Antiviral Properties of Prodelphinidin B-2 3′- O -Gallate from Green Tea Leaf

Prodelphinidin B-2 3′-O-gallate, a proanthocyanidin gallate isolated from green tea leaf, was investigated for its anti-herpes simplex virus type 2 properties in vitro. Prodelphinidin B-2 3′-O-gallate exhibited antiviral activity with IC₅₀ of 5.0 ± 1.0 μM and 1.6 ± 0.3 μM for XTT and plaque reduction (PRA) assays, respectively. Cytotoxicity assay had shown that prodelphinidin B-2 3′-O-gallate possessed cytotoxic effect toward Vero cell at concentration higher than its IC₅₀. The 50% cytotoxic concentration for cell growth (CC₅₀) was 33.3 ± 3.7 μM. Thus, the selectivity index (SI) (ratio of IC₅₀ to CC₅₀) for XTT assay and PRA was 6.7 and 20.8, respectively. Prodelphinidin B-2 3′-O-gallate significantly reduced viral infectivity at concentrations 10 μM or more. Result of time-of-addition studies suggested that prodelphinidin B-2 3′-O-gallate affected the late stage of HSV-2 infection. In addition, it was also shown to inhibit the virus from attaching and penetrating into the cell. Thus, prodelphinidin B-2 3′-O-gallate was concluded to possess antiviral activity with mechanism of inhibiting viral attachment and penetration, and disturbing the late stage of viral infection.