The Inhibitory Effects of Eucalyptus Extract on Herpes Simplex Virus-1 Replication in Baby Hamster Kidney Cells

In recent years, following the increasing of drug resistant strain of viruses, there has been an increasing interest in the use of natural substances with antiviral activity and low side effects. One of these herbal medicines, Eucaliptus, has shown some therapeutic effects including antibacterial and antiviral activities. Therefore, this study aimed to determine the minimum inhibitory concentration of hydroalchoholic extract of Eucaliptus on Herpes simplex virus-1 (HSV-1) in vitro. In this experimental study, the hydroalchoholic extract of Eucalyptus leaves was prepared using 70% ethanol through maceration method. Baby Hamster Kidney (BHK) cells were grown in monolayer culture with Dulbecco's modified Eagle's medium (DMEM) supplemented with 5% fetal calf serum and plated onto 48-well culture plates. 50% cytotoxic concentration (CC50%) of the extract on BHK cells was determined, and subsequently 50% inhibitory concentration (IC50%) of the herbal extract on replication of HSV-1 both in extracellular and intracellular cases was assessed. Based on Probit analysis, CC50% of the extract was 0.650mg/ml. Significant relationships between the concentration of the extract and cell death in the cell studied were shown using the Probit model (p<0.01). IC50s of the extract on the virus before cellular attachment and after entering the cells were 456.82ug/ml and 180.75ug/ml, respectively. Based on the model, with increasing the extract concentration, the percentage of inhibition of cytopathic effect (CPE) in both stages was increased (p<0.05). Based on the findings of this study, hydroalchoholic extract of Eucaliptus could be probably an appropriate anti herpetic herbal medicine.