A new anti-Helicobacter pylori juglone from Reynoutria japonica.

A 70% ethanol extract from the root portion of Reynoutria japonica afforded one new and three known juglone derivatives, namely, 2-methoxy-6-acetyl-7-methyljuglone (1), 2-ethoxy-6-acetyl-7-methyljuglone (2), 2-methoxy-7-acetonyljuglone (3), and 3-acetyl-7-methoxy-2-methyljuglone (4) together with two phenolics (5 and 6), an anthraquinone (7), a stilbene (8) and a phthalide (9). Their structures were elucidated on the basis of comprehensive spectroscopic studies including IR, MS, and 1H, 13C, 2D NMR spectra. Compound 3 is a new compound in nature, and compounds 4-6 have been isolated for the first time from R. japonica. The isolates were evaluated for their antibacterial activity against three strains (43504, 51, and 26695) of Helicobacter pylori. The four isolated juglone derivatives (1-4) showed potent growth inhibitory activity. Among them, compounds 1-3 exhibited stronger inhibitory activity than those of the positive controls, juglone and metronidazole, for the three strains and that of another reference, clarithromycin, for the 43504 and 51 strains. Specifically, the new juglone compound 3 displayed the most potent antibacterial activity against all three strains, 43504, 51, and 26695, with MIC values of 0.06, 0.06 and 0.13 µM, respectively, and MIC50 values of 0.14, 0.11 and 0.15 µM, respectively.

Large volume stacking using an EOF pump in NACE-MS.

Large volume stacking using an EOF pump (LVSEP) is realized for CE with ESI-MS. In LVSEP of anions, the adverse effects of a long sample matrix plug were overcome by pumping the plug out of the separation capillary to the inlet vial using the EOF under a potential of reverse polarity. Therefore, it was necessary to supply a backup run buffer from the outlet end of the capillary, which was not trivial in most ESI-MS configurations. We solved this difficulty simply by placing a vial supplying a backup run buffer during the matrix removal and sample stacking process. In addition, methanol was used as the run buffer solvent enabling a bare fused-silica capillary to meet the requirement of suppressed EOF. This LVSEP CE/ESI-MS has been successfully applied to six anionic analytes, achieving 400-fold enrichment in the detection sensitivity by using a conventional sheath liquid CE/ESI-MS interface without any physical modification.

Large-volume stacking in capillary electrophoresis using pH hysteresis of the electroosmotic flow in a bare fused-silica capillary.

For large-volume stacking with the electroosmotic flow pump (LVSEP) in capillary electrophoresis of anionic analytes it is required that the electroosmotic mobility (EOM) should be smaller than the magnitudes of the effective mobilities of the analytes. When a fused-silica capillary is treated with an acidic solution, the silanoate group on the silica surface is neutralized to silanol and the EOM is suppressed. Due to the slow deprotonation equilibrium of the silanol group at an intermediate pH, this reduced EOM can be retained during a number of electrophoresis runs. Using a bare fused-silica capillary preconditioned with 0.01 M HCl, successful LVSEP at pH 6.0 was achieved for weakly acidic compounds with two orders of magnitude enhancements in the concentration sensitivity. The repeatability in migration times of ten analytes stacked by LVSEP in a single day was excellent with the relative standard deviation (RSD) less than 1% (n = 6). The day-to-day repeatability was also excellent with RSD less than 3% (n = 3 x 6) when the capillary was preconditioned each day.