Antibacterial activity of methylated chitosan and chitooligomer derivatives: Synthesis and structure activity relationships

Ögmundur Vidar Rúnarsson, Jukka Holappa, Tapio Nevalainen, Martha Hjálmarsdóttir, Tomi Järvinen, Thorsteinn Loftsson, Jón M. Einarsson, Sigrídur Jónsdóttir, Margrét Valdimarsdóttir, Már Másson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

127 Citations (Scopus)


The purpose of this study was to synthesize series of methylated chitosaccharide derivatives, possessing various degree of methylation, and to determine their structure activity relationship (SAR) with regard to their antibacterial effect against Staphylococcus aureus. Chitosan polymer and chitooligomers were used as starting materials and were methylated by reaction with methyl iodide. Depending on the reaction conditions the degree of N-quaternization ranged from 0% to 74%, with varying degree of N,N-dimethylation, N-monomethylation and O-methylation. More selective N-quaternization could be obtained with protection group strategy. At pH 5.5 the chitosaccharide polymers and their methylated derivatives were active against S. aureus with minimal inhibitory concentration (MIC) ranging from 16 to 512 μg/mL. At pH 7.2 the non-quaternized derivatives were inactive but their highly N-quaternized derivatives showed MIC as low as 8 μg/mL. The chitooligomers, as well as their derivatives, were inactive at both pH's. The SAR studies revealed that N-quaternization was mainly responsible for the antibacterial effects at pH 7.2, whereas it did not contribute to the antibacterial activity under acidic conditions.

Original languageEnglish
Pages (from-to)2660-2671
Number of pages12
JournalEuropean Polymer Journal
Issue number6
Publication statusPublished - Jun 2007

Bibliographical note

Funding Information:
Financial support from The Iceland Research Council, University of Iceland Research Fund and Academy of Finland is gratefully acknowledged.

Other keywords

  • Antibacterial activity
  • Chitosan
  • Quaternary chitosan
  • Structure activity
  • Trimethylated chitosan


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