Supercritical fluid extractive fractionation – study of the antioxidant activities of propolis

Propolis was mixed with ethanol at a ratio of 1:10 (v/w) for 24 h to yield propolis ethanol extract (E). Extract E was further fractionated with supercritical carbon dioxide (SC-CO2) into four fractions (R, F1, F2 and F3). To evaluate the selectivity of the fractionation, extracts corresponding to four fractions were characterized in terms of total flavonoid contents, antioxidant abilities and antioxidant mechanisms. Experimental results indicated that fractionation altered the composition distributions of fractions, e.g., by reducing total flavonoid contents. The antioxidant ability, metal chelating capacity, reducing power, and scavenging capacity of DPPH, O2·−or ·OH radicals of propolis extract and fractions increased with propolis concentrations. The effects of scavenging on DPPH of propolis extract and fractions, at 2 mg/ml were R (93%), E (75%), F1 (56%), F2 (47%), and F3 (27%). At a concentration of 1 mg/ml, propolis fractions scavenged O2·− by over 73% and all the fractions trapped around 65% of the ·OH groups. This in vitro study of antioxidant effects showed that R and F1 were the best fractions, followed by F2.