Mini review: Application of supercritical carbon dioxide in extraction of propolis extract

Propolis is a resinous substance produced by bees functioned to seal holes, exclude draught, protect against contamination and external intruders inside their hives has been substantially studied and reported to have numerous health properties such as antiseptic, antifungal, antibacterial, antiviral, anti-inflammatory and antioxidant characteristics. Propolis cannot be utilized as raw material, due to its complex mixture of compounds. Hence it must be separated by the extraction process. Extraction targets to removes the inert compounds in the propolis sample and preserves the flavonoids and polyphenolic fraction. The most common technique used in propolis extraction is solvent extraction that involves the use of solvents such as ethanol, water, hexane, ethyl-acetate and chloroform. However, this conventional technique has some drawbacks including strong residual flavour, possible adverse reactions, harmful to the environment, low quality of the extract and long process period requirement. Supercritical carbon dioxide (SC-CO2) is one of the alternative techniques to conventional extraction that was reported to be an excellent method to purify and fractionate bioactive compounds from natural sources. SC-CO2 extraction was first introduced for analytical application because of the demand to reduce organic solvent utilization in a laboratory environment. It has now become a favourite technique in extraction, fractionation, refinement, and deodorization of natural sample matrices in laboratory scale and industrial scale. Carbon dioxide is an ideal supercritical solvent due to its non-toxic, non-polluting, non-flammable, recoverable and environmentally benign properties. Therefore, this mini review aims to discuss the application of supercritical carbon dioxide extraction specifically on propolis sample starting with a brief introduction on propolis, methods of propolis extraction, the principle of SC-CO2 extraction, application of SC-CO2 in propolis extraction, advantages of SC-CO2 extraction and lastly comparison between SC-CO2 and conventional extraction techniques.