A method is described for the extraction of products having a pharmacological activity, in particular an immunomodulating activity, from spermatophyte plants. Said products, which are to be used in the pharmaceutical fields, consist of complex mixtures of compounds characterized by one or more stilbene groups, variously hydroxylated and / or glucosidated, and of compounds derived from said group by natural enzymatic biosynthetical processes (stilbenoids). The following compounds are preferred: T-Res, C-Res, glucosidated C-Res, epsilon-viniferine, H-gnetine, r-2-viniferine, r-vinifezine, hopeaphenol, Ampelopepsin A and glucosidated T-Res.