Antiviral Activity of Ecklonia cava Extracts and Dieckol Against Zika Virus

Abstract

Ecklonia cava and its major compound dieckol, both natural marine products, possess antioxidant, anti-inflammatory, and metabolic-regulating effects. Zika virus (ZIKV), an arbovirus from the Flaviviridae family, is transmitted by mosquitoes and causes serious illnesses in humans. This study aimed to evaluate the anti-ZIKV potential of Ecklonia cava and dieckol. The antiviral activity of Ecklonia cava extract (ECE), prepared with 80% ethanol, was assessed in ZIKV-infected Vero E6 cells through MTT assay, plaque assay, and quantitative polymerase chain reaction (qPCR), demonstrating no cytotoxicity and a significant reduction in viral titers and ZIKV mRNA levels. In addition, ECE decreased the expression of tumor necrosis factor-α and interferon-induced protein with tetratricopeptide repeats in the ZIKV-infected cells. Dieckol, the primary active compound in ECE, exhibited potent anti-ZIKV activity, with a half maximal inhibitory concentration (IC₅₀), value of 4.8 µM. In silico molecular docking analysis revealed that dieckol forms stable complexes with key ZIKV proteins, including the envelope, NS2B/NS3, and RNA-dependent RNA polymerase (RdRp) protein, exhibiting high binding energies of -438.09 kcal/mol, -1040.51 kcal/mol, and -1043.40 kcal/mol, respectively. Overall, our findings suggest that ECE and dieckol are promising candidates for the development of anti-ZIKV agents.

Keywords: Ecklonia cava; Vero E6 cells; Zika virus; dieckol; in silico assays.

Figure 1

Anti-Zika virus activity of Ecklonia cava ethanol extract in virus-infected Vero E6 cells: (a) the cytotoxicity of ECE in Vero E6 cells using MTT assay; (b) plaque image; (c) virus was measured using plaque assay; (d) cell lysates were extracted, and the mRNA level of Zika virus NS1 was analyzed using qPCR. Values are expressed as mean ± SD of triplicate experiments. Different letters (a, b, c, d) indicate statistical significance (p < 0.05) and *** p < 0.001 indicate significant differences from PC. ECE: Ecklonia cava ethanol extract, qPCR: quantitative polymerase chain reaction, SD: standard deviation, MTT: (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium Bromide), PC: virus groups.

Figure 2

Effects of Ecklonia cava ethanol extracts on TNF-α and IFIT 1 and IFIT2 mRNA levels in Zika virus-infected Vero E6 cells. Cell lysates were extracted, and the mRNA levels of (a) TNF-α, (b), and (c) IFIT2 were analyzed using qPCR. Values are expressed as mean ± SD of triplicate experiments. ns: not significant, * p < 0.05, ** p < 0.005, *** p < 0.001 indicate significant differences from PC. TNF-α: tumor necrosis factor-α, IFIT: interferon-induced protein with tetratricopeptide repeats, qPCR: quantitative polymerase chain reaction, SD: standard deviation.

Figure 3

Anti-Zika virus activity of dieckol in virus-infected Vero E6 cells: (a) plaque image and titer were measured using plaque assay at 25 and 50 µM; (b) cytotoxicity and anti-Zika virus profiles (half-maximal inhibitory concentration; IC₅₀) of dieckol in Vero E6 cells at various concentrations 0.20–100 µM using MTT and plaque assay, respectively. Values are expressed as mean ± SD of triplicate experiments. **** p < 0.0001 indicates significant differences from PC. MTT: MTT: (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), SD: standard deviation, PC: virus groups.

Figure 4

The virucidal effect of dieckol: Cell lysates were extracted, and the mRNA levels of (a) ZIKV NS1, (b) TNF-α, (c), IFIT1, and (d) IFIT2 were analyzed using qPCR. Values are expressed as mean ± SD of triplicate experiments. ns: not significant, * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001 indicate significant differences from PC. PC: virus groups, TNF-α: tumor necrosis factor-α, IFIT: interferon-induced protein with tetratricopeptide repeats, qPCR: quantitative polymerase chain reaction, SD: standard deviation.

Figure 5

In silico docking assay for the docking poses of dieckol to the three main Zika virus proteins: (a) the envelope protein, (b) NS2B/NS3, and (c) RdRp.