Antioxidative and radical scavenging activities of propolis extracts in food models
Propolis samples collected from Mwingi, Malindi, Uasin-gishu and Meru south districts in Kenya were extracted using ethanol and methanol. The methanol extracts were further partitioned into ethyl acetate, hexane and aqueous fractions. The extracts were concentrated and dried in vacuum evaporator. Their antioxidative activities were tested in linoleic acid-â-carotene system and in soybean oil. The extracts’ radical scavenging activities against 2,2–diphenyl-1-picrylhydrazil (DPPH) were also
studied. Significant differences were observed between the samples as well as within the samples’ various extracts. The ethanol extract of propolis (EEP) and the ethyl acetate fractions from all four samples had higher 2,2–diphenyl-1-picrylhydrazil (DPPH) radical scavenging activity compared to the aqueous and the hexane extracts at a concentration of 500 ìg/ml. Malindi EEP at a concentration of 500 ìg/ml had a significantly (p < 0.05) higher radical scavenging activity (87.7%) than all the other EEP’s. The least radical scavenging activity was observed in Uasin-gishu EEP with
73.3%. The Mwingi ethyl acetate extract at a concentration of 500 ìg/ml had 79.2% radical scavenging activity which was the highest observed amongst the ethyl acetate fractions and the least was in Uasin-gishu sample having 66.1% activity. The highest activity among the aqueous extracts was 7.1% in Meru South sample at a concentration of 500 ìg/ml. Radical scavenging activity did not differ in all four aqueous fractions. There was no significant difference (p < 0.05) observed in the antioxidation activity of Mwingi, Meru south and Malindi EEPP’s, in the linoleic acid-â-carotene system at a concentration of 500 ìg/ml. The EEP’s were the most active against oxidation of the system with a range of 61.7% in Uasin-gishu sample to 71.8% in Malindi sample while the aqueous was the least active with a range of 5.8% to 11.7% in Uasin-gishu and Malindi samples respectively. The EEP’s at a concentration of 1mg/ml showed greater activity against antioxidation of soybean oil compared to butylated hydroxyltoluene (BHT) at a concentration of 0.2 ìg/ml for the
first 25 days of the test. After the 25th day, there was sharp increase in peroxide values in all the EEPs showing loss of antioxidation strength.
Key words: Propolis, Radical scavenging, antioxidation activity
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