Antiviral activity of 9(10H)-Acridanone extracted from marine Streptomyces fradiae strain VITMK2 in Litopenaeus vannamei infected with white spot syndrome virus

The aim of the present study was to screen the antiviral activity of the secondary metabolite 9(10H)-Acridanone extracted from Streptomyces fradiae strain VITMK2 in Litopenaeus vannamei shrimp infected with white spot syndrome virus (WSSV). The strain was isolated from marine soil sediment sample collected from the mangrove forest region of Pichavaram, Tamil Nadu, India. Among the 31 isolates, the isolate VITMK-2 exhibited strong antiviral activity against the WSSV. The potential isolate was subjected to morphological, biochemical and molecular taxonomic characterisation. It was identified as Streptomyces species and designated as S. fradiae strain VITMK2. Purification of ethyl acetate (EA) extract by silica gel column chromatography yielded two compounds, C1 and C2. The shrimp infected with WSSV and treated with C1 compound (500 μg, 250 μg, and 125 μg) showed survival rates of 88.89%, 83.33% and 55.56% respectively. The survival of shrimp treated with the EA extract of S. fradiae strain VITMK2 (500 μg/animal) was 83.33%. The C1 compound (250 μg/animal) showed better antiviral activity when compared to EA extract. The chemical nature of the C1 compound was identified by FTIR, 1H and 13C NMR, and HRMS analysis. Based on the spectral data, the C1 compound was identified as 9(10H)-Acridanone with a molecular formula of C13H9NO and a molecular mass of 195.1048 Da. Docking of the lead compound with VP26 and VP28 of WSSV drug target proteins showed the least binding energy of −5.71 kcal/mol and −5.21 kcal/mol respectively predicting the strong interaction of the compound with VP26 and VP28. This is the first report on anti-WSSV activity of 9(10H)-Acridanone derived from marine S. fradiae strain VITMK2 and this compound can be probed further to be used as an effective antiviral agent for better control and management of WSSV infection in aquaculture farms.