PROBLEM TO BE SOLVED: To provide a new component effective for herpes simplex virus infection preventive/therapy with Grifola frondosa, an extraction/purification method thereof, search for effective action, and also use as an external preparation.SOLUTION: An extracted fraction of Grifola frondosa, which is produced by the steps of (1) heat-extraction treating a mycelium or a fruit body of Grifola frondosa with water, (2) adding alcohol to the resulting extracted water-soluble fraction to give a final volume concentration of 20 to 70%, leaving to stand at a temperature of 1 to 25°C and removing a substance suspending on the liquid surface or in the liquid or adhering on the wall surface of a container, and (3) removing alcohol in the resulting extract liquid and collecting the dried substance, is effective for herpes simplex virus infection prevention/therapy.
