and CB7. The confinement in the CB7 macrocycle can be used to impede the nucleophilic addition of OH- to SA+ and to hinder the photooxidation of SAOH.

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