Chitosan oligosaccharide(COS)is a significant functional compound derived from shrimp and crab shells.COS has certain antifungal activity,but its antifungal activity is not strong.This study aimed to enhance the antifungal activity of COS by chemically modifying its hydroxyl groups using octanoyl chloride and decanoyl chloride.Two acylated derivatives of COS(COS-C8 and COS-C10)were synthesized,and their antifungal activities against Rhizoctonia Solani and Thanatephorus cucumeris were preliminarily investigated.Fourier-transform infrared spectroscopy revealed new absorption peaks at 1558 cm-1 and 1446 cm-1,indicating the introduction of carbonyl groups(C=O)on the COS.Nuclear magnetic resonance spectroscopy showed a distinct absorption peak at δ=0.86 ppm,attributed to the chemical shift of the methyl groups at the end of the acyl chain.X-ray diffraction spectra demonstrated that the maximum peak of the COS acylated derivatives shifted to 2θ=31.7°,confirming the successful synthesis of the COS acylated derivatives.The results of the antifungal assays indicated that COS acylated derivatives exhibited significant inhibitory effects within the tested concentration range,and the best antifungal performance was detected at the concentration of 2 mg/mL.The antifungal activity of COS derivatives against Rhizoctonia solani was superior to that of COS itself.This research provides theoretical support for the development of environmentally friendly antimicrobial agents.
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