Synthesis, Characterization, and Antifungal Activity of Pyridine-Based Triple Quaternized Chitosan Derivatives.

In this study, a series of triple quaternized chitosan derivatives, including 6- O -[(2-hydroxy-3-trimethylammonium)propyl]-2- N -(1-pyridylmethyl-2-ylmethyl)- N , N -dimethyl chitosan chloride ( 7 ), 6- O -[(2-hydroxy-3-trimethylammonium)propyl]-2- N -(1-pyridylmethyl-3-yl- methyl)- N , N -dimethyl chitosan chloride ( 8 ), and 6- O -[(2-hydroxy-3-trimethylammonium)propyl]- 2- N -(1-pyridylmethyl-4-ylmethyl)- N , N -dimethyl chitosan chloride ( 9 ) were successfully designed and synthesized via reacting epoxypropyl trimethylammonium chloride with the N -pyridinium double quaternized chitosan derivatives. Detailed structural characterization was carried out using FT-IR and ¹H-NMR spectroscopy, and elemental analysis. Besides, the activity of the triple quaternized chitosan derivatives against three common plant pathogenic fungi, Watermelon fusarium , Fusarium oxysporum , and Phomopsis asparagi , was investigated in vitro. The results indicated that the triple quaternized chitosan derivatives had enhanced antifungal activity when compared to double quaternized chitosan derivatives and chitosan, especially at 1.0 mg/mL, which confirmed the theory that the higher density of positive charge contributed to the antifungal activity. Moreover, 8 with an almost 99% inhibitory index showed the better antifungal activity against Watermelon fusarium . Moreover, the cytotoxicity of the products was also evaluated in vitro on 3T3-L1 cells and all the triple quaternized chitosan derivatives exhibited low cytotoxicity. These results suggested that triple quaternized chitosan derivatives may be used as good antifungal biomaterials.