A method of producing a substance with antimicrobial, antiviral, and immunostimulatory activities, particularly towards dendritic cells is proposed, provides for using the chopped potato sprouts as plant raw materials are extracted with water, then the aqueous extract is centrifuged, a salt agent is added, and the obtained saline solution is then concentrated using ultrafiltration through a 300-kD filter, then the solution is frozen for 24 hours, thawed, and filtered, and the pellet thus obtained is removed, and the raw peptidoglycan is precipitated from the solution by using an acidic salt agent and is further re-solubilized with alkali, then the alkaline solution is dialyzed against distilled water on a 12 kD filter, and the peptidoglycan having a molecular weight of 500 kD to 17000 kD is purified from the resulting solution using gel permeation chromatography.