Essential Oils and the Herpes Virus Scientific Studies
Antiviral activity of the volatile oils of Melissa (melissa essential oil) officinalis L. against Herpes simplex virus type-2.
Tropical Diseases Center, Faculty of Medicine, Cukurova University, Adana, Turkey.
Melissa officinalis L. (Lamiaceae) has been used in a variety of practical applications in medical science. Our objective in the current study was to determine the effects of the volatile oil components of M. officinalis on Herpes simplex virus type 2 (HSV-2) replication in HEp-2 cells. Four different concentrations (25, 50, 100, 150 and 200 microg/ml) of volatile oils were examined. Experiments were carried out using HEp-2 cells. M. officinalis volatile oil was found to be non-toxic to HEp-2 cells up to a concentration of 100 micro/ml. It was, however, found to be slightly toxic at a concentration over of 100 microg/ml. The antiviral activity of non-toxic concentrations against HSV-2 was tested. The replication of HSV-2 was inhibited, indicating that the M. officinalis L. extract contains an anti-HSV-2 substance.
Antiviral activity of Australian tea tree oil and eucalyptus oil against herpes simplex virus in cell culture.
Department of Virology, Hygiene Institute, University of Heidelberg, Germany.
The antiviral effect of Australian tea tree oil (TTO) and eucalyptus oil (EUO) against herpes simplex virus was examined. Cytotoxicity of TTO and EUO was evaluated in a standard neutral red dye uptake assay. Toxicity of TTO and EUO was moderate for RC-37 cells and approached 50% (TC50) at concentrations of 0.006% and 0.03%, respectively. Antiviral activity of TTO and EUO against herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) was tested in vitro on RC-37 cells using a plaque reduction assay. The 50% inhibitory concentration (IC50) of TTO for herpes simplex virus plaque formation was 0.0009% and 0.0008% and the IC50 of EUO was determined at 0.009% and 0.008% for HSV-1 and HSV-2, respectively. Australian tea tree oil exhibited high levels of virucidal activity against HSV-1 and HSV-2 in viral suspension tests. At noncytotoxic concentrations of TTO plaque formation was reduced by 98.2% and 93.0% for HSV-1 and HSV-2, respectively. Noncytotoxic concentrations of EUO reduced virus titers by 57.9% for HSV-1 and 75.4% for HSV-2. Virus titers were reduced significantly with TTO, whereas EUO exhibited distinct but less antiviral activity. In order to determine the mode of antiviral action of both essential oils, either cells were pretreated before viral infection or viruses were incubated with TTO or EUO before infection, during adsorption or after penetration into the host cells. Plaque formation was clearly reduced, when herpes simplex virus was pretreated with the essential oils prior to adsorption. These results indicate that TTO and EUO affect the virus before or during adsorption, but not after penetration into the host cell. Thus TTO and EUO are capable to exert a direct antiviral effect on HSV. Although the active antiherpes components of Australian tea tree and eucalyptus oil are not yet known, their possible application as antiviral agents in recurrent herpes infection is promising.
Inhibitory effect of essential oils against herpes simplex virus type 2.
Essential oils from anise, hyssop, thyme, ginger, chamomile and sandalwood were screened for their inhibitory effect against herpes simplex virus type 2 (HSV-2) in vitro on RC-37 cells using a plaque reduction assay. Genital herpes is a chronic, persistent infection spreading efficiently and silently as sexually transmitted disease through the population. Antiviral agents currently applied for the treatment of herpesvirus infections include acyclovir and its derivatives. The inhibitory concentrations (IC(50)) were determined at 0.016%, 0.0075%, 0.007%, 0.004%, 0.003% and 0.0015% for anise oil, hyssop oil, thyme oil, ginger oil, camomile oil and sandalwood oil, respectively. A clearly dose-dependent virucidal activity against HSV-2 could be demonstrated for all essential oils tested. In order to determine the mode of the inhibitory effect, essential oils were added at different stages during the viral infection cycle. At maximum noncytotoxic concentrations of the essential oils, plaque formation was significantly reduced by more than 90% when HSV-2 was preincubated with hyssop oil, thyme oil or ginger oil. However, no inhibitory effect could be observed when the essential oils were added to the cells prior to infection with HSV-2 or after the adsorption period. These results indicate that essential oils affected HSV-2 mainly before adsorption probably by interacting with the viral envelope. Camomile oil exhibited a high selectivity index and seems to be a promising candidate for topical therapeutic application as virucidal agents for treatment of herpes genitalis.
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