Method for extracting and purifying rosmarinic acid in balm

The invention relates to a method for extracting and purifying rosmarinic acid in melissa. The method comprises the following steps: (1) taking a melissa raw material, adding the melissa raw material into a crusher, and crushing the melissa raw material to 20-40 meshes; adding water which is 6-10 times of the weight volume of the crushed raw materials into the crushed raw materials, performing reflux extraction, and filtering; (2) adding the filtrate obtained in the step (1) into a concentrator for concentration, adding ethanol of which the volume is 5-6 times that of the filtrate for alcohol precipitation, and performing solid-liquid separation to obtain filtrate; and (3) adding the filtrate obtained in the step (2) into a concentrator, concentrating again, and finally drying to obtain the rosmarinic acid. The rosmarinic acid with the content of 10% or above can be stably obtained through the two-step process of water extraction and alcohol precipitation, and the method is low in process cost and high in eff