Three new diarylheptanoids and one new monoterpenoid were isolated from the rhizomes of Zingiber officinale together with four known diarylheptanoids, 5-8. Their structures were elucidated mainly by spectroscopic methods, and they were deduced as 5-[4-hydroxy-6-(4-hydroxyphenethyl)tetrahydro-2 H-pyran-2-yl]-3-methoxybenzene-1,2-diol (1), sodium (E)-7-hydroxy-1,7-bis(4-hydroxyphenyl)hept-5-ene-3 S-sulfonate (2), sodium (E)-7-hydroxy-1,7-bis(4-hydroxyphenyl)hept-5-ene-3 R-sulfonate (3), and hydroxycineole-10-O-beta-D-glucopyranoside (4), respectively. Among the isolated compounds, compounds 1, 5, and 8 exhibited strong superoxide anion radical scavenging activities in a phenazine methosulfate-NADH system. In a more biological system, these compounds were demonstrated to exhibit potent protection against lipid peroxidation in mouse liver microsomes exposed to oxidative conditions. These compounds were subsequently tested on primary cultures of rat hepatocytes exposed to oxidative damage, and definitive cytoprotective actions were found.

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After an initial clean-up step on silica gel, a preparative high-speed counter-current chromatography coupled with on-line high-performance liquid chromatography-diode array detection method (HSCCC-HPLC-DAD) was successfully developed for the isolation and determination two polymethoxylated flavones, 3',4',7-trimethoxyquercetin and artemetin, from the aerial part of Taraxacum mongolicum. The HSCCC separation was performed with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (6:5:6:5, v/v/v/v) at a flow rate of 1.5 mL/min and at 800 rpm. The on-line purity monitoring of a representative aliquot from each HSCCC fraction was operated automatically. Using this method, fractions with high purity were collected. The HSCCC purification step was done in 5 h, and afforded 84.2 mg of 3',4',7-trimethoxyquercetin and 52.3 mg of artemetin, with purity over 98% from 200 mg of the enriched extracts of T. mongolicum. The structures were identified by electorspray ionization mass spectrometry and 1H NMR experiments. To our best knowledge, 3',4',7-trimethoxyquercetin was obtained from the plant of genus Taraxacum for the first time by our group. This hyphenated method could be used for the preparation of bioactive compounds with higher purity from natural products.

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An online rapid screening method, the high-performance liquid chromatography (HPLC)-diode array detector (DAD)-radical scavenging detection (RSD)-electrospray ionization (ESI)-mass spectroscopy (MS)/MS system, was developed for the screening and identification of radical scavengers from Neo-Taraxacum siphonanthum, a new species found in China in 1989. For further characterization, the target compounds were isolated by silica column chromatography, preparative high-performance liquid chromatography (HPLC), HSCCC, and Sephadex LH-20 column chromatography and elucidated on the basis of ultraviolet (UV), ESI-MS/MS, and nuclear magnetic resonance (NMR) spectroscopy, as well as the chemical analysis. Eighteen antioxidative polyphenols (5 caffeic acid derivatives and 13 flavonoid derivatives) were characterized from Neo-T. siphonanthum. The distribution of all compounds was discussed in a chemosystematic context, which suggested that the genera Neo-Taraxacum and Taraxacum might relate chemosystematically.