Abstract
Herpes simplex virus (HSV) is a causative agent of fever blister, genital herpes, and neonatal herpes. Nowadays, edible algae are recognized as health food due to high nutrition content and their many active compounds that are beneficial to health. The purpose of this study is to investigate the inhibitory effects of algal polysaccharide extract from Cladophora spp. against herpes simplex virus type 1 and type 2 on Vero cells. In this study, the structure of polysaccharide extract is presented as S=O and C-O-S of the sulfate group, as identified by the FT-IR technique. The toxicity of algal polysaccharide extract on Vero cells was determined by MTT assay. The algal extract showed low toxicity on the cells, with 50% cytotoxic concentration (CC50) value greater than 5000 µg mL-1. The inhibition of HSV infection by the algal extract was then evaluated on Vero cells using plaque reduction assay. The 50% effective concentration (EC50) values of algal extract exhibited antiviral activity against HSV-1 upon treatment before, during, and after viral adsorption with and without removal of the extract were 70.31, 15.17, > 5000 and 9.78 µg mL-1, respectively. Additionally, the EC50 values of algal extract against HSV-2 upon treatment before, during and after viral adsorption with, and without removal of the extract were 5.85, 2.57, > 5000 and 26.96 µg mL-1, respectively. Moreover, the algal extract demonstrated direct inactivation of HSV-1 and HSV-2 virions as well as inhibitory effect against HSV replication. Accordingly, algal polysaccharide extract containing sulfated polysaccharides showed strong activity against HSV. Therefore, it is proved to be useful to apply Cladophora spp. polysaccharide extract as an anti-HSV agent.