A spiroketal-enol ether derivative from Tanacetum vulgare selectively inhibits HSV-1 and HSV-2 glycoprotein accumulation in Vero cells Ángel L. Álvarez a,⇑ , Solomon Habtemariam b , Ahmed E. Abdel Moneim a,1 , Santiago Melón c , Kevin P. Dalton a , Francisco Parra a a Instituto Universitario de Biotecnología de Asturias, Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, 33006 Oviedo, Asturias, Spain b Pharmacognosy Research Laboratories, Medway School of Science, University of Greenwich, Central Avenue, Chatham-Maritime, Kent ME4 4TB, UK c Servicio de Microbiología, Laboratorio de Virología, Hospital Universitario Central de Asturias, Oviedo, Spain article info Article history: Received 19 November 2014 Revised 2 April 2015 Accepted 7 April 2015 Available online 13 April 2015 Keywords: Antiviral HSV Tanacetum Tansy Rhizome Spiroketals abstract The inhibitory effects of Tanacetum vulgare rhizome extracts on HSV-1 and HSV-2 in vitro replication were assessed. Unlike extracts obtained from the aerial parts, adsorption inhibition and virucidal activities seemed not to be relevant for the observed antiviral action of tansy rhizome extracts. Instead, the most significant effects were the inhibition of virus penetration and a novel mechanism consisting of the specific arrest of viral gene expression and consequently the decrease of viral protein accumulation within infected cells. Through a bioactivity-guided fractionation protocol we isolated and identified the spiroketal-enol ether derivative (E)-2-(2,4-hexadiynyliden)-1,6-dioxaspiro[4.5]dec-3-ene as the active compound responsible for this inhibitory effect. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Herpes simplex virus type 1 (HSV-1) and 2 (HSV-2) are envel- oped viruses with a large, linear, double-stranded DNA genome. HSV-1 and HSV-2 are major human pathogens responsible for long-term latent infections, with periods of recurring viral replica- tion. The clinical symptoms associated to herpesvirus recurrences may vary from mild self-limiting skin lesions in oral or genital areas to severe illnesses such as keratoconjunctivitis, encephalitis, pneumonia, hepatitis, Kaposi’s varicella-like eruption and ery- thema multiforme (Whitley et al., 1998; Roizman and Whitley, 2001; Whitley and Roizman, 2001). Furthermore, the incidence of genital HSV infections has not only risen in recent years but has also been linked with a 3-fold increased risk of acquiring HIV infec- tion (Freeman et al., 2006). The lack of an effective vaccine, the moderate to high toxicity of the available synthetic anti-herpes compounds (e.g., acyclovir, valaciclovir, penciclovir, famciclovir, vidarabine, cidofovir and foscarnet) and the appearance of resistant viral strains, especially among immunocompromised patients, emphasise the need for new inhibitors (James and Prichard, 2014; Piret and Boivin, 2014). The anti-herpesvirus activity of Tanacetum vulgare L. (tansy) aerial parts has previously been reported (Onozato et al., 2009). Further studies on the anti-herpetic constituents of the aerial parts revealed that the antioxidant compounds 3,5-dicaffeoylquinic acid and axillarin were the main antiviral molecules (Juan-Badaturuge et al., 2009; Álvarez et al., 2011). Since the crude rhizome extract also showed a remarkable anti-herpetic activity (Álvarez et al., 2011), the present study was designed to investigate the active chemical constituents along with their mechanisms of anti HSV-1 and HSV-2 action. 2. Material and methods 2.1. Plant material and extraction procedures T. vulgare from an authenticated source grown at Hadlow Agricultural College medicinal gardens (Hadlow, UK) was har- vested during March 2009 (Juan-Badaturuge et al., 2009). The underground rhizomes were air-dried and extracted with cold methanol as described previously (Álvarez et al., 2011). A portion of the crude extract (11 g) was suspended in 200 mL deionised http://dx.doi.org/10.1016/j.antiviral.2015.04.004 0166-3542/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Campus El Cristo, Edificio Santiago Gascón, 33006 Oviedo, Spain. Tel.: +34 985104215; fax: +34 985103157. E-mail address: alvarezrangel@uniovi.es (Á.L. Álvarez). 1 Present address: Zoology and Entomology Department, Faculty of Science, Helwan University, Cairo 11795, Egypt. Antiviral Research 119 (2015) 8–18 Contents lists available at ScienceDirect Antiviral Research journal homepage: www.elsevier.com/locate/antiviral