Supercritical Antisolvent Fractionation of Propolis Tincture

Propolis is used by bees for holding a hive together, and for sterilizing the hive against microbial infections. Propolis contains a high concentration of flavonoids, which are used in a wide range of cosmetic and health food preparations for their antimicrobial properties. Propolis is usually dissolved in ethanol or ethanol/water mixtures to produce a tincture, and to remove insoluble material such as waxes and detritus from the hive. A new supercritical antisolvent/extraction process has been developed for the fractionation of propolis tincture to increase the concentration of flavonoids and remove high molecular mass components and the essential oil. Flavonoids are practically insoluble in pure CO2, but sufficiently soluble in CO2 + ethanol to enable their separation from high molecular mass and/or more polar components. In the first step of the process, supercritical CO2 is used both as an anti-solvent to precipitate high molecular mass components (and water), and as a solvent to extract the ethanol and soluble components of the propolis. This extract is then fractionated in two separation steps to give a concentrated flavonoid fraction as the main product, and an essential oil/ethanol fraction as a secondary product. The effects of pressure, temperature, flow rate ratio, tincture composition and concentration on product quality and yield were determined at a laboratory and pilot scale. The tincture concentration of Propolis, and tincture composition has the greatest effect on the yield and concentration of flavonoids in the product fraction.