Tanacetum vulgare: anti-herpes virus activity of crude extract and the purified compound parthenolide

Abstract

Herpes simplex virus type 1 is a common human pathogen which causes several infectious diseases. In immunocompetent hosts these clinical symptoms are usually benign, but in immunocompromised patients they become severe [1]. Nucleoside analogues, such as acyclovir, have been successfully used to treat herpetic infections. However, resistant strains and drug toxic side effects encourage the search for new compounds to improve the current antiviral arsenal [2]. The present study demonstrated that the ethyl-acetate extract and the compound parthenolide, isolated from aerial parts of Tanacetum vulgare L. (Asteraceae), were able to protect Vero cells from herpes simplex virus (HSV-1) infection in vitro. The extract and parthenolide were assayed against HSV-1 by sulforhodamine B colorimetric assay, and exhibited anti-HSV-1 activity with an EC50 of 40µg/ml and 0.3µg/ml, respectively. In order to determine which step of the virus-cell interaction was affected by parthenolide, the pure compound from a commercial source was used. No effect was observed when both viruses and cells were pre-treated, suggesting that parthenolide neither inactivated virus particles directly nor protected the cell from infection, but interfered with the virus replication after the penetration step, inhibiting approximately 80% of plaques formed at a concentration of 2.5µg/ml when compared with an untreated control. These results demonstrate that parthenolide is one of the compounds responsible for the antiviral activity of T. vulgare, contributing to its validation as a medicinal plant useful in the treatment of diseases caused by HSV-1.