Full Length Research Paper
Abstract
Efficacy of Rhinacanthus nasutus and Stemona tuberosa against herpes simplex viruses (HSV) was evaluated in this study. The cytotoxicities of the medicinal plant extracts were tested on Vero cell. 50% cytotoxic doses (CD50) of aqueous extracts of R. nasutus and S. tuberosa were 1268.0 and 5677.0 μg/ml, whereas ethanolic extracts of R. nasutus and S. tuberosa showed CD50 of 50.4 and 1426 μg/ml, respectively. Both types of HSV were treated with the highest non-toxic concentrations of aqueous and ethanolic extracts. Inhibitory effect of these plant extracts on HSV infection was investigated by plaque reduction assay. It was found that ethanolic extract of S. tuberosa showed anti-HSV-1 when treated before viral attachment with therapeutic index (TI) value of 41.30 ± 0.25 followed by ethanolic extract of R. nasutus with TI value of 15.76 ± 2.04, and aqueous extract of S. tuberosa showed anti-HSV-2 with TI value of 3.64 ± 0.01. During viral attachment, ethanolic extract of S. tuberosa showed anti-HSV-1 with TI value of 10.75 ± 0.13, whereas aqueous extract of R. nasutus inhibited HSV-2 with TI value of 4.16 ± 0.02. Furthermore, ethanolic extracts of R. nasutus and S. tuberosa inhibited HSV-1 after viral attachment with high TI value of 37.78 ± 1.4 and 5.79 ± 0.14, whereas aqueous extract of S. tuberosa showed high TI values of 5.79 ± 0.02 and 7.23 ± 0.03 on HSV-1 and HSV-2, respectively. Moreover, viral particles were inactivated directly. Aqueous extracts of R. nasutus and S. tuberosa inhibited HSV-1 particles by 92.23 ± 0.98 and 89.12 ± 2.14%, respectively at 4 h of treatment. Ethanolic extracts of R. nasutus and S. tuberosa inhibited HSV-2 particles by 95.12 ± 1.43 and 94.11 ± 1.43%, respectively at 4 h of treatment. In addition, the highest reduction of log titer of HSV-1 and HSV-2 was observed at 30 h after treatment with ethanolic extract of R. nasutus by 3.07 ± 0.28 and 3.52 ± 0.34, respectively. Therefore, extracts of R. nasutus andS. tuberosa showed promising anti-HSV activity.
Key words: Herpes simplex virus, antiviral activity, medicinal plant, Rhinacanthus nasutusL., Stemona tuberosa L.
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