title: Probing the impact of quercetin-7-O-glucoside on influenza virus replication influence.
abstract: BACKGROUND
  Influenza virus is still at large and seriously affects social welfare and health. Dianthus superbus is a well-known medicinal plant widely used in Mongolian and Chinese traditional medicine for anti-inflammatory purposes.
  
  
  OBJECTIVE
  To investigate the influence of this novel herbal medicinal product over virus infection and virus-induced symptoms
  
  
  METHODS
  Quercetin-7-O-glucoside was isolated by bioassay (anti-influenza)-guided fractionation. The structural elucidation was made with 1H-NMR and 13C-NMR. Influenza A/Vic/3/75 (H3N2), A/PR/8/34 (H1N1), B/Maryland/1/59 and B/Lee/40 viruses were used for the evaluation of the antiviral activity. Virus-induced reactive oxygen species and autophagy formation levels were studied. The antiviral mechanism was elucidated via time-dependent, pre-, post-incubation assay methods. The viral RNA replication inhibition of Q7G was analyzed using quantitative RT-PCR method. The blocking of polymerase basic protein subunits of influenza viral RNA polymerase by Q7G was detected by in silico molecular docking assays using AutoDock Vina program with m(7)GTP. Additionally, Q7G was tested against M-MuLV RNA polymerase.
  
  
  RESULTS
  Q7G was not cytotoxic (CC50>100µg/ml) in MDCK cells and it showed 3.1µg/ml, 6.61µg/ml, 8.19µg/ml and 5.17µg/ml IC50 values against influenza A/PR/8/34, A/Vic/3/75, B/Lee/40 and B/Maryland/1/59 virus strains, respectively. Treatment of Q7G highly reduced ROS and autophagy formation induced by influenza virus infection. Q7G did not reduce NA activity and did not directly interact with the virus particles. Since viral RNA synthesis was blocked by treatment of Q7G. We targeted viral RNA polymerase for further probing. Interestingly, the binding energy of Q7G on viral PB2 protein was -9.1kcal/mol and was higher than m(7)GTP recorded as -7.5kcal/mol. It also was observe to block M-MuLV RNA polymerase.
  
  
  CONCLUSIONS
  Isolated compound Q7G showed strong inhibition activity against influenza A and B viruses. It also reduced virus-induced ROS and autophagy formation. Q7G does not directly bind to the virus particles and did not affect NA activity. These results indicated that Q7G inhibits viral RNA polymerase, and that it occupies the binding site of m(7)GTP on viral PB2 protein.
authors.affiliation: Department of Bio-resources and Food Science, Konkuk University, Seoul 143-701, South Korea.
authors.forename: Enkhtaivan
authors.initials: E
authors.lastname: Gansukh
authors.affiliation: Department of Bio-resources and Food Science, Konkuk University, Seoul 143-701, South Korea.
authors.forename: Zakayo
authors.initials: Z
authors.lastname: Kazibwe
authors.affiliation: Department of Bio-resources and Food Science, Konkuk University, Seoul 143-701, South Korea.
authors.forename: Muthuraman
authors.initials: M
authors.lastname: Pandurangan
authors.affiliation: Department of Bio-resources and Food Science, Konkuk University, Seoul 143-701, South Korea.
authors.forename: Gopal
authors.initials: G
authors.lastname: Judy
authors.affiliation: Department of Bio-resources and Food Science, Konkuk University, Seoul 143-701, South Korea.. Electronic address: kimdh02@hanmail.net.
authors.forename: Doo Hwan
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology*; D001343:Autophagy / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D029749:Dianthus / Q000737:chemistry; D005960:Glucosides / Q000494:pharmacology*; D006801:Humans; D009980:Influenza A virus / Q000187:drug effects; D009981:Influenza B virus / Q000187:drug effects; D062105:Molecular Docking Simulation; D009439:Neuraminidase / Q000037:antagonists & inhibitors; D009975:Orthomyxoviridae / Q000187:drug effects*; D010936:Plant Extracts / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry; D011794:Quercetin / Q000031:analogs & derivatives* / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D000998:Antiviral Agents; D005960:Glucosides; D010936:Plant Extracts; D017382:Reactive Oxygen Species; C089996:quercimeritrin; D011794:Quercetin; D009439:Neuraminidase
keywords: Autophagy; Dianthus superbus; Influenza virus; Viral PB2 subunit; Virus induced ROS