Synthesis of water soluble chitosan derivatives with halogeno-1,2,3-triazole and their antifungal activity

• Novel chitosan derivatives containing halogeno-1,2,3-triazole group are synthesized.
• The synthesized chitosan derivatives possess excellent antifungal activity and water solubility.
• The synergistic effect of halogens and triazole improve antifungal activity of chitosan derivatives.
• The electron-withdrawing capacity and biological activity could influence the antifungal activity of chitosan derivatives.

Chitosan is an abundant and renewable polysaccharide, which exhibits attractive bioactivities and natural properties. Improvement such as chemical modification of chitosan is often performed prior to further utilization. Three novel water soluble chitosan derivatives containing 1,2,3- triazole with or without halogen was designed and synthesized. Their antifungal activity against three kinds of phytopathogens was estimated by hyphal measurement in vitro. The inhibitory property and water solubility of the synthesized chitosan derivatives exhibited a remarkable improvement over chitosan. It is hypothesized that thiazolyl groups enable the synthesized chitosan to possess obviously better antifungal activity. Moreover, CTCTS and BTCTS, which have halogens at the periphery of polymers, inhibited the growth of tested phytopathogens more effectively with inhibitory indices of 81–93% at 1.0 mg/mL. The halogens could have a synergistic effect with triazole as they exhibited antifungal activity and electron-withdrawing capacity, which improve the antifungal activity of chitosan derivatives.