Novel chitooligosaccharide derivatives modified with halogenated curcumin: Synthesis, characterization, and application for photodynamic inactivation preservation

To improve the water solubility and photodynamic inactivation (PDI) activity of curcumin (Cur), three novel chitooligosaccharide derivatives, COS-N-XCur (X = F, Cl, or Br), modified with halogenated curcumin were synthesized via nucleophilic substitution reactions. The results revealed that, owing to the absence of molecular aggregation, COS-N-FCur exhibited the highest singlet oxygen (¹O₂) generation capability (capture agent method), reaching 78.52 %. The COS-N-FCur-mediated PDI of large yellow croaker (Larimichthys crocea) demonstrated the highest sensory acceptability and the best color stability after 8 days of storage at 4 °C. At the end of the storage period, the pH, total bacterial count, and total volatile basic nitrogen (TVB-N) content of the treatment group showed the lowest values, indicating significant inhibitory effects (P < 0.05), with values of 7.02 ± 0.03, 6.23 ± 0.11 lg CFU/g, and 19.18 ± 0.37 mg/100 g, respectively. High-throughput sequencing analysis revealed that the microbial community diversity was significantly reduced after PDI treatment. Specifically, on the 8th day of storage, compared to the control group, the COS-N-FCur treatment group presented a significant reduction in Pseudomonas, with a decrease of 19.16 %. Furthermore, the COS-N-FCur had almost no cytotoxic effect on RAW264.7 cells, and the cell survival rate was 99.47 ± 0.22 % (COS-N-FCur concentration of 10 mmol/L). Therefore, the findings of this study provide important insights into the preparation of photosensitizers with high photosensitive activity and PDI preservation in aquatic products.