PH-Dependent Multistate System Generated by a Synthetic Furanoflavylium Compound: An Ancestor of the Anthocyanin Multistate of Chemical Species

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Abstract

The multistate of chemical species generated by 4′-hydroxy-3,2′-furanoflavylium is similar to that of anthocyanins and related compounds. This furanoflavylium multistate system was fully characterized by UV-visible and NMR spectroscopy, allowing determination of the respective equilibrium and rate constants. In contrast to the multistate generated by flavylium cations derived from anthocyanins and related compounds, the furanoflavylium multistate is characterized by much slower hydration and tautomerization (pyran ring opening-closing). In addition, the cis-trans isomerization of the chalcones of this system (2′-hydroxyaurones) is extremely slow when compared with anthocyanins. The observed similar order of magnitude for tautomerization and isomerization rate constants leads to peculiar kinetics from the flavylium cation (pH = 1) to the stable trans-chalcone (higher pH values). The hemiketal appears and disappears during the first stages of the kinetics, which gives the intermediate cis-chalcone (pseudo-equilibrium). This last species disappears in a much slower process, as fully characterized by 1 H NMR, to give the final trans-chalcone.

Original languageEnglish
Pages (from-to)4091-4100
Number of pages10
JournalACS Omega
Volume4
Issue number2
DOIs
Publication statusPublished - 22 Feb 2019

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Anthocyanins
Chalcone
Isomerization
Cations
Rate constants
Positive ions
Chalcones
Pyrans
Kinetics
Equilibrium constants
Hydration
Nuclear magnetic resonance spectroscopy
Nuclear magnetic resonance

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@article{6486b6fb4a654135b8df57c23b64ff78,
title = "PH-Dependent Multistate System Generated by a Synthetic Furanoflavylium Compound: An Ancestor of the Anthocyanin Multistate of Chemical Species",
abstract = "The multistate of chemical species generated by 4′-hydroxy-3,2′-furanoflavylium is similar to that of anthocyanins and related compounds. This furanoflavylium multistate system was fully characterized by UV-visible and NMR spectroscopy, allowing determination of the respective equilibrium and rate constants. In contrast to the multistate generated by flavylium cations derived from anthocyanins and related compounds, the furanoflavylium multistate is characterized by much slower hydration and tautomerization (pyran ring opening-closing). In addition, the cis-trans isomerization of the chalcones of this system (2′-hydroxyaurones) is extremely slow when compared with anthocyanins. The observed similar order of magnitude for tautomerization and isomerization rate constants leads to peculiar kinetics from the flavylium cation (pH = 1) to the stable trans-chalcone (higher pH values). The hemiketal appears and disappears during the first stages of the kinetics, which gives the intermediate cis-chalcone (pseudo-equilibrium). This last species disappears in a much slower process, as fully characterized by 1 H NMR, to give the final trans-chalcone.",
author = "A. Alejo-Armijo and Parola, {A. Jorge} and Fernando Pina",
note = "info:eu-repo/grantAgreement/FCT/3599-PPCDT/127013/PT# This work was supported by the Associate Laboratory for Green Chemistry-LAQV, which is financed by national funds from FCT/MCTES (UID/QUI/50006/2019). FCT/MCTES is also acknowledged through the National Portuguese NMR Network RECI/BBB-BQB/0230/2012. A.A.-A. is grateful for the postdoctoral fellowship from Fundacion Alfonso Marti0n Escudero.",
year = "2019",
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AU - Alejo-Armijo, A.

AU - Parola, A. Jorge

AU - Pina, Fernando

N1 - info:eu-repo/grantAgreement/FCT/3599-PPCDT/127013/PT# This work was supported by the Associate Laboratory for Green Chemistry-LAQV, which is financed by national funds from FCT/MCTES (UID/QUI/50006/2019). FCT/MCTES is also acknowledged through the National Portuguese NMR Network RECI/BBB-BQB/0230/2012. A.A.-A. is grateful for the postdoctoral fellowship from Fundacion Alfonso Marti0n Escudero.

PY - 2019/2/22

Y1 - 2019/2/22

N2 - The multistate of chemical species generated by 4′-hydroxy-3,2′-furanoflavylium is similar to that of anthocyanins and related compounds. This furanoflavylium multistate system was fully characterized by UV-visible and NMR spectroscopy, allowing determination of the respective equilibrium and rate constants. In contrast to the multistate generated by flavylium cations derived from anthocyanins and related compounds, the furanoflavylium multistate is characterized by much slower hydration and tautomerization (pyran ring opening-closing). In addition, the cis-trans isomerization of the chalcones of this system (2′-hydroxyaurones) is extremely slow when compared with anthocyanins. The observed similar order of magnitude for tautomerization and isomerization rate constants leads to peculiar kinetics from the flavylium cation (pH = 1) to the stable trans-chalcone (higher pH values). The hemiketal appears and disappears during the first stages of the kinetics, which gives the intermediate cis-chalcone (pseudo-equilibrium). This last species disappears in a much slower process, as fully characterized by 1 H NMR, to give the final trans-chalcone.

AB - The multistate of chemical species generated by 4′-hydroxy-3,2′-furanoflavylium is similar to that of anthocyanins and related compounds. This furanoflavylium multistate system was fully characterized by UV-visible and NMR spectroscopy, allowing determination of the respective equilibrium and rate constants. In contrast to the multistate generated by flavylium cations derived from anthocyanins and related compounds, the furanoflavylium multistate is characterized by much slower hydration and tautomerization (pyran ring opening-closing). In addition, the cis-trans isomerization of the chalcones of this system (2′-hydroxyaurones) is extremely slow when compared with anthocyanins. The observed similar order of magnitude for tautomerization and isomerization rate constants leads to peculiar kinetics from the flavylium cation (pH = 1) to the stable trans-chalcone (higher pH values). The hemiketal appears and disappears during the first stages of the kinetics, which gives the intermediate cis-chalcone (pseudo-equilibrium). This last species disappears in a much slower process, as fully characterized by 1 H NMR, to give the final trans-chalcone.

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