Novel thiosemicarbazone chitosan derivatives: Preparation, characterization, and antifungal activity

Three novel thiosemicarbazone chitosan derivatives were obtained via condensation reaction of thiosemicarbazide chitosan with phenylaldehyde, o-hydroxyphenylaldehyde, and p-methoxyphenylaldehyde, respectively. Antifungal activity against the common crop-threatening pathogenic fungi Stemphylium solani weber (S. solani), Rhizoctonia solani Kühn (R. solani), Alternaria solani (A. solani), and Phomopsis asparagi (Sacc.) (P. asparagi) was tested in vitro at 0.05, 0.1, and 0.5 mg/mL. The derivatives had broad-spectrum antifungal activity that was greatly enhanced in comparison with chitosan. In fact, the highest antifungal index reached 100%. At 0.05 mg/mL, the o-hydroxyphenylaldehyde thiosemicarbazone chitosan inhibited growth of R. solani at 52.6%, and was stronger than polyoxin whose antifungal index was found to be 31.5%. The chitosan derivatives described here lend themselves to future applicative studies in agriculture.