Preparation of cationic chitooligosaccharide derivatives bearing N-halogenated benzyl pyridinium and assessment of their antimicrobial activities

As one of the most promising and eco-friendly oligosaccharides with a variety of potential biological activities, chitooligosaccharide has attracted much attention because of its unique properties. The modification of chitooligosaccharide has been used for synthesizing novel chitooligosaccharide derivatives with excellent antimicrobial activities. In this work, chitooligosaccharide-niacin acid conjugate was firstly synthesized by using N,N & PRIME;-carbonyldiimidazole as catalyst and its cationic derivatives were obtained by further nucleophilic reaction between chitooligosaccharide-niacin acid conjugate and halogenated benzyl bromide. The structural characteristics of chitooligosaccharide derivatives were investigated by FTIR and NMR. In addition, the antimicrobial property of three end products against three plant-threatening fungal pathogens and four harmful bacteria was evaluated by the disc diffusion method. The in vitro antimicrobial activities results presented a significantly improved inhibition capability against pathogenic microorganisms of cationic chitooligosaccharide derivatives bearing N-halogenated benzyl pyridinium as compared to chitooligosaccharide and chitooligosaccharide-niacin acid conjugate. Specifically, all end products possessed significant enhancement in antimicrobial activities, the inhibition zones of the derivatives were from 6.3 to 19.4 mm against fungi and compounds also had excellent bacteriostatic activity (7.7-20.8 mm). Specially, chitooligosaccharide derivative bearing 4-chlorobenzyl showed the strongest antifungal activity, its inhibition zone reached up to 19.4 mm against F. oxysporum, which was close to the carbendazim (22.3 mm), it also showed excellent antibacterial activity against harmful bacterial, its bacteriostatic diameter was astonishingly 20.8 mm. These data indicated that the introduction of pyridinium salt with halogenated benzyl by the reaction of halogenated benzyl bromide groups and chitooligosaccharide-niacin acid conjugate could conspicuously enhance the antimicrobial effect. Chitooligosaccharide derivatives with enhanced antimicrobial activities could serve as potential biomaterial for antimicrobial applications.

Automated summary

In this study, chitooligosaccharide derivatives with excellent antimicrobial activities were synthesized and their inhibitory effects on pathogenic microorganisms were evaluated, demonstrating significantly improved antimicrobial capabilities.