172 Copyright by authors. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Folia Medica 62(1): 172-9 DOI: 10.3897/folmed.62.e49370 Antiviral, Cytotoxic and Antioxidant Effects of Tanacetum Vulgare L. Crude Extract In Vitro Neli Vilhelmova 1 , Lora Simeonova 1 , Nadya Nikolova 1 , Elitsa Pavlova 2 , Zlatina Gospodinova 3 , Georgi Antov 3 , Angel Galabov 1 , Ivanka Nikolova 1 1 Te Stephan Angelof Institute of Microbiology, Sofa, Bulgaria 2 Faculty of Physics, St Kliment Ohridski University of Sofa, Sofa Bulgaria 3 Institute of Plant Physiology and Genetics, Sofa, Bulgaria Corresponding author: Ivanka Nikolova, Te Stephan Angelof Institute of Microbiology, Sofa, 26 Georgi Bonchev St., Sofa 1113, Bulgaria, E-mail: vanianik@mail.bg Received: 13 Dec 2019 ♦ Accepted: 14 Feb 2020 ♦ Published: 31 March 2020 Citation: Vilhelmova N, Simeonova L, Nikolova N, Pavlova E, Gospodinova Z, Antov G, Galabov A, Nikolova I. Antiviral, cytotoxic and antioxidant efects of Tanacetum vulgare L. crude extract in vitro. Folia Med (Plovdiv) 2020;62(1):172-9. doi: 10.3897/folmed.62. e49370. Abstract Introduction: Due to the high prevalence of viral infections having no specifc treatment and the constant emergence of resistant viral strains, searching for efective antiviral compounds is crucial. Te present study explores in vitro the antiviral activity of ethanolic extract from aerial parts of Tanacetum vulgare L. against viral strains of three taxonomic groups, including agents that cause socially signifcant diseases in humans for which antiviral chemotherapy is indicated, namely coxsackievirus B1 (family Picornaviridae), herpes simplex virus type 1 (family Herpesviridae) and infuenza A virus (family Orthomyxoviridae). Aim: Te aim of the current study was to evaluate antiviral activity of ethanolic extract from herbaceous plant Tanacetum vulgare L. against some important human viruses for which antiviral chemotherapy is needed and to characterize extract for its antioxidant activ- ity in vitro. Materials and methods: Te crude aqueous ethanolic extract from aerial parts of Tanacetum vulgare L. contained favonoids de- termined as apigenin, coumarins determined as aesculin, tannic compounds determined as tannin, and others. Antiviral activity of ethanolic extract from herbaceous plant Tanacetum vulgare L. against coxsackievirus B1, infuenza A and herpes simplex virus type 1 was evaluated by viral yield reduction technique. Te total antioxidant activity was determined by measuring the capacity of the sample to inhibit the generation of thiobarbituric acid reactive substances (TBARS). Results: Te results show that the extract has the lowest toxicity on the MDBK cell line and similar cytotoxicity in Hep-2, whereas in the MDCK cells it has more than twice the highest toxicity. Testing the antiviral activity of Tanacetum vulgare L. extract revealed a slight inhibition of replication of HSV-1 with a selective index of 7.07 and IAV/H3N2 (SI = 3.69) but no specifc antiviral efect against CVB1 replication was found. Te evaluation of the antioxidant activity showed great antioxidant activity of the ethanolic extract from T. vulgare – 26 mmol/l for the applied 20 mg/ml extract. Conclusion: Te crude extract from aerial parts of the medicinal plant Tanacetum vulgare L. demonstrated low cytotoxicity in Hep-2, MDBK and moderate cytotoxic efects in MDCK cells. It exerted signifcant antiviral activity against HSV-1 as determined by the re- corded inhibition of viral replication, the blockage of virus entry - absorption stage and direct virucidal efects on extracellular virions. Te observed efect when testing Tanacetum’s extract on infuenza A H3N2 virus infection in vitro was milder, which probably resulted from the interference with the cellular pathways involved in the replication cycle. Te presence of virucidal and adsorption-suppressing activity but the absence of viral replication inhibitory efects against CBV-1 suggests a possible interaction of the extract’s components with viral capsid proteins or related cell receptors. Keywords antioxidant activity, CVB1, H3N2, HSV-1, Tanacetum vulgare L. Original Article