Anti-herpes simplex virus effect of algal polysaccharide extract from Ulva reticulata

Herpes simplex virus (HSV) is the causative agent of a fever blister, genital herpes and neonatal herpes. Treatment of HSV infection was performed by acyclovir. Acyclovir remains to have a side effect in the case of long-term usage, and the virus may develop drug resistance. Therefore, these problems are interesting to study the natural substance for the treatment of HSV infection and drug-resistant HSV infection. In the present, edible algae are supplied as a healthy food because algae contain high nutrition and have many active compounds that are beneficial to health. Therefore, the algal extract can be used as an alternative agent for the treatment of HSV infection. The purpose of this research was to investigate the inhibitory effect of the algal polysaccharide extracts from Ulva reticulata against herpes simplex virus type 1 and type 2 infection in Vero cell. The structure of polysaccharide was analyzed by FT-IR technique. The algal polysaccharide extract from U. reticulata represents S=O and C–O–S of sulfate group. Besides, the toxicity of algal polysaccharide extract on Vero cell was evaluated by MTT assay. The algal polysaccharide extract from U. reticulata showed low toxicity on the cells with 50% cytotoxic concentration was greater than 5000 μg/mL. Inhibition of HSV infection was determined on Vero cell using plaque reduction assay. The results indicated that the algal polysaccharide extracts from U. reticulata showed antiviral activity against HSV-1 upon treatment before, meanwhile and after viral adsorption with 50% effective concentration of 2,525.90, 58.32 and 263.95 μg/mL, respectively. Also, the algal polysaccharide extracts from U. reticulata showed antiviral activity against HSV-2 upon treatment before, meanwhile and after viral adsorption with EC50 of 163.26, 9.70 and 527.28 μg/mL, respectively. Besides, HSV-1 and HSV-2 viral particles were inactivated by the polysaccharide extract from U. reticulata. In summary, the polysaccharide extract from U. reticulata could protect Vero cell from HSV infection, inhibit HSV infection and inactivate HSV particles. Therefore, it will be useful to apply U. reticulata polysaccharide extract as a potential anti-HSV agent.