Modified chitosan with different phenolic acids: Characterization, physicochemical properties, and biological activity.

[Display omitted] • Phenolic acids were grafted onto chitosan by carbodiimide coupling method. • The properties of copolymers were related to the type of phenolic acid. • Antioxidant, antimicrobial activity and characteristic of conjugates were compared. • Chitosan conjugates exhibited strong biological activity than chitosan. • Chitosan conjugates reduced microbial growth and extended the shelf-life of seabass. This study synthesized five phenolic acid-chitosan copolymers utilizing the carbodiimide-mediated chemical crosslinking reaction. Comprehensive evaluations were conducted on their structural attributes, physicochemical properties, and biological activities. Fourier transform infrared confirmed successful grafting of phenolic acids onto chitosan via amide linkages. Additionally, ultraviolet–visible absorption spectroscopy and proton nuclear magnetic resonance analyses revealed novel absorption peaks between 200 and 400 nm and 6.0–8.0 ppm, respectively, attributable to the incorporated phenolic acids. Notably, the chitosan-gentisate acid copolymer exhibited significantly enhanced biological activity (p < 0.05) compared to pure chitosan and the other four conjugates, attributed to its highest grafting degree of approximately 295.93 mg/g. These modified chitosan derivatives effectively preserved the quality of sea bass (Lateolabrax japonicus) during refrigerated storage, extending its shelf-life by up to 9 days, 7 days, and 4 days relative to control, chitosan, and gentisate acid groups. [ABSTRACT FROM AUTHOR]