Screening of antioxidant and tyrosinase inhibition activities of spicy vegetables in Vietnam and application of Persicaria odorata leaf extract to preservative white leg shrimp (Litopenaus vannamei)

Abstract

In this study, we aimed to exploit natural extracts from the spicy vegetables, which are rich in phenolic compounds as an initial treatment step in the cold storage process for shrimp. Firstly, 40 extracts from 10 types of spicy vegetables in Vietnam were prepared and tested for their bioactivities. Among samples, the extract from Persicaria Odorata leaves (E-4) exhibited the highest potential of scavenging DPPH free radical (IC₅₀ of 7.54 µg.mL^-1) and decreasing tyrosinase activity with the inhibition percentage of 54.2 % at the concentration of 100 mg/mL. Twenty-two out of a total of 36 chemical compounds in the E-4 extract identified using HPLC-MS technique were phenolic compounds, in which four compounds (morin, quercetin, fisetin, astragalin) are flavonoids. Shrimp (Litopenaus vannamei) samples were treated with the E-4 extract having lower gray values, lipid peroxidation values, and microbiological counts than those of the control samples after 7 days of storage at 2 ^oC. These results show the potential of using the natural extract as a safe and effective alternative for commercial chemical-derived preservatives in the shrimp storage process.

Key words
Antioxidant activity; tyrosinase inhibition activity; Litopenaus vannamei; Persicaria odorata; spice vegetables