Antimicrobial and antioxidant effects of a hydroxypyridinone derivative containing an oxime ether moiety and its application in shrimp preservation

In order to explore the potential of a novel tyrosinase inhibitor, namely the hydroxypyridinone derivative (5-hydroxy-1-octyl-4-oxo-1,4-dihydropyridine-2-carbaldehyde O-ethyl oxime, HPO), for shrimp preservation, six bacterial isolates from shrimp (Penaeus vannamei) (S1, S2, S3, S5, S6 and S7) were investigated. These bacteria were identified as Shewanella amazonensis, Shewanella haliotis, Microbacterium oxydans, Photobacterium damselae, Staphylococcus haemolyticus and Bacillus cereus. The antimicrobial effect of HPO on these bacteria was evaluated by an inhibition zone test, together with minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) assays. The results indicated that HPO possessed a stronger inhibitory effect than kojic acid. The antioxidant activity of HPO was evaluated by determining its 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide anion radical scavenging ability. The preservation effect on shrimp (Penaeus vannamei) of HPO was assessed by determining the quality indicators of the shrimp during the storage, including total bacterial count, pH value, total basic volatile nitrogen content, thiobarbituric acid reactive substances (TBARS) and by sensory evaluation. It was found that treatment of shrimp with HPO effectively extended the shelf life to 10 days at 4 °C. In the same assay, the shelf life of shrimps treated with 4-hexylresorcinol, kojic acid, and the control group was found to be 10, 6, and 4 days, respectively. The treatment of shrimps with HPO in combination with 0.1% citric acid further extended its shelf life to 12 days. Clearly, HPO could be applied as a shrimp preservative due to its potent anti-browning, antimicrobial and antioxidant activities.