Propolis extraction methods: a review

Propolis (bee glue) is a sticky material collected by bees from plant resins, it has been proven to possess numerous beneficial pharmacological properties: antibacterial, antiviral, antioxidant, antiinflammatory, immunostimulating, hepatoprotective, cytotoxic, etc. Nowadays, propolis is a popular remedy all over the world, and is available in either pure form or combined with other natural products in over-the-counter preparations, cosmetics, and as a constituent of health foods. The interest in propolis containing commercial products is steadily growing. The extraction is a key step in making use of the bioactive constituents of propolis. The present review summarizes and discusses the available data about classical and modern methods of extraction of propolis with potential large-scale application. The published data concerning maceration, Soxhlet, ultrasound-assisted and microwave-assisted extraction, supercritical CO2 extraction, high-pressure methods, and the application of different solvents are discussed. Concerning the solvents, water - ethanol mixtures remain among the most effective, oil and natural deep eutectic solvents (NADES) have demonstrated promising potential. From the extraction processes, ultrasound-assisted extraction seems to be the optimal method, taking into account extraction time and extraction yield. Of course, more studies are necessary to find the best way to extract bioactive compounds from different types of propolis, based on chemometric optimization approaches, especially with respect to large-scale application.