Abstract
Tannins, plant-derived polyphenols and other related compounds, have been utilized for a long time in many fields such as the food industry and manufacturing. In this study, we investigated the anti-viral effects of tannins on 12 different viruses including both enveloped viruses (influenza virus H3N2, H5N3, herpes simplex virus-1, vesicular stomatitis virus, Sendai virus and Newcastle disease virus) and non-enveloped viruses (poliovirus, coxsachievirus, adenovirus, rotavirus, feline calicivirus and mouse norovirus). We found that extracts from persimmon (Diospyros kaki), which contains ca. 22% of persimmon tannin, reduced viral infectivity in more than 4-log scale against all of the viruses tested, showing strong anti-viral effects against a broad range of viruses. Other tannins derived from green tea, acacia and gallnuts were effective for some of the viruses, while the coffee extracts were not effective for any of the virus. We then investigated the mechanism of the anti-viral effects of persimmon extracts by using mainly influenza virus. Persimmon extracts were effective within 30 seconds at a concentration of 0.25% and inhibited attachment of the virus to cells. Pretreatment of cells with the persimmon extracts before virus infection or post-treatment after virus infection did not inhibit virus replication. Protein aggregation seems to be a fundamental mechanism underlying the anti-viral effect of persimmon tannin, since viral proteins formed aggregates when purified virions were treated with the persimmon extracts and since the anti-viral effect was competitively inhibited by a non-specific protein, bovine serum albumin. Considering that persimmon tannin is a food supplement, it has a potential to be utilized as a safe and highly effective anti-viral reagent against pathogenic viruses.
Highlights
Animal viruses, which are causative agents of human and animal diseases, can be divided into two types based on their physical properties: enveloped virus, which has a viral envelope composed of a lipid bilayer on its surface, and non-enveloped virus, which lacks an envelope with its protein shell usually being exposed to the environment [1,2].Influenza virus, an enveloped virus, is a pathogen that causes respiratory infection
We investigated the effects of seven extracts and chemical compounds containing tannins against twelve enveloped and non-enveloped viruses, and we found that persimmon extracts alone inactivated all of the viruses
Cytotoxicity of tannins to cultured cells Cultured cells used in this study for anti-virus tests, MDCK(+), FL, LLC-MK2, Vero, MA104, CRFK and RAW264.7 cells (Table 2), were individually incubated with the seven tannin samples, Persimmon extracts (PE), Wattle extracts (WE), CE, Green tea extracts (GTE), Pentagalloyl glucose (PGG), PRG and PYG (Table 1), for
Summary
Animal viruses, which are causative agents of human and animal diseases, can be divided into two types based on their physical properties: enveloped virus, which has a viral envelope composed of a lipid bilayer on its surface, and non-enveloped virus, which lacks an envelope with its protein shell usually being exposed to the environment [1,2]. An enveloped virus, is a pathogen that causes respiratory infection. Influenza virus is sensitive to detergents or ethanol-based reagents. A non-enveloped virus, is a causative agent of acute gastroenteritis, affecting many people all over the world [4]. Human norovirus is generally resistant to usual detergents as well as ethanol-based reagents, causing difficulty in sanitation [4]
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