Antiviral potential of aqueous extract of star anise Illicium verum against fish nodavirus

We tested the antiviral activity of aqueous extract of star anise Illicium verum (AEIV) against striped jack nervous necrosis virus (SJNNV) in vitro as well as in vivo using the Sahul Indian Seabass Spleen (SISS) cell line and Asian seabass Lates calcarifer. Preliminary results from GC-MS profiling and polyphenol content estimation of AEIV revealed the antiviral potential of the extract. Before testing the compound, the extract was assessed for its toxic potential in an in vitro model (SISS cell line) using 4 different concentrations (50, 75, 100 and 200 µg ml-1) of AEIV through MTT and neutral red assays. The tested concentrations were not toxic (≥90% survival). Subsequently, the same concentrations of AEIV were tested for their antiviral potential against SJNNV in SISS cells. The results showed that AEIV at higher concentration (100 and 200 µg ml-1) effectively inhibited SJNNV replication in the SISS cells. RT-PCR and qPCR confirmed the inhibition of the virus. The same concentrations were then used to evaluate their antiviral efficacy in vivo by intraperitoneal injection in Asian seabass. We observed 100% mortality only in the fish injected with SJNNV (control), which confirms that AEIV possesses the potency to control the replication of SJNNV under both in vitro and in vivo conditions. The present study indicates that medication with plant extracts having antiviral activity could be a potentially beneficial alternative to the usage of chemotherapeutics in aquaculture.