In vitro and in vivo anti-influenza virus activity of diarylheptanoids isolated from Alpinia officinarum.

BACKGROUND Diarylheptanoids (AO-0002 [7-(4''-hydroxy-3''-methoxyphenyl)-1-phenyl-4E-hepten-3-one] and AO-0011 [(5S)-5-hydroxy-7-(4''-hydroxyphenyl)-1-phenyl-3-heptanone]) isolated from Alpinia officinarum have been reported to exhibit anti-influenza virus activity in vitro. Hence, efficacies against influenza virus infection and the mode of antiviral action were evaluated in vivo and in vitro, respectively. METHODS In a murine influenza virus infection model, diarylheptanoids were orally administered three times daily to mice infected with influenza A/PR/8/34 virus for 6 days after infection. AO-0002 was examined for its antiviral activity against the wild types of influenza viruses A/PR/8/34 (H1N1), oseltamivir-resistant A/PR/8/34 (H1N1), A/Bangkok/93/03 (H1N1), A/Ishikawa/7/82 (H3N2), A/Fukushima/13/43 (H3N2), B/Singapore/222/79 and B/Fukushima/15/93 in plaque reduction or yield reduction assays. The mode of anti-influenza virus action was assessed by a virus adsorption assay, immunofluorescence assay of viral antigens, and inhibition of viral messenger RNA synthesis using real-time reverse transcriptase PCR. RESULTS AO-0002 at 100 mg/kg was significantly effective in reducing the body weight loss and prolonging survival times of infected mice without toxicity, but AO-0011 was not. AO-0002 at 30 and 100 mg/kg significantly reduced virus titres in bronchoalveolar lavage fluids of the lungs on days 3 and 6 after infection. AO-0002 exhibited anti-influenza virus activity against all viruses used, including the oseltamivir-resistant strain in vitro. The compound had no effect on virus adsorption or invasion into cells, but dose-dependently suppressed the expression of viral messenger RNA and antigens. CONCLUSIONS AO-0002 was suggested to have a different anti-influenza virus action to that of oseltamivir and was verified to show anti-influenza activity in vitro and in vivo.