Antioxidant compounds and activities of methanolic extracts from steam-dried Allium hookeri root

This study was carried out to investigate the effects of steam-drying on antioxidant compounds and antioxidant activity of Alliun hookeri root (AHR). The yield of methanolic extracts, total phenolic content (TPC), browning intensity (280 nm and 420 nm), and organosulfur compound contents (alliin and cycloalliin) in raw and steam-dried AHRs were 10.71∼37.40%, 15.53∼36.36 μg/mg, 0.48∼2.09, 0.01∼0.25, 1.46∼700.61 μg/mg, and 1,173.95∼2,182.60 μg/mg, respectively. Yield, TPC, and browning intensity of AHRs increased by steam-drying, whereas organosulfur compound contents decreased. Of all methanolic extracts from raw and steam-dried AHRs, four-time steam-drying showed the lowest EC₅₀ values (0.43, 7.53, 0.34, and 0.48 mg/mL, respectively) for DPPH radical scavenging activity, ABTS radical scavenging activity, SOD-like activity, and reducing power, whereas four-time steam-drying resulted in the highest TPC (36.36 μg/mg) and browning intensity (2.09 and 0.25 at 280 and 420 nm, respectively). The antioxidant activities of methanolic extracts from raw and steam-dried AHRs were closely correlated with their TPC, browning intensity, and organosulfur compound content, showing correlation determination coefficient (R²) values higher than 0.82. As a result, four-time steam-drying of AHRs could be useful as potential antioxidant sources.