Three commercial products of herbal extracts (Amphiflu-Ex®, Fyto-immune Plus® and Viu-Vet®) were tested for antiviral activity against two Egyptian highly pathogenic avian influenza subtype H5N1 isolates (isolated form backyard poultry) and upon sequencing and phylogenetic analysis, they belonged to clade 220.127.116.11., This antiviral assay for the products done by using chicken embryo fibroblast (CEF) cell culture through cytopathic effect (CPE) inhibition assay in two different layouts to elucidate post-exposure and pre-exposure antiviral activity of the products. The Amphiflu-Ex® at conc. 50 µl/ml showed significant virucidal activity (100% inhibition) in post-exposure assay for both viral isolates which was further confirmed by quantitative real time RT-PCR method showed 100% reduction in virus titers for both isolates and further investigation done on The Amphiflu-Ex® on conc. 20 µl/ml, the virus titers were decreased by 2.72-2.8 logs (Log 10 virus titers) and on conc 10 µl/ml, the virus titers were decreased by 1-1.27 logs for both isolates, The maximum non-toxic concentration (MNTC) for the three products estimated by cytotoxicity assay was 50 µl/ml and TCID50 used for both isolates were 106 copy/100 µl.
Key words: Avian influenza virus subtype- H5N1, Antiviral activity, Herbal extracts, RT-PCR.