Abstract: In this study, Sephadex LH-20 column chromatography was used to separate and purify six polyphenol fractions from adlay. The Folin-Ciocalteu method was used for the determination of the total phenolic content in each fraction. Three different antioxidant assays namely, oxygen radical absorbance capacity (ORAC), peroxyl radical scavenging capacity (PSC) and cellular antioxidant activity (CAA) were carried out to evaluate antioxidant capacity of six fractions. Among these, three fractions (Ⅱ, Ⅲ and V) with the strongest antioxidant activity were purified by semi-preparative HPLC to obtain four polyphenol compounds, whose antioxidant activity was investigated. The results indicated that polyphenols were mainly distributed in fraction Ⅱ, Ⅲ and V, with total phenolic contents of (30.56 ± 2.25), (17.40 ± 2.76) and (25.18 ± 1.10) mg GAE/100 g md. It was also found that bound phenolic compounds accounted for more than one third of the total phenolics in adlay. The purified phenolics were identified as N1,N5-double (p-coumaroyl) spermine, p-coumaric acid, ferulic acid and rutin, with N1,N5-double (p-coumaroyl) spermine being the major free phenolic compound and ferulic acid being the major bound one, which also existed in a small quantity in the bound form. All these phenolics were the main active compounds responsible for the strong antioxidant activity of polyphenols from adlay.

Key words: adlay, polyphenols, isolation, antioxidant activity