Sixteen antioxidative compounds were purified and isolated from the aerial parts of Suaeda japonica by column chromatography using Amberlite XAD-2 and octadecylsilane columns and high-performance liquid chromatography. These compounds, esculin ( 1), citrusin D (2), scopolin (3), cichoriin (4), isorhamnetin 3-O-rutinoside-7-O-β-D-glucopyranoside (5), 3'-methoxytaxifolin 7-O-β-D-glucopyranoside (6), (+)-lyoniresinol 3a-O-β-D-glucopyranoside (7), (2R,3R,4S)-isolariciresinol 3a-O-β-D-glucopyranoside (8), N-cis-feruloyltyramine 4-O-β-D-glucopyranoside (9), N-cis-feruloylmethoxytyramine 4-O-β-D-glucopyranoside (10), trans-icariside H 1 (11), cis-icariside H 1 (12), N-transferuloyltyramine 4-O-β-D-glucopyranoside (13), rutin (14), kaempferol-3-O-rutinoside (15), and narcissin ( 16), were identified for the firtst time in S. japonica. The structures of these compounds were determined by mass spectrometry and nuclear magnetic resonance spectroscopic analyses. Among the compounds, 14 showed the highest 1,1-diphenyl-2-picrylhydrazyl free radical-scavenging activity and 8 exhibited the highest reactive oxygen species-scavenging activity in Huh7 cells.

Suaeda japonica is a useful candidate food material for the manufacture of blended tea due to its red color and excellent antioxidant activity. Rutin and narcissin are the main antioxidative flavonoids in the aerial parts of S.japonica, and these compounds have been reported to have antioxidant, anti-inflammatory, antibacterial, and anticancer activities. However, comparatively little is known about the biological activities of narcissin, which is present in small amounts in several plants. In this study, we developed an isolation method to obtain rutin and narcissin simultaneously in high purity from the aerial parts of S. japonica. The rutin and narcissin contents in the hot water extract of the aerial parts of S. japonica were 59.2 ± 1.3 mg/100 g and 171.3 ± 2.1 mg/100 g, respectively, as determined by ODS-HPLC. Briefly, the dried aerial parts (50 g) of S. japonica were extracted with hot water, and the filtrate obtained was extracted with water-saturated n-butanol (BuOH). The BuOH fraction was purified by medium-performance liquid chromatography using an octadecylsilane column. The purities of the rutin (27.6 mg) and narcissin (79.9 mg) isolated both exceeded 99% by LC-MS and 1 H-NMR analysis, and their total recoveries were estimated to be > 91%.