Novel Multifunctional Hydroxypyridinone Derivatives as Potential Shrimp Preservatives

In order to develop a new efficient method for the prolongation of shrimp shelf life, two novel hydroxypyridinone derivatives ((S)-2-amino-N-((S)-1-(((5-hydroxy-4-oxo-1,4-dihydropyridin-2-yl)methyl)amino)-1-oxo-3-phenylpropan-2-yl)-3-phenylpropanamide (2) and (S)-(5-hydroxy-4-oxo-1,4-dihydropyridin-2-yl)methyl 2-(benzyloxycarbonyl)-3- phenylpropanoate (3)) possessing strong tyrosinase inhibitory activity were investigated to explore their potential as shrimp preservatives. Their antimicrobial activities were evaluated by a disk diffusion method. Inhibition zone assays indicated that both 2 and 3 possess a stronger inhibitory effect than kojic acid. The minimum inhibition concentrations (MICs) of compound 3 against Bacillus subtilis, Staphylococcous aureus, Escherichia coli, Salmonella spp., and Pseudomonas aeruginosa were determined to be 32, 32, 32, 8, and 16 μg/mL. Both 2 and 3 were also found to possess antioxidant activity. The IC50 values of 2 and 3 for scavenging DPPH radical were measured to be 2.93 and 2.37 mg/mL, respectively. At 4 mg/mL, 2 and 3 were determined to have total antioxidant capacity of 2.43 and 2.72 U/mL, respectively. Compound 3 was further investigated for efficacy in shrimp preservation by sensory evaluation, determination of total volatile basic nitrogen (TVB-N), pH, and total bacterial count. The treatment with 3 was found to extend the shelf life of Penaeus vannamei Boone to 10 days at 4 °C, while the shelf life of shrimp treated with 4-hexylresorcinol, kojic acid, and the control group was 9, 6, and 4 days, respectively. Compound 3 could find application in the food industry, as a shrimp preservative, due to its protective properties.