In vitro anti-influenza virus activity of synthetic humate analogues derived from protocatechuic acid

Arch Virol. 2002;147(2):273-84. doi: 10.1007/s705-002-8319-5.


Two humic-like substances, the oxidative polymer of protocatechuic acid (OP-PCA) and humic acid inhibit the in vitro replication of influenza virus A/WSN/33 (H1N1) in Madin-Darby canine kidney (MDCK) cells at concentrations of no cytotoxicity. The 50% inhibitory concentration (IC50) for OP-PCA was 6.59 +/- 1.02 microg/ml when the compound was added at the stage of viral adsorption. When OP-PCA was added after virus adsorption, the IC50 was 53.27 +/- 8.12 microg/ml. The IC50 for humic acid was 48.61 +/- 7.32 microg/ml and 55.27 +/- 5.46 microg/ml respectively when the compound was added at the stage of viral adsorption or post-adsorption. In spite of structural resemblance of these two compounds, they exhibit different actions of anti-flu. The OP-PCA inhibits virus-induced hemagglutination and low pH-induced cell-cell fusion. Humic acid inhibits the endonuclease activity of viral RNA polymerase. The monomer of PCA shows no inhibition on influenza virus replication.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Dogs
  • Endonucleases / drug effects
  • Endonucleases / metabolism
  • Humic Substances / chemical synthesis
  • Humic Substances / chemistry
  • Humic Substances / pharmacology*
  • Hydroxybenzoates / chemistry
  • Hydroxybenzoates / pharmacology*
  • Influenza A virus / drug effects*
  • Influenza A virus / growth & development
  • Kidney / cytology
  • Oxidation-Reduction
  • Polymers / pharmacology*
  • Viral Plaque Assay
  • Viral Proteins / biosynthesis
  • Virus Replication / drug effects*


  • Humic Substances
  • Hydroxybenzoates
  • Polymers
  • Viral Proteins
  • protocatechuic acid
  • Endonucleases