Antifungal properties and preservation applications of resin acid modified chitosan derivatives

Abstract

In order to obtain natural bio-antimicrobial agents with better antifungal activity, the present study compared the antifungal properties of different structural natural resin acid derivatives (dehydroabietic acid (DHA), acrylpimaric acid (APA), and maleopimaric anhydride (MPA)) grafted with chitosan C₂-OH and investigated the relationship between structure and activity. The structures of the derivatives were determined by FTIR and ¹H NMR. The antifungal properties were determined by mycelial growth rate method. The results demonstrated that CS-DHA (CSDA) exhibited the capacity to inhibit the majority of the tested fungi with notable efficacy, with an optimal antifungal effect observed at 97.53% against Alternaria solani. CS-APA (CSAA) demonstrated a comparatively weaker antifungal effect in comparison to CSDA, yet it exhibited a stronger effect when compared to CS-MPA (CSMA). SEM, TEM and relative permeability of cell membranes proved that the derivatives inhibited fungal growth by destroying the cell wall structure. The in vivo experiments proved that the derivatives all have the effect of protecting chili peppers, which has some application prospects. The best curative effect of CSAA on chili was observed at 1.5 mg/mL concentration (21.04%). At 3 mg/mL concentration, CSDA showed the best protective effect (29.48%) against chili peppers, which was closest to the effect of Imazalil at the same concentration. Meanwhile, the three derivatives had good preservation effect on cherry tomatoes, and the longest one could extend the shelf life by 6 days.