Abstract
Rapid production of prawn (Litopenaeus vannamei) under artificial pressure can result in a series of obvious challenges and is vulnerable to serious losses related to aquatic environmental issues and the unrestrained outbreak of white spot syndrome (WSS). However, to date, there are no therapeutic strategies to contain the spread of the virus. Here, we synthesized 27 coumarin derivatives and evaluated their anti-white spot syndrome virus (WSSV) activity in L. vannamei larvae. We demonstrated that electron-withdrawing and electron-giving substituent groups play an important role in reducing toxicity and WSSV replication, respectively. Two coumarin C2 (2-amino-5-oxo-4-(p-tolyl)-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile) and C7 (2-amino-4-(4-chlorophenyl)-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile) were regarded as the most promising anti-WSSV compounds with maximum antiviral response <5% and median effective concentration <10 mg/L. The mortality of WSSV-infected larvae decreased by more than 60% after exposure to C2 and C7. With continuous immersion of C2 and C7 exchange, the mortality further decreased to 40% at 120 h. Additionally, C2 and C7 are the relatively stable in aquacultural water, making these agents suitable for use in inhibiting WSSV horizontal transmission in static aquaculture systems. These results showed the marked advantages of using C2 and C7 in the shrimp industry, and suggest that they hold potential for the treatment and prevention of WSSV infection in shrimp seedling culture.
Highlights
white spot syndrome virus (WSSV) caused a significant loss in the shrimp sector, in the culture of shrimp seedlings [25]
Based on preliminary analysis of the structure-activity relationship (SAR) of similar spatial structures with different substituents of electron-donating and electron-withdrawing groups to coumarins A1, B1, and C1, we considered that electron-withdrawing groups could reduce the toxicity of compounds; this provides a basis for further research
To address the negative effects of C2 and C7 during the WSSV infection cycle, the virus was pre-incubated with the compounds for 1–4 h prior to infection of larvae (Figure 4).The results showed a suppressed WSSV infection (Figure 4B) and increased the survival rate by up to 40% (Figure 4C,D)
Summary
Among the main species of aquaculture, seawater and low-salinity brackish-water shrimp culture farming has become a global industry as one of the most economically productive activities, given that the total global production of shrimp is more than 4.7 million tons in 2019, based on the report of Global Aquaculture
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