Relevance of molecular weight of chitosan-N-2-hydroxypropyl trimethyl ammonium chloride and their antioxidant activities.

The antioxidant potency of high/low molecular weight quaternary chitosan derivatives was investigated employing various established systems in vitro, such as superoxide (O*(2)(-)) and hydroxyl (*OH) radicals scavenging, reducing power and iron ion chelating. As expected, we obtained several satisfying results, as follow: firstly, low molecular weight quaternary chitosan had stronger scavenging effect on O*(2)(-) and *OH than high molecular weight quaternary chitosan. Secondly, the reducing power of low molecular weight quaternary chitosan was more pronounced than that of high molecular weight quaternary chitosan. Thirdly, ferrous ion chelating potency were showed to increase first and decrease afterwards with increasing concentration for two kinds of quaternary chitosans, namely, they have not concentration-dependence. However, the scavenging rate and reducing power of high and low molecular weight quaternary chitosans increased with their increasing concentrations, and hence were concentration-dependent.