Abstract

The methanolic extract of Olea ferrugenia Royale was dissolved in distilled water and partitioned with n-hexane, chloroform, ethyl acetate and n-butanol successively. The phytochemical screening of all these organic fractions and remaining aqueous fraction was carried out and then the antioxidant potential of all studied fractions was evaluated by four in vitro methods: DPPH free radical scavenging activity, total antioxidant activity, FRAP assay and ferric thiocyanate assay. Total phenolics of these organic fractions were also determined. All the fractions showed significant antioxidant potential. The results revealed that ethyl acetate soluble fraction showed highest value of percentage inhibition of DPPH radical (92.96% ± 0.13), with IC₅₀ value of (19.76 ± 0.12 µg/ml, relative to butylated hydroxytoluene (BHT), having IC₅₀ of 12.1 ± 0.92 µg/mL. This fraction also exhibited highest FRAP value (714.45 ± 2.61 µg of trolox equivalents), highest total phenolic contents (416.4.59 ± 7.73 mg of gallic acid equivalents), as well as highest value of inhibition of lipid peroxidation (57.51% ± 1.56) when compared with other fractions. However, the chloroform soluble fraction showed highest total antioxidant activity (0.9101 ± 0.03) when compared with other fractions.

Key words: Olea ferrugenia Royale, DPPH assay, total antioxidant activity, FRAP value, total phenolics, inhibition of lipid peroxidation (%).