3‐Hydroxypyridinone‐<scp>l</scp>‐phenylalanine conjugates with antimicrobial and tyrosinase inhibitory activities as potential shrimp preservatives

Abstract

Summary To explore the potential of novel tyrosinase inhibitors, 3‐hydroxypyridinone‐ l ‐phenylalanine conjugates, as shrimp preservatives, compounds 1 and 2 were evaluated for the antimicrobial activity, and compound 2 was investigated for the shrimp preservative efficacy. It was found that they both possess a stronger antibacterial effect than kojic acid against two Gram‐positive bacteria and three Gram‐negative bacteria. The minimum inhibitory concentrations (MICs) of compound 2 against E scherichia coli , S taphylococcous aureus , S almonella gallinarum , V ibrio parahaemolyticus and B acillus subtilis were determined as 18.5, 37, 148, 37 and 295 μg mL −1 , respectively, whereas MIC s of kojic acid against the same 5 bacterial strains were determined to be 355, 178, 1420, 1420 and 355 μg mL −1 , respectively. It has also been demonstrated that treatment with compound 2 improves the sensory properties, retards the growth of spoilage bacteria, decreases the total volatile basic nitrogen (TVB‐N) and increases the p H of P enaeus vannamei Boone, thereby extending the shelf life to 10 days. In contrast, the shelf life of shrimp treated with kojic acid and the control group was 7 and 6 days, respectively. Clearly, 3‐hydroxypyridinone‐ l ‐phenylalanine conjugates could find application as shrimp preservatives by inhibiting melanosis and by preventing the growth of bacteria during the storage.