title: Anti-influenza activity of marchantins, macrocyclic bisbibenzyls contained in liverworts.
abstract: The H1N1 influenza A virus of swine-origin caused pandemics throughout the world in 2009 and the highly pathogenic H5N1 avian influenza virus has also caused epidemics in Southeast Asia in recent years. The threat of influenza A thus remains a serious global health issue and novel drugs that target these viruses are highly desirable. Influenza A possesses an endonuclease within its RNA polymerase which comprises PA, PB1 and PB2 subunits. To identify potential new anti-influenza compounds in our current study, we screened 33 different types of phytochemicals using a PA endonuclease inhibition assay in vitro and an anti-influenza A virus assay. The marchantins are macrocyclic bisbibenzyls found in liverworts, and plagiochin A and perrottetin F are marchantin-related phytochemicals. We found from our screen that marchantin A, B, E, plagiochin A and perrottetin F inhibit influenza PA endonuclease activity in vitro. These compounds have a 3,4-dihydroxyphenethyl group in common, indicating the importance of this moiety for the inhibition of PA endonuclease. Docking simulations of marchantin E with PA endonuclease suggest a putative "fitting and chelating model" as the mechanism underlying PA endonuclease inhibition. The docking amino acids are well conserved between influenza A and B. In a cultured cell system, marchantin E was further found to inhibit the growth of both H3N2 and H1N1 influenza A viruses, and marchantin A, E and perrotein F showed inhibitory properties towards the growth of influenza B. These marchantins also decreased the viral infectivity titer, with marchantin E showing the strongest activity in this assay. We additionally identified a chemical group that is conserved among different anti-influenza chemicals including marchantins, green tea catechins and dihydroxy phenethylphenylphthalimides. Our present results indicate that marchantins are candidate anti-influenza drugs and demonstrate the utility of the PA endonuclease assay in the screening of phytochemicals for anti-influenza characteristics.
authors.affiliation: Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima, Japan.
authors.forename: Yuma
authors.initials: Y
authors.lastname: Iwai
authors.forename: Kouki
authors.initials: K
authors.lastname: Murakami
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Gomi
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Asakawa
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Okuno
authors.forename: Toyokazu
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Dai
authors.initials: D
authors.lastname: Hatakeyama
authors.forename: Noriko
authors.initials: N
authors.lastname: Echigo
authors.forename: Takashi
authors.initials: T
authors.lastname: Kuzuhara
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D003198:Computer Simulation; D004285:Dogs; D004720:Endonucleases / Q000378:metabolism; D035926:Hepatophyta / Q000737:chemistry*; D053118:Influenza A Virus, H1N1 Subtype / Q000187:drug effects*; D053122:Influenza A Virus, H3N2 Subtype / Q000187:drug effects*; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000821:virology; D047028:Macrocyclic Compounds / Q000494:pharmacology*; D009976:Orthomyxoviridae Infections / Q000188:drug therapy*; D008517:Phytotherapy
chemical_list: D000998:Antiviral Agents; D047028:Macrocyclic Compounds; D004720:Endonucleases