Anti‐influenza Virus Activity of Extract of Japanese Wasabi Leaves Discarded in Summer

BACKGROUND: Japanese wasabi (Wasabia japonica) is now habitually used as a spice in some kinds of Japanese foods, and its pungent taste and flavor are preferred. Generally, rhizomes and winter leaves are used as a spice and for processed foods such as pickled wasabi. Since the leaf area of summer leaves is far greater than that of winter leaves, they are not used for food, and are discarded. Thus, we need to develop an effective use for summer leaves. We investigated anti-influenza virus activity in these summer leaves as a new function.RESULTS: Seventy percent ethanol extracts of leaves harvested in July exhibited a high replication inhibition rate (98% or higher) in the type A strain (AH1N1, A/shimane/48/2002), its subtype (AH3N2, Alshimane/122/2002), and type B strain (B/shimane/2/2002). The extracts of summer leaves exhibited the same anti-influenza virus activity as winter leaves, and showed a stronger activity than stems, roots, and rhizomes.CONCLUSION: A potent anti-influenza virus activity was discovered in summer leaves of Japanese wasabi. The ethanol extracts inhibited influenza virus replication regardless of the hemagglutinin antigen type. Therefore, such extracts are expected to be a promising source of a novel anti-influenza virus agent. (c) 2008 Society of Chemical Industry.