Polysaccharide extract (I) obtained from mushroom of Lentinusgenus, comprises: monosaccharides, polysaccharides, 2-8 wt.% of trehalose, 1-4 wt.% of glucose and 30-60 wt.% of alditols. An independent claim is included for a process for the preparation of (I), comprising one or more solid/liquid extraction with a part of Lentinusmushroom, precipitating the liquid extract by an organic solvent, centrifuging, filtering the precipitate and drying. ACTIVITY : Dermatological; Antipsoriatic. MECHANISM OF ACTION : None given.