Antiviral Activity of Liquorice Powder Extract against Varicella Zoster Virus Isolated from Egyptian Patients

Background: Varicella-zoster virus (VZV) is the etiologic agent of two diseases, varicella (chicken pox) and zoster (shingles). Varicella is a self- limited infection, while zoster is mainly a disease of adults. The present study was conducted to isolate VZV from clinically diagnosed children using cell cultures and compare the activity of liquorice powder extract, an alternative herbal antiviral agent, with acyclovir and interferon alpha 2a (IFN-α2a) against the isolated virus.Methods: Forty-eight VZV specimens, 26 from vesicular aspirates and 22 from vesicular swabs, from children clinically diagnosed with varicella were isolated on the Vero cell line. Isolates were propagated and identified with specific antiserum using indirect immunofluorescence and immunodot blotting assays.The growth kinetics of the viral isolates was studied. The antiviral activity of liquorice powder extract, acyclovir (ACV) and IFN-α2a was evaluated against the isolated virus.Results: VZV was successfully isolated in 4 of the 48 specimens, all from vesicular aspirates. The growth kinetics of the viral isolates was time dependent. The inhibitory activity of liquorice powder extract (containing 125 μg/ml glycyrrhizin) when compared to ACV (250 μg/ml) and IFN-α2a is the lowest.Conclusions: VZV isolates were successfully isolated and propagated using Vero cells. Isolates were identified using indirect immunofluorescent and immunodot blotting techniques. Growth kinetics of the isolates revealed an increase in the viral infectivity titer relative to time. Glycyrrhizin in the crude form has low antiviral activity against VZV compared with acyclovir and interferon.