M. Sulaiman

Desmosine, an artefact alkaloid from Desmos dumosus

Abstract The alkaloid, desmosine, an artefact resulting probably from the action of NH 4 OH on a flavone, was isolated from the bark of Desmos dumosus . Its structure was elucidated by 2D NMR experiments.

Li2CO3 – Al2O3 Composite Solid Electrolytes Prepared by Sol Gel Method

Composite solid electrolytes in the system (1-x)Li2CO3-xAl2O3, where x = 0.1–0.7 were prepared by sol gel method using lithium carbonate and aluminum oxide precursors in ethanol. The gels obtained due to the addition of citric acid were calcined at 80 and 100 oC. Their structural, thermodynamic and electrical properties were investigated by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and impedance spectroscopy. The results indicated that interface phases of crystalline and amorphous exist in this composite system of (1-x)Li2CO3-xAl2O3. The presence of the interface phases are due to the chemical and physical interactions between both crystalline Li2CO3 and Al2O3. The Arrhenius plot of the composite system showed non-linear curves and reached maximum values of ∼10−4 - 10−5 S cm-1 at 150 -180 °C. Based on the results of this study, it can be concluded that the sol gel method used in the preparation of the composite system, has an important role to crystal morphology changes that results in high ionic conductivity.

Growth inhibition of foodborne and nosocomial pathogens by aqueous fraction of bearded Argostemma (Argostemma involucratum Hemsl., Rubiaceae).

The crude methanol extract of Bearded Argostemma (Argostemma involucratum Hemsl., Rubiaceae) showed a good and broad spectrum of antibacterial activity against both Gram-negative and Gram-positive bacteria. The activity was increased on fractionation (hexane, dichloromethane and water), particularly in the aqueous fraction which was more active than the methanol extract and streptomycin (no activity was shown against tested moulds). Both the hexane and dichloromethane fractions were inactive. The objective of this experiment was to investigate the antibacterial activity of hexane, dichloromethane, and aqueous fractions of Argostemma involucratum Hemsl. The aqueous fraction of Bearded Argostemma may be a possible new option for the treatment of bacterial infections.

Sol-gel Synthesis and Characterizations of MgSO4- Al2O3 Composite Solid Electrolytes

In this study, composite solid electrolytes in the system (1-x) MgSO4 – x Al2O3 with x = 0.1 0.6 mole were prepared by a citric acid assisted sol-gel method. X-ray diffraction analysis confirmed the transformation of anhydrous MgSO4 to β-MgSO4 upon sintering at 900 ̊C for 2 hours. The prepared composite samples exhibited both crystalline and amorphous state of β-MgSO4. The highest conductivity found was 1.9 ×10 S cm with x = 0.6 at elevated temperatures. The current results show that high concentration of Al2O3 enhanced the disordered phase composite sample thus contributes to high concentration amorphous of composite samples. This has been supported by FTIR, DSC and SEM.