Disclosed is a root extract from plants of the Morus genus (in particular Morus albaet, Morus nigra) that is rich in prenylated polyphenols chosen from: moracenin A, moracenin B, kuwanon C, wittiorumin F and mulberrofuran T, a method for preparing such an extract and a cosmetic composition and a pharmaceutical or nutraceutical composition, the compositions including, as the active ingredient, at least one root extract from plants of the Morus genus according to the invention.