Preparation, characterization, and antifungal evaluation of a new type of aminourea chitooligosaccharide derivatives

Abstract

Phytopathogenic fungi cause heavy negative impact on the agricultural economy, but most existing fungicides are toxic and pose a threat to both human health and environments. A green and efficient fungicide is urgently needed. Chitooligosaccharides (COSs), the degradation products of natural polysaccharide chitosan, are nontoxic and biodegradable antifungal substances. In this study, a novel type of aminourea chitooligosaccharide derivatives (AUCOS) was synthesized by successively grafting a hydrazine group and an amine-carbonyl group onto a chitooligosaccharide backbone to enhance the antifungal capability of COSs. The structures of the target compounds were identified by FTIR, 1 H NMR, and 13 C NMR, and the degree of substitution of each product was calculated from the results of the elemental analysis. The antifungal activities of the prepared chitooligosaccharide derivatives against Fusarium solani, Verticillium albo-atrum and Phytophthora capsici were tested in vitro. The AUCOSs had better inhibitory efficiencies against the three plant pathogen fungi than that of chitooligosaccharide, of which aminourea chitooligosaccharide 2 (AUCOS2) was the most promising antifungal compound, whose highest inhibition rates were 60.12%, 82.95%, and 85.23% against F. solani, V. albo-atrum and P. capsici, respectively. The synthesized derivatives have good application prospects in crop protection and deserve further research.