Intrinsically low thermal conductivity of bismuth oxychalcogenides originating from interlayer coupling.

The anharmonicity of phonons in a solid is ultimately rooted in the chemical bonding. However, the direct connection between phonon anharmoncity and chemical bonding is difficult to make experimentally or theoretically, mainly due to their complicated lattice structures. Here, with the help of first-principles calculations, we show that the intrinsically low lattice thermal conductivity (κ) of Bi2O2X (X = S, Se, Te) shows a strong connection to the electrostatic inter-layer coupling. We explain our results by the strong anharmonic chemical bonding between Bi and chalcogen atoms. Additionally, due to the strong anharmonicity, a large portion of phonon modes has a mean free path shorter than the average atomic distance. We employ a recently proposed two-channel model to take into account their contribution to κ.

[Comparative study on antibacterial effects of huangqin-tang and its metabolites produced by intestinal flora].

OBJECTIVE: To compare the antibacterial effects of Huangqin-Tang with its metabolites produced by intestinal flora. METHOD: The antibacterial tests in vitro and in vivo were performed by agar dilution method and lethal protection of animal respectively. RESULT: Huangqin-Tang and its metabolites had antibacterial action on bacteria in vitro, however the antibacterial activity of metabolites of Huangqin-Tang on Salmomella, Dysentery bacillus and Proteus in vitro was stronger than Huangqin-Tang. The metabolites of Huangqin-Tang had protective effect on the animals infected by Staphylococcus aureus and Escherichia coli respectively from death, but Huangqin-Tang had no lethal protection action. CONCLUSION: The antibacterial effects of metabolites of Huangqin-Tang in vitro and in vivo are stronger than that of Huangqin-Tang, which shows that intestinal flora play a very important role in antibacterial effects of Huangqin-Tang.

[A comparison of the protective activity of liver injury induced by D-galact-osamine between huangqin-tang and their metabolites by human intestinal bacteria].

OBJECTIVE: To compare the protective activity of liver injury induced by D-galactosamine (GalN) between Huangqin-Tang and their metabolites by human intestinal bacteria(HIB). METHOD: The liver injuries in conventional and pseudo-germfree mice were induced by GalN. After oral administration of Huangqin-Tang and their metabolites mixtures by HIB, the serum transaminase (ALT and AST) activities were detected. RESULT: In conventional mice, large and medium doses (20 and 10 g.kg-1) of Huangqin-Tang decoction significantly reduced the increase of serum ALT activity after 18 h GalN treatment. In pseudo-germfree mice, metabolites significantly reduced the ALT levels. However, Huangqing-Tang didn't affect the ALT levels in this kind of mice. To all of the animals, AST levels remained the same after oral Huangqin-tang or their metabolites. CONCLUSION: The metabolism by intestinal bacteria plays a role in pharmacological effects of constituents of Chinese herbal medicine. The metabolites of the constituents by intestinal bacteria were the real active components in vivo.

Metabolism of constituents in Huangqin-Tang, a prescription in traditional Chinese medicine, by human intestinal flora.

In the course of studies on the metabolism of active components of Huangqin-Tang by human intestinal flora (HIF), Huangqin-Tang and all individual herbs in the decoctions were incubated with a human fecal suspension separately. By using a high-performance liquid chromatographic (HPLC) method which was previously established in our laboratory, the metabolites in both the compound prescription and all the single herb decoctions were identified and determined both qualitatively and quantitatively. We found that the constituents of Huangqin-Tang, incluing baicalin (baicalein 7-glucuronide; BG), wogonoside (wogoninoglucuronide; WG), oroxylin-A-glucuronide (OG) from Scutellariae Radix, paeoniflorin (PF) from Paeoniae Radix, liquiritin (liquiritigenin 4'-O-glucoside; LG), isoliquirtin (isoliquiritigenin 4-glucoside; ILG) and glycyrrhizic acid (GL) from Glycyhhizea Radix, were converted to their metabolites baicalein (B), wogonin (W), oroxylin-A (O), paeonimetabolin-I (PM-I), liquiritigenin (L), isoliquiritigenin (IL) and glycyrrhetinic acid (GA) by HIF. The contents of the metabolites in Huangqin-Tang and in each single herb decoction increased significantly after incubation with intestinal flora. Comparing with single herb decoctions, the transformation of BG, WG, OG, LG and ILG in the compound prescription was promoted, however, that of PF and GL was inhibited. All the results suggested that the glycosides of many medicinal herbs could be converted to aglycones by HIF, and the metabolism of most glycosides was improved in the compound prescription.