Anti-herpes virus activity of Dunbaria bella Prain.

The herpes inhibitory effect of Dunbaria bella Prain (Fabaceae), a Thai medicinal plant traditionally used to treat viral infections was investigated. Using a bioassay-guided fractionation procedure, tertiary fractionation of a dichloromethane-methanol plant extract afforded a partially purified fraction (Fr.372) equally active against replication of herpes simplex virus (HSV) types 1 and 2. The 50% inhibitory concentration determined by a viral yield-inhibition assay was 1.21-1.25 microg/ml and the antiviral selectivity was about 17-fold. Treatment of HSV with high concentrations of Fr.372 followed by removal before infection had little effect on subsequent viral yield indicating the active principle(s) were not inactivating the virus. Concentrations greater than 0.5 microg/ml significantly inhibited viral release more than cell-associated virus suggesting that one or more active ingredients may inhibit viral release. Furthermore, the antiviral activity was dependent on multiplicity of infection and the type of host cell. Preliminary chemical analysis showed that Fr.372 contained neither phenolic compounds nor alkaloids.