Synthesis, characterization and antifungal efficacy of chitosan derivatives with triple quaternary ammonium groups

A novel type of water soluble chitosan derivatives (TQCSPX) were synthesized including 3-aminopyridine (TQCSP1) and 3-Amino-4-methylpyridine (TQCSP2). The theoretical structures of TQCSPX were calculated by Gaussian 09 and confirmed by FT-IR, 1 H NMR, 13 C NMR, elemental analysis and XRD. The antifungal properties of TQCSPX against Phytophthora capsici ( P. capsici ), Rhizoctonia solani ( R. solani ), Fusarium oxysporum ( F. oxysporum ) and Fusarium solani ( F. solani ) were evaluated at concentrations ranging from 0.2   mg/mL to 0.8   mg/mL. Antifungal results indicated that the derivatives have significantly enhanced antifungal activity after quaternized compared with the original chitosan (CS). Moreover, TQCSP1 inhibited the growth of P. capsici with inhibitory indices of 91.94% at 0.8   mg/mL. The experimental results demonstrated that the increasing number of the positive charge would improve the antifungal efficiency of chitosan, which may provide a novel direction for the development of fungicides.