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Grouper iridovirus causes high mortality rates in cultured groupers, and effective treatment for grouper iridovirus infection is urgently required. Illicium verum Hook. f. is a well‐known medicinal plant with a variety of biological activities. The aim of this study was to analyse the use of I. verum extracts to treat grouper iridovirus infection. The safe working concentration of each I. verum extract was identified both in vitro and in vivo as follows: I. verum aqueous extract (IVAE) ≤ 500 μg/ml; I. verum ethanol extract (IVEE) ≤ 250 μg/ml; shikimic acid (SKA) ≤ 250 μg/ml; trans‐anethole (TAT) ≤ 800 μg/ml; 3,4‐dihydroxybenzoic acid (DDBA) ≤ 400 μg/ml; and quercetin (QCE) ≤ 50 μg/ml. The inhibitory activity of each I. verum extract against grouper iridovirus infection was analysed using aptamer (Q2)‐based fluorescent molecular probe (Q2‐AFMP) and RT‐qPCR. All of the I. verum extracts displayed dose‐dependent antiviral activities against grouper iridovirus. Based on the achieved per cent inhibition, IVAE, IVEE, DDBA and QCE were associated with the greatest antiviral activity (all > 90%). Together, our results indicate that I. verum extracts have effective antiviral properties, making it an excellent potential source material for the development of effective treatment for grouper iridovirus infection. [ABSTRACT FROM AUTHOR]

Grouper iridovirus was isolated from the diseased hybrid grouper in Guangxi province, China (SGIV-Gx), which has a high mortality rate in cultured groupers. Effective medicines for controlling SGIV-Gx infection are urgently needed. Lonicera japonica Thunb. (L. japonica) is a well-known medicinal plant. The application of L. japonica components against SGIV-Gx infection was assessed in this study. The safe, appropriate working concentration of each L. japonica component was identified (L. japonica aqueous extracts LAE ≤ 10 mg/mL; chlorogenic acid, CGA ≤ 250 μg/mL; cryptochlorogenic acid, CCGA≤500 μg/mL; isochlorogenic acid A, IAA ≤ 250 μg/mL; isochlorogenic acid B, IAB ≤ 250 μg/mL; isochlorogenic acid C, IAC ≤ 500 μg/mL; caffeic acid, CA ≤ 125 μg/mL; luteolin (LT) and inositol (IS), no cytotoxic effects even at 2000 μg/mL) in vitro and in vivo. The inhibitory activities of each L. japonica component against SGIV-Gx infection were analyzed by three methods: light microscopy, Q3-AFMP and RT-qPCR, which proved that, some L. japonica components (LAE, IAA, IAB, IAC, CA, LT, IS) exhibited the antiviral activity against SGIV-Gx infection in a dose-dependent manner, and LAE, IAA, IAB, IAC, CA, LT had the best antiviral activity against SGIV-Gx infection, with above 90% of inhibitory percentage. Overall, the results in this study suggest that L. japonica components have antiviral effects, making this plant a promising candidate for developing effective medicines for preventing and controlling SGIV-Gx infection in farmed groupers. • L. japonica components displayed antiviral activities against grouper iridovirus infection. • L. japonica ingredients LAE, IAA, IAB, IAC, CA, LT had the best antiviral activity. • L. japonica is a promising candidate for developing effective medicines for controlling SGIV-Gx infection. [ABSTRACT FROM AUTHOR]