Preclinical in vitro activity of QR-435 against influenza A virus as a virucide and in paper masks for prevention of viral transmission

Am J Ther. Sep-Oct 2007;14(5):455-61. doi: 10.1097/MJT.0b013e3180a6f9c2.


Prophylaxis against influenza is difficult, and current approaches against pandemics may be ineffective because of shortages of the two proven classes of antivirals in the face of a large-scale infection. Herbal/natural products may represent an effective alternative to conventional attempts to protect against infection by avian influenza virus. QR-435, an all-natural compound of green tea extract and other agents, has been developed to provide protection against a wide range of viral infections. The antiviral activities of several QR-435 preparations as well as QR-435 (1) green tea extract were tested against A/Sydney/5/97 and A/Panama-Resvir 17 strains of avian influenza virus H3N2 by means of an assay based on Madin-Darby canine kidney cells. Toxic effects of QR-435 formulations on these cells were also evaluated as were the virucidal properties of a commercially available mask impregnated with QR-435. The efficacy of a QR-435/mask combination was compared with that of the QR control/mask combination, an untreated mask, and no mask. QR-435 had significant in vitro activity against H3N2 at concentrations that were not associated with significant cellular toxic effects. The antiviral activity of QR-435 (1) was similar to that of QR-435. Masks impregnated with QR-435 were highly effective in blocking the passage of live H3N2 virus. These preclinical results warrant further evaluation of the prophylactic use of QR-435 against viral infection in humans.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antiviral Agents / administration & dosage
  • Antiviral Agents / pharmacology*
  • Antiviral Agents / toxicity
  • Combined Modality Therapy
  • Dogs
  • Dose-Response Relationship, Drug
  • Drug Evaluation, Preclinical
  • Humans
  • Infection Control / methods
  • Influenza A Virus, H3N2 Subtype / drug effects*
  • Influenza, Human / prevention & control
  • Kidney / cytology
  • Masks
  • Paper
  • Plant Extracts / administration & dosage
  • Plant Extracts / pharmacology*
  • Plant Extracts / toxicity
  • Tea / chemistry
  • Toxicity Tests


  • Antiviral Agents
  • Plant Extracts
  • Tea