INFLUENCE OF SOLVENT ON YIELD, COMPOSITION OF EXTRACTED COMPUNDS AND ANTIOXIDANT ACTIVITY OF PROPOLIS EXTRACTS

Propolis, a multifunctional material produced by bees, is one of the richest natural sources of flavonoids and other phenolic antioxidants. In this work we have investigated yield, composition (total phenol and flavonoid content) and antiradical activity (DPPH radical scavenging) of propolis extracts prepared using different mixture of solvents (ethanol, acetone, water and ethyl acetate). For each solvent mixture, three independent extractions were performed. The results show that the increase of solvent lipophilicity results in increase of extraction yield. The amount of total polyphenols decreases linearly with the increase of water in the extraction solvent (r2= 0.93 and 0.97 for ethanol and acetone, respectively). The content of flavonoids remains relatively constant at higher concentration of water and rises steeply when the amount of aceton or ethanol reaches 80%. It is interesting to note that addition of small amount of ethyl acetate to water/ethanol mixture results in significant increase of total phenols and flavonoids in the extract. Radical scavenging activity, assayed with DPPH free radical, was dependent on the amount of total phenols in the extract. HPLC analysis has revealed presence of several phenolic acids and flavonoids in the extracts such as p-coumaric acid, pinocembrine and galangine, which could explain strong radical scavenging properties of the extracts. The results show that solvent used for propolis extraction strongly affects chemical composition and activity of propolis extracts.