Antiviral activity of monoterpenes beta-pinene and limonene against herpes simplex virus in vitro

Abstract

Background and objectives: Essential oils are complex mixtures containing compounds of several different functional- group classes. Depending on the structure, we can distinguish monoterpenes, phenylpropanes, and other components. Here in this study two monoterpene compounds of essential oils, i.e. β-pinene and limonene were examined for their antiviral activity against herpes simplex virus type 1 (HSV-1) in vitro.

Material and methods: All antiviral assays were performed using RC-37 cells. Cytotoxicity was determined in a neutral red assay, antiviral assays were performed with HSV-1 strain KOS. The mode of antiviral action was evaluated at different periods during the viral replication cycle. Acyclovir was used as positive antiviral control.

Results: Beta-pinenene and limonenen reduced viral infectivity by 100 %. The mode of antiviral action has been determined, only moderate antiviral effects were revealed by monoterpenes when these drugs were added to host cells prior infection or after entry of HSV into cells. However, both monoterpenes exhibited high anti-HSV-1 activity by direct interaction with free virus particles. Both tested drugs interacted with HSV-1 in a dose-dependent manner thereby inactivating viral infection.

Conclusions: These results suggest that monoterpenes in essential oils exhibit antiherpetic activity in the early phase of viral multiplication and might be used as potential antiviral agents.

Keywords: antiviral activity; herpes simplex virus; mode of action; monoterpenes.

Fig 1

Structural formulas of monoterpenic compounds.

Fig 2

Pretreatment of cells. Antiviral activity of selected monoterpenes against herpes simplex virus type 1 after pretreatment of cells with drugs. Prior to viral infection, cells were incubated with maximum noncytotoxic concentrations of drugs for 1h at 37°C. Number of virus plaques was determined 3 d after infection and compared to untreated control. Results are expressed as percentage of plaque reduction. These experiments were repeated independently and data presented are the mean of three experiments.

Fig 3

Pretreatment of virus. Antiviral activity of selected monoterpenes against herpes simplex virus type 1 after incubation of HSV with drugs. HSV was incubated for 1 h at roomtemperature with maximum noncytotoxic concentrations of drugs. Number of virus plaques was determined 3 d after infection and compared to untreated control. Results are expressed as percentage of plaque reduction. These experiments were repeated independently and data presented are the mean of three experiments.

Fig 4

Replication. Antiviral activity of selected monoterpenes against herpes simplex virus type 1 during intracellular virus replication. Drugs were applied to HSV-1 infected cells after penetration of the viruses into cells for 3 d. Number of virus plaques was determined 3 d after infection and compared to untreated control. Results are expressed as percentage of plaque reduction. These experiments were repeated independently and data presented are the mean of three experiments.