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Modification of Pectin by Graft Copolymerization
The use of synthetic polymers for increasing the functionality of the polysaccharides is attracting great attention and has wide applications in immobilization of
enzymes, drug delivery systems and bioseparations. This can be easily achieved by
the process of graft copolymerization in which the pectin can be modified by using
ceric ammonium nitrate, N,N,N0,N0-tetramethylethylenediamine (TEMED) and
microwave-induced graft copolymerization of N,N-diethylacrylamide (Is¸õklan and
Tokmak 2018). The formulated graft polymers have low critical solution temperatures of 31 °C, high thermal resistivity, biocompatibility as a biomaterial and are
thermos-sensitive. Giacomazza et al. 2014 proposed that the development of a gelling system utilizing high esterified pectin and water-soluble maltose-conjugated
chitosan that can gel rapidly as a model for tissue engineering. The hydrophobic
modification of pectin involves the reaction of pectin with diacyl chlorides glutaryl
and sebacoyl chloride) which yields mono-grafted (isolated chains) and bi-grafted
(chemical gels) structures. The length of the carbon chains inserted as a result of
acylation have a underlying effect on the yield of mono-grafted and bi-grafted structures (Seslija et al. 2018). The heterogeneity of the modified pectin, depicted by the
entanglement of sticky polymer microparticles as compared to unmodified pectin is
more and is more liable to heat degradation. There is a reduction in the glass transition temperature with the increase in size of the acyl chains on the polymer backbone. There is an enhancement of the hydrophobicity of the pectin as a result of
acylation. The pectins modified with phenols are becoming more popular. The
structure of pectin has a good amount of ferulic acid units but its abundance is not
so high (Morris et al. 2010). When the enzymatic graft of the ferulic acid oxidation
products is carried on, the process usually takes place in aqueous medium via catalyzation using Myceliophthora thermophila laccase as the biocatalyst (Karaki
et al. 2017).
The reaction between the pectin and the ferulic acid oxidation products involves
the alteration of thermal and morphological properties. The hygroscopic behaviour
is less when the water activity is less than 0.5 and more when the water activity is
above 0.5. Also the viscosity of the feruloylated pectin is less and exhibits a different calcium-dependent gelation behaviour. The antioxidant properties also display a
significant improvement. Covalent bonds are found between the pectin carboxyl
groups and the laccase-mediated ferulic acid oxidation products. So modification of
pectin using phenols can help to achieve pectins with various properties of interest.
Modification of Pectin by Thiolation
Thiolated pectin from citrus has been obtained with thioglycolic acid and has been
reported to be as a potent mucoadhesive delivery system for metformin (Sharma and
Ahuja 2011).Similarly the use of thiolated lemon pectin for buccal delivery of drugs
has also been reported by (Hauptstein et al. 2014).The modification in such cases
takes place by conjugation of cysteine through the formation of amide bonds. In this
Pectin
Modification of Pectin by Graft Copolymerization
The use of synthetic polymers for increasing the functionality of the polysaccharides is attracting great attention and has wide applications in immobilization of
enzymes, drug delivery systems and bioseparations. This can be easily achieved by
the process of graft copolymerization in which the pectin can be modified by using
ceric ammonium nitrate, N,N,N0,N0-tetramethylethylenediamine (TEMED) and
microwave-induced graft copolymerization of N,N-diethylacrylamide (Is¸õklan and
Tokmak 2018). The formulated graft polymers have low critical solution temperatures of 31 °C, high thermal resistivity, biocompatibility as a biomaterial and are
thermos-sensitive. Giacomazza et al. 2014 proposed that the development of a gelling system utilizing high esterified pectin and water-soluble maltose-conjugated
chitosan that can gel rapidly as a model for tissue engineering. The hydrophobic
modification of pectin involves the reaction of pectin with diacyl chlorides glutaryl
and sebacoyl chloride) which yields mono-grafted (isolated chains) and bi-grafted
(chemical gels) structures. The length of the carbon chains inserted as a result of
acylation have a underlying effect on the yield of mono-grafted and bi-grafted structures (Seslija et al. 2018). The heterogeneity of the modified pectin, depicted by the
entanglement of sticky polymer microparticles as compared to unmodified pectin is
more and is more liable to heat degradation. There is a reduction in the glass transition temperature with the increase in size of the acyl chains on the polymer backbone. There is an enhancement of the hydrophobicity of the pectin as a result of
acylation. The pectins modified with phenols are becoming more popular. The
structure of pectin has a good amount of ferulic acid units but its abundance is not
so high (Morris et al. 2010). When the enzymatic graft of the ferulic acid oxidation
products is carried on, the process usually takes place in aqueous medium via catalyzation using Myceliophthora thermophila laccase as the biocatalyst (Karaki
et al. 2017).
The reaction between the pectin and the ferulic acid oxidation products involves
the alteration of thermal and morphological properties. The hygroscopic behaviour
is less when the water activity is less than 0.5 and more when the water activity is
above 0.5. Also the viscosity of the feruloylated pectin is less and exhibits a different calcium-dependent gelation behaviour. The antioxidant properties also display a
significant improvement. Covalent bonds are found between the pectin carboxyl
groups and the laccase-mediated ferulic acid oxidation products. So modification of
pectin using phenols can help to achieve pectins with various properties of interest.
Modification of Pectin by Thiolation
Thiolated pectin from citrus has been obtained with thioglycolic acid and has been
reported to be as a potent mucoadhesive delivery system for metformin (Sharma and
Ahuja 2011).Similarly the use of thiolated lemon pectin for buccal delivery of drugs
has also been reported by (Hauptstein et al. 2014).The modification in such cases
takes place by conjugation of cysteine through the formation of amide bonds. In this
Pectin