Modification of pectin with UV-absorbing substitutents and its effect on the structural and hydrodynamic properties of the water-soluble derivatives

Gordon A. Morris, Zdenka Hromádková, Anna Ebringerová, Anna Malovíková, Juraj Alföldi, Stephen E. Harding

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Citrus pectin with a low degree of methyl esterification (LMP) and its deesterified form, potassium pectate (KP), were modified with a low amount of UV-absorbing substituents. For this purpose, two different substitution reactions were used (a) alkylation of hydroxyl groups with p-carboxybenzyl bromide in aqueous alkali and (b) alkylation of the carboxylate group with benzyl bromide in the DMSO/TBAI/catalyst system. Chemical and spectroscopic methods reveal a low degree of substitution (DS<0.1) for the derivatives. The hydrodynamic properties were assessed by analytical ultracentrifugion, viscometry, and HPGPC. The results indicate that the introduction of small amounts of p-carboxybenzyl ether groups practically had no effect on the hydrodynamic properties in the case of KP, whereas, it was accompanied with a decrease of the molecular mass for LMP. The degradation was more pronounced during the benzyl esterification of LMP. The results confirmed that LMP is susceptible to chain cleavage due to β-elimination during both modification reactions. However, KP seems to be more tolerant of the reaction conditions.

LanguageEnglish
Pages351-359
Number of pages9
JournalCarbohydrate Polymers
Volume48
Issue number4
Early online date18 Feb 2002
DOIs
Publication statusPublished - 1 Jun 2002
Externally publishedYes

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alkylation
Esterification
Alkylation
esterification
Hydrodynamics
bromides
pectins
hydrodynamics
Substitution reactions
chemical derivatives
viscometry
Derivatives
Water
Viscosity measurement
Molecular mass
Alkalies
Dimethyl Sulfoxide
Bromides
catalysts
alkalis

Cite this

Morris, Gordon A. ; Hromádková, Zdenka ; Ebringerová, Anna ; Malovíková, Anna ; Alföldi, Juraj ; Harding, Stephen E. / Modification of pectin with UV-absorbing substitutents and its effect on the structural and hydrodynamic properties of the water-soluble derivatives. In: Carbohydrate Polymers. 2002 ; Vol. 48, No. 4. pp. 351-359.
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Modification of pectin with UV-absorbing substitutents and its effect on the structural and hydrodynamic properties of the water-soluble derivatives. / Morris, Gordon A.; Hromádková, Zdenka; Ebringerová, Anna; Malovíková, Anna; Alföldi, Juraj; Harding, Stephen E.

In: Carbohydrate Polymers, Vol. 48, No. 4, 01.06.2002, p. 351-359.

Research output: Contribution to journalArticle

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N2 - Citrus pectin with a low degree of methyl esterification (LMP) and its deesterified form, potassium pectate (KP), were modified with a low amount of UV-absorbing substituents. For this purpose, two different substitution reactions were used (a) alkylation of hydroxyl groups with p-carboxybenzyl bromide in aqueous alkali and (b) alkylation of the carboxylate group with benzyl bromide in the DMSO/TBAI/catalyst system. Chemical and spectroscopic methods reveal a low degree of substitution (DS<0.1) for the derivatives. The hydrodynamic properties were assessed by analytical ultracentrifugion, viscometry, and HPGPC. The results indicate that the introduction of small amounts of p-carboxybenzyl ether groups practically had no effect on the hydrodynamic properties in the case of KP, whereas, it was accompanied with a decrease of the molecular mass for LMP. The degradation was more pronounced during the benzyl esterification of LMP. The results confirmed that LMP is susceptible to chain cleavage due to β-elimination during both modification reactions. However, KP seems to be more tolerant of the reaction conditions.

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