Antioxidant activities of different extracts and homoisoflavanones isolated from thePolygonatum odoratum

The antioxidant activities of five extracts from Polygonatum odoratum rhizomes were measured by three antioxidant assays in vitro. The crude flavonoid extracts (FE) exhibited the strongest antioxidant activity among all extracts with IC(50/DPPH) = 0.06 ± 0.035 mg mL(-1), IC(50/OH) = 0.68 ± 0.030 mg mL(-1) and reducing power/Abs125 µg mL(-1) = 0.56 ± 0.033, respectively. In order to identify functional antioxidants, two C-methylated homoisoflavanones were isolated and purified from FE and their structures were identified by spectrometric techniques as 3-(4'-hydroxy-benzyl)-5,7-dihydroxy-6-methyl-8-methoxy-chroman-4-one (1) and 3-(4'-hydroxyl-benzyl)-5,7-dihydroxy-6-methyl-chroman-4-one (2). Based on the results, both compounds had significant antioxidant activities on DPPH radical and reducing power but no effect on hydroxyl radical. The antioxidant activity of compound 1 (IC(50/DPPH) = 5.90 ± 0.150 µg mL(-1)) was nearly twofold stronger than compound 2 (IC(50/DPPH) = 11.64 ± 0.296 µg mL(-1)), and there was no significant difference between compound 1 and rutin (IC(50/DPPH) = 5.79 ± 0.140 µg mL(-1)).