Chemical constituents of leaf of Eucommia ulmoides / 中国中药杂志

Ten compounds were isolated from the leaf of Eucommia ulmoides by means of recrystallization and chromatographic techniques such as D-101 macroporous resin, MCI resin, ODS gel, Sephadex LH-20 and Rp-HPLC. Their structures were identified by NMR spectral analyses as kaempferide 3-O-beta-D-glucoside (1), quercetin-3-O-beta-D-glucoside (2), quercetin (3), quercetin-3-O-beta-D-xylosyl-(1-->2)-beta-D-galactoside (4), kaempferol-3-O-alpha-L-rhamnosyl-(1-->6)-beta-D-glucoside (5), (2S,3S)-taxifolin 3-O-beta-D-glucoside (6) ,4-hydroxy cinnamic acid (7), (+)-cycloolivil (8), pinoresinol beta-D-glucoside (9), squalene (10). Among them compounds 1,5-7,10 were isolated from the Eucommia genus for the first time. In the DPPH free radical scavenging assay, compound 2 exhibited significant activity (IC50 13.7 micromol x L(-1)), compared with vitamin C (IC50 59.9 micromol x L(-1)); compounds 1, 3 and 9 showed moderate activity (IC50 161,137, 214 micromol x L(-1)), compared with 2,6-di-tert-butyl-4-methylphenol (IC50 236 micromol x L(-1)); compound 4 and 6 showed weak activity (IC50 264, 299 micromol x L(-1)).

Chemical constituents of leaves of Panax japonicus var. major / 中国中药杂志

Seven compounds were isolated from the leaves of Panax japonicus var. major by chromatographic methods including silica gel, Sephadex LH-20, ODS and semi-preparative HPLC. Their structures were elucidated by their physical and chemical properties and spectral data analysis as 5, 7-dihydroxy-8-methoxyl flavone (1), ginsenoside Rs2 (2), quinquenoside R1 (3), ginsenoside Rs1 (4), notoginsenoside Fe (5), ginsenoside Rd2 (6) and gypenosiden IX (7). Among them, compound 1 was obtained from the Panax genus for the first time, and compounds 2-7 were isolated from this plant for the first time.

Chemical constituents of Jasminum giraldii and their antioxidant activity / 中国中药杂志

Ten compounds were isolated from the barks of Jasminum giraldii by means of various of chromatographic techniques such as silica gel, Sephadex LH-20 and Rp-HPLC. Their structures were identified by spectroscopic data analysis as (+)-medioresinol (1), (+) -syringaresinol (2), syringaresinol-4'-O-beta-D-glucopyranoside (3), oleanic acid (4), 3-methoxy-4-hydroxy-trans-cinnamaldehyde (5), trans-sinapaldehyde (6), syringaldehyde (7), 1-(4-methoxy -phenyl) -ethanol (8), trans-cinnamic acid (9), and 4-(1-methoxyethyl) -phenol (10). Among them, compounds 1-3, 5-8 and 10 were isolated from the J. genus for the first time and compounds 4 and 9 were obtained from J. giraldii for the first time. In the DPPH free radical scavenging assay, compound 1 exhibited significant activity (IC50 55.1 micromol x L(-1)), compared with vitamin C(IC50 59.9 micromol x L(-1)); and compound 2 showed moderate activity (IC50 79.0 micromol x L(-1)), compared with 2, 6-di-tert-butyl4-methylphenol (IC50 236 micromol x L(-1)).

Quantitative Evaluation Method Trillium tschonoskii / 中国药学杂志

OBJECTIVE: To develop a method for the quantitative evaluation Trillium tschonoskii. METHODS: Selecting three penogenin saponins as indicators, a TLC assay was developed for the identification Trillium tschonoskii, and a RP-HPLC assay was established for the content determination. RESULTS: Three penogenin saponins were clearly distinguished by TLC (CHCl3-MeOH-HCOOH-H2O, 6.5:3.5:0.5:1) and well separated by RP-HPLC (CH3CN-H2O, 42:58). The TLC method showed clear spots, and the RP-HPLC method had good linear relationship within the ranges 0.115-0.690 mg · mL-1 for Paris VIII (1) (r=0.9998), 0.135-0.810 mg · mL-1 for penogenin-3β-O-α-L-rhamnopyranosyl-(1→4)-[-O-α-L-rhamnopyranosyl-(1→2)]-O-β-D-gluco-pyraboside(2) (r=0.9996), and 0.225-1.350 mg · mL-1 for Paris VI (3) (r=0.9999). The average recoveries were 99.3%, 98.3%, and 97.7%, respectively. CONCLUSION: The established method is rapid and sensitive for controlling the quality T. tschonoskii.

Dephasing effect on transport of a graphene p-n junction in a quantum Hall regime.

The influence of the dephasing effect on the conductance distribution of disordered graphene p-n junctions is studied. Without the dephasing, the conductance distribution has a very wide range and the conductance fluctuation is large. In this case, the conductance plateaus cannot be obtained in a single sample with the fixed disorder configuration. However, by introducing the dephasing, we find that the distribution becomes narrow dramatically and the fluctuation is suppressed strongly, so that the conductance plateaus are obtained clearly for one single sample, which is consistent with experimental measurements. Furthermore, we also investigate the scaling feature of the conductance distribution and find that it has good scaling behavior in the strong dephasing case.

Electronic transport through a graphene-based ferromagnetic/normal/ferromagnetic junction.

Electronic transport in a graphene-based ferromagnetic/normal/ferromagnetic junction is investigated by means of the Landauer-Büttiker formalism and the nonequilibrium Green function technique. For the zigzag edge case, the results show that the conductance is always larger than e(2)/h for the parallel configuration of lead magnetizations, but for the antiparallel configuration the conductance becomes zero because of the band-selective rule. Therefore, a magnetoresistance (MR) plateau emerges with the value 100% when the Fermi energy is located around the Dirac point. In addition, choosing narrower graphene ribbons can yield wider 100% MR plateaus and the length change of the central graphene region does not affect the 100% MR plateaus. Although the disorder will reduce the MR plateau, the plateau value can still be kept about 50% even in a large disorder strength case. In addition, when the magnetizations of the left and right leads have a relative angle, the conductance changes as a cosine function of the angle. What is more, for the armchair edge case, the MR is usually small. So, it is more favorable to fabricate a graphene-based spin valve device by using a zigzag edge graphene ribbon.