Chitooligosaccharides: Synthesis, Characterization and Applications

Polymer Science Series A (Impact Factor: 0.92). 07/2011; 53(7):583-612. DOI: 10.1134/S0965545X11070066

ABSTRACT Chitosans with high degree of polymerization and molecular weight exhibit poor aqueous solubility which is an impediment in
their applicability. The low molecular weight chitosans (LMWCs) and chitooligosaccharides (COSs) can be used to avoid this
hurdle. The development of an efficient process for reducing the molecular weight of chitosan, without altering its chemical
structure, is of great interest to produce tailormade chitosans of varying Degree of Acetylation (DAs) and Degree of Polymerization
(DPs). The production of well-defined COS-mixtures, or even pure COS, is of great interest since these oligosaccharides are
thought to have several interesting bioactivities and applications. For this proper delineation of their characteristics is
needed. Hence it is our attempt to provide an overview of difffernt methods and techniques of their production and characterization.
Several methods viz. depolymerization under the action of reagents, enzymes, high energy impact and combinations thereof have
been employed to get COS by depolymerization of high molecular weight chitosans. Acid hydrolysis (hydrochloric, nitrous, phosphoric
acid, hydrogen fluoride) and oxidative reductive depolymerization (mediated by peroxide, ozone, and persulfate) are important
routes for synthesis of COSs. These oligomers can be produced from chitin or chitosan as a starting material by enzymatic
conversions. For this, numbers of enzymes have been used. Depolymerization under high energy impact and recombinant approaches
are also being tried for production of COSs. LMWC and COS, like parent chitosan, can be used for drug delivery and gene delivery.
The efficient and productive processes are needed for separation of COSs into its components or mixture of defined characters.
The characterization of COS can be carried out by chromatographic and spectroscopic techniques. Importantly COSs display an
array of biological activities as antimicrobial, anticancer/antimetastatic, wound healing acceleration, immunostimulation,
apoptosis induction or inhibiton, antioxidant, enzyme inhibiton, antihyperlipidemic, antidiabetic, chemoprevention, and many
more. A few of the biological actions are reported only sporadically where as some are persistently taken up by the scientific
fraternity to substantiate the claims and propose possible mechanisms of action. However there remains the disagreement of
results on COS activities. The disagreements can arise due to poor and variable reporting of the properties of COS such as
used in the studies as molecular weight, degree of acetylation, molecular weight distribution, and the pattern of N-acetylation
etc. With production of COS of well defined characters it might be possible to understand the modes of actions of COS in better

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Available from: Nazma Inamdar, Feb 10, 2014
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    • "However, due to the complexity of controlling the progress of the reaction, these treatments also result in the formation of secondary compounds that are difficult to remove [75]. With hydrolysis by physical methods such as irradiation with low-frequency ultrasound (20 kHz), partial depolymerization is obtained, reducing the average MW from 2000 kDa down to 450 kDa or from 300 kDa to 50 kDa, but the reduction of molecular weight is limited [75]. "
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    ABSTRACT: Chitin is a natural polysaccharide of major importance. This biopolymer is synthesized by an enormous number of living organisms; considering the amount of chitin produced annually in the world, it is the most abundant polymer after cellulose. The most important derivative of chitin is chitosan, obtained by partial deacetylation of chitin under alkaline conditions or by enzymatic hydrolysis. Chitin and chitosan are known to have important functional activities but poor solubility makes them difficult to use in food and biomedicinal applications. Chitooligosaccharides (COS) are the degraded products of chitosan or chitin prepared by enzymatic or chemical hydrolysis of chitosan. The greater solubility and low viscosity of COS have attracted the interest of many researchers to utilize COS and their derivatives for various biomedical applications. In light of the recent interest in the biomedical applications of chitin, chitosan, and their derivatives, this review focuses on the preparation and biological activities of chitin, chitosan, COS, and their derivatives.
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