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Determination of acidity constants of curcumin in aqueous solution and apparent rate constant of its decomposition

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Title: Determination of acidity constants of curcumin in aqueous solution and apparent rate constant of its decomposition
Authors: Bernabé-Pineda, Margarita1, Ramírez-Silva, María Teresa1, Romero-Romo, Mario2, González-Vergara, Enrique3, Rojas-Hernández, Alberto1 suemi918@xanum.uam.mx
Source: Spectrochimica Acta Part A: Molecular & Biomolecular Spectroscopy. Apr2004, Vol. 60 Issue 5, p1091. 7p.
Subjects: Stability (Mechanics), Chemicals, Hydrogen-ion concentration, Acids, Chemical reactions
Abstract: The stability of curcumin (H3Cur) in aqueous media is improved when the systems in which it is present are at high pH values (higher than 11.7), fitting a model describable by a pseudo-zero order with a rate constant k′ for the disappearance of the Cur3− species of 1.39 (10−9) M min−1. There were three acidity constants measured for the curcumin as follows: pKA3=10.51±0.01 corresponding to the equilibrium HCur2−=Cur3−+H+, a pKA2=9.88±0.02 corresponding to the equilibrium H2Cur−=HCur−2+H+. These pKA values were attributed to the hydrogen of the phenol part of the curcumin, while the pKA1=8.38±0.04 corresponds to the equilibrium H3Cur=H2Cur−+H+ and is attributed the acetylacetone type group. Formation of quinoid structures play an important role in the tautomeric forms of the curcumin in aqueous media, which makes the experimental values differ from the theoretically calculated ones, depending on the conditions adopted in the study. [Copyright &y& Elsevier]
Copyright of Spectrochimica Acta Part A: Molecular & Biomolecular Spectroscopy is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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Items – Name: Title
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  Data: Determination of acidity constants of curcumin in aqueous solution and apparent rate constant of its decomposition
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  Data: <searchLink fieldCode="AR" term="%22Bernabé-Pineda%2C+Margarita%22">Bernabé-Pineda, Margarita</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Ramírez-Silva%2C+María+Teresa%22">Ramírez-Silva, María Teresa</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Romero-Romo%2C+Mario%22">Romero-Romo, Mario</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22González-Vergara%2C+Enrique%22">González-Vergara, Enrique</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Rojas-Hernández%2C+Alberto%22">Rojas-Hernández, Alberto</searchLink><relatesTo>1</relatesTo><i> suemi918@xanum.uam.mx</i>
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  Data: <searchLink fieldCode="JN" term="%22Spectrochimica+Acta+Part+A%3A+Molecular+%26+Biomolecular+Spectroscopy%22">Spectrochimica Acta Part A: Molecular & Biomolecular Spectroscopy</searchLink>. Apr2004, Vol. 60 Issue 5, p1091. 7p.
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  Data: <searchLink fieldCode="DE" term="%22Stability+%28Mechanics%29%22">Stability (Mechanics)</searchLink><br /><searchLink fieldCode="DE" term="%22Chemicals%22">Chemicals</searchLink><br /><searchLink fieldCode="DE" term="%22Hydrogen-ion+concentration%22">Hydrogen-ion concentration</searchLink><br /><searchLink fieldCode="DE" term="%22Acids%22">Acids</searchLink><br /><searchLink fieldCode="DE" term="%22Chemical+reactions%22">Chemical reactions</searchLink>
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  Data: The stability of curcumin (H3Cur) in aqueous media is improved when the systems in which it is present are at high pH values (higher than 11.7), fitting a model describable by a pseudo-zero order with a rate constant k′ for the disappearance of the Cur3− species of 1.39 (10−9) M min−1. There were three acidity constants measured for the curcumin as follows: <F>pKA3=10.51±0.01</F> corresponding to the equilibrium <F>HCur2−=Cur3−+H+</F>, a <F>pKA2=9.88±0.02</F> corresponding to the equilibrium <F>H2Cur−=HCur−2+H+</F>. These pKA values were attributed to the hydrogen of the phenol part of the curcumin, while the <F>pKA1=8.38±0.04</F> corresponds to the equilibrium <F>H3Cur=H2Cur−+H+</F> and is attributed the acetylacetone type group. Formation of quinoid structures play an important role in the tautomeric forms of the curcumin in aqueous media, which makes the experimental values differ from the theoretically calculated ones, depending on the conditions adopted in the study. [Copyright &y& Elsevier]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Spectrochimica Acta Part A: Molecular & Biomolecular Spectroscopy is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1016/S1386-1425(03)00342-1
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      – Code: eng
        Text: English
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      – SubjectFull: Stability (Mechanics)
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      – SubjectFull: Chemicals
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      – SubjectFull: Hydrogen-ion concentration
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      – SubjectFull: Acids
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      – SubjectFull: Chemical reactions
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      – TitleFull: Determination of acidity constants of curcumin in aqueous solution and apparent rate constant of its decomposition
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            NameFull: Bernabé-Pineda, Margarita
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            NameFull: Ramírez-Silva, María Teresa
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            NameFull: González-Vergara, Enrique
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            NameFull: Rojas-Hernández, Alberto
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              M: 04
              Text: Apr2004
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              Y: 2004
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