Cosmetic composition made of a plant extract, preferably strawberry roots, is claimed. An independent claim is included for a process for preparing the plant extract with antioxidant activity as main constituent in the cosmetic composition to fight against the manifestations of the skin aging, comprising treating the strawberry roots mainly by lyophilization without chemical or biochemical treatment, which is harmful to the natural cellulose. ACTIVITY : Dermatological. MECHANISM OF ACTION : None given.