Functionalization of chitosan by a free radical reaction: Characterization, antioxidant and antibacterial potential

Abstract

Chitosan was functionalized with epigallocatechin gallate (EGCG) by a free radical-induced grafting procedure, which was carried out by a redox pair (ascorbic acid/hydrogen peroxide) as the radical initiator. The successful preparation of EGCG grafted-chitosan was verified by spectroscopic (UV, FTIR and XPS) and thermal (DSC and TGA) analyses. The degree of grafting of phenolic compounds onto the chitosan was determined by the Folin-Ciocalteu procedure. Additionally, the biological activities (antioxidant and antibacterial) of pure EGCG, blank chitosan and EGCG grafted-chitosan were evaluated. The spectroscopic and thermal results indicate chitosan functionalization with EGCG; the EGCG content was 25.8mg/g of EGCG grafted-chitosan. The antibacterial activity of the EGCG grafted-chitosan was increased compared to pure EGCG or blank chitosan against S. aureus and Pseudomonas sp. (p<0.05). Additionally, EGCG grafted-chitosan showed higher antioxidant activity than blank chitosan. These results indicate that EGCG grafted-chitosan might be useful in active food packaging.

Keywords: 2,2-Diphenyl-1-picrylhydrazyl radical (DPPH) (PubChem CID: 74358); 2,2′-Azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) (PubChem CID: 5815211); 6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) (PubChem CID: 40634); Acetic acid (PubChem CID: 176); Antibacterial; Antioxidant; Ascorbic acid (PubChem CID: 54670067); Chitosan (PubChem CID: 71853); Epigallocatechin gallate; Epigallocatechin gallate (EGCG) (PubChem CID: 44134699); Folin-Ciocalteu reagent (PubChem CID: 452323); Grafting; Hydrogen peroxide (H(2)O(2)) (PubChem CID: 784); Modified chitosan; Sodium carbonate (PubChem CID: 10340).