Antiviral activities of extracts from Hong Kong seaweeds

Abstract

We extracted six Hong Kong brown seaweed species with hot water for their antiviral properties. The cytotoxicity and antiviral activity of these extracts were tested by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenlytetrezolium bromide] method, cytopathic effect reduction assay, and plaque reduction assay. The antiviral effect was further determined by flow cytometric analysis. The results showed that most of these extracts inhibited the propagation of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) standard strains with very low cytotoxicity to the host cells. The extracts of Hydroclathrus clathratus and Lobophora variegata showed more potential anti-HSV activities than the extracts of the other four seaweeds. They also had moderate anti- respiratory syncytial virus (RSV) activities but could not inhibit influenza A virus. Hydroclathrus clathratus was further extracted by diluted acid and alkali and the antiviral effects of the extracts were also detected. The result showed that the hot water extract contained the main carbohydrate components that exhibited the antiviral activities against various strains of HSV, including the acyclovir-resistant strain. HI-3, a compound fractionated from this hot water extract, showed a dose-dependent anti-HSV activity in flow cytometric analysis and plaque reduction assay.

Figures

Fig. 1

CPE reduction assay showing the inhibitory effect of H. clathratus extract on HSV-1 Vero cells were infected with HSV-1 15577 strain and treated with the test sample at the final concentrations of (a) 0 μg/ml (acted as viral control), (b) 3.1 μg/ml, (c) 6.25 μg/ml, (d) 12.5 μg/ml, and (e) 25 μg/ml. The cell control is exhibited in (f). The arrows point out distinct CPE induced by the virus

Fig. 1

CPE reduction assay showing the inhibitory effect of H. clathratus extract on HSV-1 Vero cells were infected with HSV-1 15577 strain and treated with the test sample at the final concentrations of (a) 0 μg/ml (acted as viral control), (b) 3.1 μg/ml, (c) 6.25 μg/ml, (d) 12.5 μg/ml, and (e) 25 μg/ml. The cell control is exhibited in (f). The arrows point out distinct CPE induced by the virus

Fig. 1

CPE reduction assay showing the inhibitory effect of H. clathratus extract on HSV-1 Vero cells were infected with HSV-1 15577 strain and treated with the test sample at the final concentrations of (a) 0 μg/ml (acted as viral control), (b) 3.1 μg/ml, (c) 6.25 μg/ml, (d) 12.5 μg/ml, and (e) 25 μg/ml. The cell control is exhibited in (f). The arrows point out distinct CPE induced by the virus

Fig. 1

CPE reduction assay showing the inhibitory effect of H. clathratus extract on HSV-1 Vero cells were infected with HSV-1 15577 strain and treated with the test sample at the final concentrations of (a) 0 μg/ml (acted as viral control), (b) 3.1 μg/ml, (c) 6.25 μg/ml, (d) 12.5 μg/ml, and (e) 25 μg/ml. The cell control is exhibited in (f). The arrows point out distinct CPE induced by the virus

Fig. 1

CPE reduction assay showing the inhibitory effect of H. clathratus extract on HSV-1 Vero cells were infected with HSV-1 15577 strain and treated with the test sample at the final concentrations of (a) 0 μg/ml (acted as viral control), (b) 3.1 μg/ml, (c) 6.25 μg/ml, (d) 12.5 μg/ml, and (e) 25 μg/ml. The cell control is exhibited in (f). The arrows point out distinct CPE induced by the virus

Fig. 1

CPE reduction assay showing the inhibitory effect of H. clathratus extract on HSV-1 Vero cells were infected with HSV-1 15577 strain and treated with the test sample at the final concentrations of (a) 0 μg/ml (acted as viral control), (b) 3.1 μg/ml, (c) 6.25 μg/ml, (d) 12.5 μg/ml, and (e) 25 μg/ml. The cell control is exhibited in (f). The arrows point out distinct CPE induced by the virus

Fig. 2

Antiviral effect of HI-3 against standard strain of HSV-1 as analyzed by flow cytometric system These histograms depict FITC-fluorescence level from the anti-HSV-1 antibody in (a) cell control, (b) HSV-1 control, and HSV-1-infected Vero cells that had been treated with (c) 3.13 μg/ml of dextran sulfate (positive control), or (d) 1.56 μg/ml HI-3, (e) 3.13 μg/ml HI-3, (f) 6.25 μg/ml HI-3. In each histogram, B bar indicates the proportion of cells that were positive for the HSV-1 antigen

Fig. 2

Antiviral effect of HI-3 against standard strain of HSV-1 as analyzed by flow cytometric system These histograms depict FITC-fluorescence level from the anti-HSV-1 antibody in (a) cell control, (b) HSV-1 control, and HSV-1-infected Vero cells that had been treated with (c) 3.13 μg/ml of dextran sulfate (positive control), or (d) 1.56 μg/ml HI-3, (e) 3.13 μg/ml HI-3, (f) 6.25 μg/ml HI-3. In each histogram, B bar indicates the proportion of cells that were positive for the HSV-1 antigen

Fig. 2

Antiviral effect of HI-3 against standard strain of HSV-1 as analyzed by flow cytometric system These histograms depict FITC-fluorescence level from the anti-HSV-1 antibody in (a) cell control, (b) HSV-1 control, and HSV-1-infected Vero cells that had been treated with (c) 3.13 μg/ml of dextran sulfate (positive control), or (d) 1.56 μg/ml HI-3, (e) 3.13 μg/ml HI-3, (f) 6.25 μg/ml HI-3. In each histogram, B bar indicates the proportion of cells that were positive for the HSV-1 antigen

Fig. 2

Antiviral effect of HI-3 against standard strain of HSV-1 as analyzed by flow cytometric system These histograms depict FITC-fluorescence level from the anti-HSV-1 antibody in (a) cell control, (b) HSV-1 control, and HSV-1-infected Vero cells that had been treated with (c) 3.13 μg/ml of dextran sulfate (positive control), or (d) 1.56 μg/ml HI-3, (e) 3.13 μg/ml HI-3, (f) 6.25 μg/ml HI-3. In each histogram, B bar indicates the proportion of cells that were positive for the HSV-1 antigen

Fig. 2

Antiviral effect of HI-3 against standard strain of HSV-1 as analyzed by flow cytometric system These histograms depict FITC-fluorescence level from the anti-HSV-1 antibody in (a) cell control, (b) HSV-1 control, and HSV-1-infected Vero cells that had been treated with (c) 3.13 μg/ml of dextran sulfate (positive control), or (d) 1.56 μg/ml HI-3, (e) 3.13 μg/ml HI-3, (f) 6.25 μg/ml HI-3. In each histogram, B bar indicates the proportion of cells that were positive for the HSV-1 antigen

Fig. 2

Antiviral effect of HI-3 against standard strain of HSV-1 as analyzed by flow cytometric system These histograms depict FITC-fluorescence level from the anti-HSV-1 antibody in (a) cell control, (b) HSV-1 control, and HSV-1-infected Vero cells that had been treated with (c) 3.13 μg/ml of dextran sulfate (positive control), or (d) 1.56 μg/ml HI-3, (e) 3.13 μg/ml HI-3, (f) 6.25 μg/ml HI-3. In each histogram, B bar indicates the proportion of cells that were positive for the HSV-1 antigen