Comparative study on the antiherpetic activity of aqueous and ethanolic extracts derived from Cajanus cajan (L.) Millsp.

BACKGROUND

Aqueous and ethanolic extracts of Cajanus cajan (Fabaceae) were examined in vitro for their antiviral activity against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2).

METHODS

The antiviral activity was determined using a plaque reduction assay. The cytotoxic concentration (CC50) as well as the inhibitory concentration (IC50) of the extracts was determined from dose-response curves.

RESULTS

All extracts tested revealed a high antiviral activity against cell-free HSV-1 and HSV-2. The most active one was the Cajanus ethanol extract with IC50 values of 0.022 microg/ml for HSV-1 and 0.1 microg/ml for HSV-2. In order to identify the mode of antiviral action, the extracts were added to the host cells or viruses at different stages of infection. HSV-1 and HSV-2 were considerably inactivated when the viruses were pretreated with the extracts for 1 h prior to cell infection. At maximum non-cytotoxic concentrations of the extracts, plaque formation was significantly reduced by 95-99% for HSV-1 and HSV-2. In a time-dependent assay with cell-free HSV-1 over a period of 2 h, a clearly time-dependent effect was demonstrated whereby the Cajanus ethanol extract revealed a much higher activity than the Cajanus aqueous one.

CONCLUSIONS

The results obtained indicate that the extracts affect HSV before cell adsorption, but have no effect on the intracellular virus replication. According to our findings, a therapeutic application of Cajanus ethanolic extracts containing crème or ointment as antiviral agent in recurrent HSV infection appears to be promising.