Background: Herbs were the basis for nearly all medicinal therapy until synthetic drugs were developed in the nineteenth century. The major reasons for using medicinal herbs as a good alternative to chemical drugs, is that they have fewer side effects than synthetic drugs. Objective(s): The main objectives of this study were to investigate the antiviral activity of some popular herbal extracts in Egypt, and to determine their antioxidant activity. Methods: Experimental studies were carried out in different labs of the National Research Center in Cairo, Egypt. Ethanol extracts of three herbal plants with a history of use in traditional medicine namely; Zingiber officinale (Ginger), Nigella sativa (Black seeds) and Foeniculum vulgare (fennel) were tested for their antioxidant potency and antiviral activity against influenza virus. In vitro cytotoxicity assay was made for the extracts by 3-(4, 5-dimethylthiazol-2-yl)-2, 5diphenyltetrazolium bromide (MTT) colorimetric assay for the determination of the concentration that causes inhibition to half of the viable cells (50% growth inhibition TC50) for each extract and selection of the safe concentration for the antiviral experiment. Antiviral activities were determined by Plaque reduction assay using Madin-Darby canine kidney (MDCK) cell line. Percentage of radical scavenging was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) method to evaluate the antioxidant activity of the extracted plants. Results: Each herb had a certain cytotoxic effect to MDCK cells at the different tested concentrations, TC50 calculated ranged from 50 to 308 μg/μl. The extracts inhibited the growth and development of H5N1 virus in a dose-dependent manner with varying antiviral activity. The most potent viral inhibitor was reported by ethanol extracts of Foeniculum vulgare. All the tested extracts showed high antioxidant activities with some variations ranged from 77.8 to 87.2 percentage scavenging activity at 30 minutes of incubation as determined by the DPPH assay. Conclusion: Some traditionally used medicinal plants are promising sources for potential antiviral and antioxidant compounds.

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