Acetone, ethanol and methanol extracts of Phyllanthus urinaria inhibit HSV-2 infection in vitro

Phyllanthus urinaria Linnea (Euphorbiaceae) is one of the traditional medicinal plants that are widely applied by oriental people, especially by Chinese and Indian, to ameliorate various kinds of ailments. Many biological activities, including anti-hepatitis B virus, anti-Epstein-Barr virus and anti-retroviral reverse transcriptase, of P. urinaria have been reported, but not against herpes simplex virus (HSV). In this study, the anti-HSV-1 and HSV-2 activities of different solvents extracted from P. urinaria were investigated in vitro by plaque reduction assay. Results showed that acetone, ethanol and methanol extracts of P. urinaria inhibited HSV-2 but not HSV-1 infection. The 50% inhibitory concentration against HSV-2 infection (IC50) of acetone, ethanol and methanol extracts was 4.3 ± 0.5, 5.0 ± 0.4 and 4.0 ± 0.9 mcg/ml, respectively. All three extracts showed no cytotoxic effect against Vero cells at concentrations of 10.0 mcg/ml or below. The time-of-addition study demonstrated that these three extracts were only effective when added during the HSV-2 infection which, therefore, suggested that they disturb the initial stage of HSV-2 infection. Furthermore, they can diminish virus infectivity without significantly affecting incubation time and temperature. Therefore, the acetone, ethanol and methanol extracts of P. urinaria were concluded to likely inhibit HSV-2 infection through disturbing the early stage of virus infection and through diminishing the virus infectivity.