Methods for obtaining an extract enriched in rosmarinic acid from fresh plant material selected from the fresh aerial parts, flowering tops, flowers and/or leaves of plants from the family Lamiaceae, Araliaceae, Boraginaceae, Apiaceae, Poaceae and Malvaceae. The methods include steam bleaching the plant material followed by continuous expression with at least one compression screw, under pressure of between 4 and 10 bar from which the sap (liquid co-product) is recovered. Then, the sap is filtered to produce a clarified sap and is subsequently atomized to obtain a granulated or finely powdered extract containing at least 5% of rosmarinic acid in weight relative to the total weight of the extract. Compositions having such an extract as an active agent are disclosed. The compositions are used in the food, cosmetic, nutraceutical and pharmaceutical fields.