Synthesis, characterization, and antifungal property of starch derivatives modified with quaternary phosphonium salts

Four novel starch derivatives modified with quaternary phosphonium salts were designed and successfully synthesized, including trimethylphosphonium acetyl starch chloride, tributylphosphonium acetyl starch chloride, tricyclohexylphosphonium acetyl starch chloride, triphenylphosphonium acetyl starch chloride, and characterized by FTIR, UV, H-1 NMR, C-13 NMR, and P-31 NMR spectra. Their antifungal activities against four kinds of phytopathogens were evaluated using the radial growth assay and minimum inhibitory concentration procedure. The fungicidal assessment revealed that the synthesized starch derivatives had superior antifungal activity compared with starch. Especially, the inhibitory indices of triphenylphosphonium acetyl starch chloride against these four kinds of plant pathogens were higher than 70% at 1.0 mg/mL. The results indicated that quaternary phosphonium groups should be high-efficiency antifungal function groups, and meanwhile longer alkyl chain lengths or the stronger electron-withdrawing groups were responsible for enhanced antifungal versatility and efficacy. The cytotoxicity of starch and starch derivatives bearing quaternary phosphonium salts was evaluated in vitro on HEK-293T cells. As novel quaternary phosphoniuni functionalized starch derivatives could be prepared efficiently and exhibited superduper antifungal activity, this synthetic strategy might provide an effective way and notion to prepare novel antifungal biomaterials. (C) 2017 Published by Elsevier B.V.