Proanthocyanidin from blueberry leaves suppresses expression of subgenomic hepatitis C virus RNA

J Biol Chem. 2009 Aug 7;284(32):21165-76. doi: 10.1074/jbc.M109.004945. Epub 2009 Jun 16.


Hepatitis C virus (HCV) infection is a major cause of chronic liver disease such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma. While searching for new natural anti-HCV agents in agricultural products, we found a potent inhibitor of HCV RNA expression in extracts of blueberry leaves when examined in an HCV subgenomic replicon cell culture system. This activity was observed in a methanol extract fraction of blueberry leaves and was purified by repeated fractionations in reversed-phase high-performance liquid chromatography. The final purified fraction showed a 63-fold increase in specific activity compared with the initial methanol extracts and was composed only of carbon, hydrogen, and oxygen. Liquid chromatography/mass-ion trap-time of flight analysis and butanol-HCl hydrolysis analysis of the purified fraction revealed that the blueberry leaf-derived inhibitor was proanthocyanidin. Furthermore, structural analysis using acid thiolysis indicated that the mean degree of polymerization of the purified proanthocyanidin was 7.7, consisting predominantly of epicatechin. Proanthocyanidin with a polymerization degree of 8 to 9 showed the greatest potency at inhibiting the expression of subgenomic HCV RNA. Purified proanthocyanidin showed dose-dependent inhibition of expression of the neomycin-resistant gene and the NS-3 protein gene in the HCV subgenome in replicon cells. While characterizing the mechanism by which proanthocyanidin inhibited HCV subgenome expression, we found that heterogeneous nuclear ribonucleoprotein A2/B1 showed affinity to blueberry leaf-derived proanthocyanidin and was indispensable for HCV subgenome expression in replicon cells. These data suggest that proanthocyanidin isolated from blueberry leaves may have potential usefulness as an anti-HCV compound by inhibiting viral replication.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blueberry Plants
  • Chromatography, High Pressure Liquid
  • Chromatography, Liquid / methods
  • Drug Resistance, Viral*
  • Gene Expression Regulation, Viral / drug effects*
  • Hepacivirus / genetics*
  • Inhibitory Concentration 50
  • Mass Spectrometry / methods
  • Neomycin / pharmacology
  • Plant Extracts / metabolism*
  • Plant Leaves / metabolism*
  • Polymers / chemistry
  • Proanthocyanidins / metabolism*
  • RNA, Viral*
  • Virus Replication / drug effects*


  • Plant Extracts
  • Polymers
  • Proanthocyanidins
  • RNA, Viral
  • proanthocyanidin
  • Neomycin