ANTIOXIDANT ACTIVITY OF PHENOLIC EXTRACTS OF EVENING PRIMROSE (OENOTHERA BIENNIS): A PRELIMINARY STUDY

Phenolic compounds from ethanolic extracts of evening primrose ( Oenothera biennis ) were separated into ten fractions using Sephadex LH-20 column chromatography. For individual fractions, UV spectra were recorded and the content of total phenolics determined. Antioxidant activity of each isolated fraction was examined in a β-carotene-linoleate model system. Fractions were further characterized for the number of phenolic compounds, presence of proanthocyanidins and their antioxidant activity by TLC analysis. Strong antioxidant properties were noted for fractions with high content of total phenolics (fractions IV-X). Vanillin-positive compounds were observed in fractions VI-X and one compound was tentatively identified as (+)catechin/(−)epicatechin. From fraction IV, two phenolic compounds were separated by preparative TLC; compound A was most likely an isoflavone and the UV spectrum of compound B was similar to that of 2-hydroxychalcone.