Nguyen Thi Mai

Two new C-Glucosyl benzoic acids and flavonoids from mallotus nanus and their antioxidant activity

Two new 2-C-β-D-glucopyranosyl benzoic acid derivatives named mallonanosides A (1) and B (2) were isolated from the methanolic extract of the leaves of Mallotus nanus along with five known flavonoids, kaempferin (3), juglanin (4), quercitrin (5), myricitrin (6), and rhoifolin (7). Their structures were established on the basis of spectral and chemical evidence. Their antioxidant activities were shown to depend on the number of hydroxyl groups, and the location and species of sugar moiety.

Magnetic memory effect in a strong phase competition system La0.7Ca0.3Mn0.925Ti0.075O3

A magnetic memory effect was observed by means of zero-field-cooled magnetization measurements in a temperature range below TC. The magnitude of magnetic memory effect, determined by the difference between the magnetization curve with a pause of temperature during the cooling process and its reference curve without the pause, showed that it is independent of the number of pauses. The memory effect is supposed to be related to the isolated states with an infinite degeneration, which is associated with the presence of magnetic frustration in a system with a strong magnetic phase competition. Besides, a resistance memory effect was concomitantly observed at the same pause temperatures.

Steroidal saponins from Datura metel

&NA; Datura metel L. (Solanaceae) is an annual herb that has been widely used in the traditional medicine for the treatment of coughs, bronchial asthma, and rheumatism. Chemical investigation of an acidic methanol extract of the whole plants of D. metel resulted in the isolation of five new steroidal saponins (1–3, 5, and 6), named metelosides A‐E, and four known compounds (4, 7–9). Their structures were elucidated by extensive spectroscopic methods, including 1D and 2D NMR and MS spectra. The structures of metelosides A and B were found to be unusual among the reported spirostane‐type steroidal saponins due to the presence of the acetamide groups in the molecules. Compounds 2, 4, 5, and 6 were shown to be cytotoxic against three cancer cell lines, including HepG2, MCF‐7, and SK‐Mel‐2 cells. Furthermore, compounds 3, 4, and 7 exhibited modest anti‐inflammatory effects through inhibition of NO production in LPS‐stimulated BV cells. Graphical abstract Figure. No caption available. HighlightsNine compounds were isolated from Datura metel.The structures of five new steroidal saponins and 4 known compounds were identified by spectroscopic methods.Four compounds were cytotoxic against HepG2, MCF‐7, and SK‐Mel‐2 cells.Three compounds inhibited NO production in LPS‐stimulated BV cells.

Bisbenzylisoquinoline alkaloids from Mahonia nepalensis

From the wood of Mahonia nepalensis DC. 1821 , two bisbenzylisoquinolines homoaromoline ( 1 ) and isotetrandrine ( 2 ) were isolated by using various chromatoghraphies. Their structures were characterized on the basis of the spectroscopic data (1D-NMR, HSQC, HMBC, ESI-MS) in comparison with the literature. This is the first report of 1 - 2 from Mahonia nepalensis. Keywords: Mahonia nepalensis, Isotetrandrine, Homoaromoline, B isbenzylisoquinoline.

Stability and magnetic properties of isomorphous substituted Si7-xMnx+

The optimized geometries, stability, and magnetic properties of cationic clusters Si 7 + , Si 6 Mn + , and Si 5 Mn 2 + have been determined by the method of density functional theory using the B3P86/6-311+G(d) functional/basis set. Their electronic configurations have been analyzed to understand the influence of substituting Si atoms by Mn atoms on the structural and magnetic aspects of Si 7 + . It is shown that the manganese dopant does not alter the structure of the silicon host but significantly changes its stability and magnetism. In particular, while the magnetic moment of Si 7 + is 1 m B , Si 5 Mn 2 + exhibits a strong magnetic moment of 9 m B and that of Si 6 Mn + takes a relatively high value of 4 m B . Among studied clusters, the pentagonal bipyramid Si 5 Mn 2 + is assigned as the most stable one.

Chemical constituents of Datura metel L.

Chemical investigation of an acidic methanol extract of the whole plant of Datura metel resulted in the isolation of seven compounds, including pterodontriol B ( 1 ), disciferitriol ( 2 ), scopolamine ( 3 ), adenosine ( 4 ), thymidine ( 5 ), ilekudinoside C ( 6 ), and dioscoroside D ( 7 ). Their structures were elucidated by extensive spectroscopic methods, including 1D and 2D NMR and mass spectra and in comparison with reported data in the literature. Among the isolated compounds, pterodontriol B, disciferitriol, ilekudinoside C, and dioscoroside D were reported for the first time from the Datura genus. Keywords. Datura metel, Solanaceae , sesquiterpene, triterpenoid saponin, steroidal saponin.

Petrography and geochemistry of Permian basalts of the Cam Thuy formation and their relation to Song Da and Emeishan magmatic rocks

Cam Thuy Permian basalts consisting of thick lava flows and pyroclastic layers appear along both sides of the Song Ma fault zone in Thanh Hoa and in Son La and Ninh Binh provinces, NW Vietnam. The magmatism has been thought to have genetic relationship with Permian volcanism in the Song Da rift zone, which is believed to be part of the Emeishan large igneous province, having been extruded along the Red River shear zone following Paleogene India-Eurasian collision. A set of Cam Thuy volcanic samples including olivine and alkaline basalts was collected in the Lam Son area (Tho Xuan, Thanh Hoa province) to analyze for geochemical major, trace element and Sr-Nd-Pb isotopic composition. The Cam Thuy basalts are high-TiO2, CaO, FeO*, moderate MgO and SiO2 that plot between the Song Da and Emeishan highand low-Ti basalt distribution fields and closely overlap that of Song Da’s high-Ti field. The primitive mantle and chondrite normalized trace element patterns of Cam Thuy basalts are essentially enriched oceanic island basalt (OIB)-like; this feature, together with crustal contamination-free, chondritic Sr, Nd and Pb initial (255Ma) isotopic composition are certainly of asthenospheric origin. These geochemical and isotopic characteristics are closely analogous to those features observed for the Song Da high-Ti basalts, suggesting similarity in their source of origin. Nevertheless, while the Song Da (and Emeishan) magmatism is signified by the presence of both highand low-Ti basalts, with the latter being derived from heterogeneous and partially crustal-material contaminated sources in the lithospheric mantle, this low-Ti volcanic rock type has yet to be discovered in the Cam Thuy formation.