Functionalized polysaccharides with aminoguaiacol: a competition between associative behavior and antibacterial and antioxidant activities

Abstract

Abstract In a previous study, we presented the development of a series of functionalized carboxymethylpullulan (CMP) grafted with aminoguaiacol (derivative of guaiacol with known antibacterial and antioxidant activities) leading to CMP-G derivatives with various degrees of substitution [DS(Ga)] from 0.16 to 0.58. Our results have shown the efficiency of the grafting both with the evidence of antioxidant and antibacterial activities (Staphylococcus aureus) of the CMP-G derivatives. Nevertheless, an important result has shown surprisingly that such biological activity was not clearly improved with the DS(Ga) unlike the antioxidant activity. These results were probably correlated with a peculiar associative behavior of the derivative (i.e. amphiphilic character) due to the grafted hydrophobic guaiacol groups leading to preferential intramolecular association which was particularly important in the more concentrated regime (polysoap behavior). To complete this study, we propose here two strategies in order to diminish the associative character and notably the polysoap behavior: (i) decrease the DS(Ga) of CMP derivative with a CMP-G0.05 [grafted with a DS(Ga) = 0.05], (ii) conduct the functionalization onto a more rigid polysaccharide backbone as alginate. Our results show a good correlation of the associative physicochemical behaviors with both antioxidant and antibacterial activities. They also confirm the availability of these strategies mainly for the first one (i.e. CMP-G0.05). The main result indicates that the lower is the DS(Ga), the better is the antibacterial activity thanks to a lower associative character. Finally, this study also shows that the grafting of aminoguaiacol is possible onto another anionic polysaccharide (i.e. alginate).