Phytochemical and Molecular Insights Into the Antiviral Efficacy of Juglans regia (Walnut) Leaf Ethanolic Extract and Cydonia oblonga (Quince) Fruit Acetone Extract in Litopenaeus vannamei Infected With White Spot Syndrome Virus (WSSV).

White Spot Syndrome Virus (WSSV) is known to cause significant mortality in farmed shrimp, including black tiger shrimp (Penaeus monodon) and white leg shrimp (Litopenaeus vannamei) across several countries. Prolonged infections with WSSV are difficult to eliminate with traditional methods like vaccinations, probiotics, and immunostimulants. Herein, we assessed the antiviral effectiveness of two medicinal plants, Cydonia oblonga and Juglans regia, against WSSV. The crude ethanolic leaf extract of J. regia and the acetone fruit extract of C. oblonga were evaluated through phytochemical analysis, GC-MS profiling, in silico studies, in vivo toxicity assessment, and antiviral validation. The presence of bioactive substances, such as phenolics, flavonoids, and antioxidants known for their strong antiviral and immunomodulatory properties, was verified by phytochemical analysis. In particular, the important bioactive constituents with known antiviral potential, including naringenin, juglone, kaempferol, beta-sitosterol, quercetin, and epicatechin, were confirmed in these plant extracts by GC-MS analysis. Strong binding affinities of these medicines to the VP28 envelope protein of WSSV were shown in silico molecular docking studies, with the binding energies ranging from -6.0 to -8.9 kcal/mol. Significant protection against WSSV challenge was demonstrated by in vivo neutralisation tests. Pairwise comparisons confirmed extremely significant differences between the treated and untreated infected groups, and these results were statistically significant (p ≤ 0.05). Molecular diagnostics by PCR provided additional confirmation of the antiviral activity of the medicinal plants, coupled with a Western blot assay and an indirect ELISA. Taken together, the findings suggest that the studied medicinal plants can offer a safe, affordable, and environmentally beneficial substitute for synthetic antiviral drugs in aquaculture.