Zanariah Abdullah

On-line preconcentration and determination of trace metals using a flow injection system coupled to ion chromatography

A flow injection (FI) method with on-line preconcentration using a mini-column loaded with 8-hydroxyquinoline immobilized on controlled pore glass (CPG-8HQ) is described for the determination of trace metals by ion chromatography (IC) with pyridine-2-6-dicarboxylic acid (PDCA) as the eluent. Copper, cadmium, lead, zinc, nickel and iron were determined at ppb level after post-column derivatization with 4-(2-pyridylazo)-resorcinol (PAR). The detection limits (3sigma) for the FI/IC system were 8.27, 0.89, 0.09, 0.06, 0.09 and 0.07 g l(-1) for Pb(2+), Cd(2+), Cu(2+) Ni(2+), Zn(2+) and Fe(3+), respectively, using 5 ml sample volume. The method was applied to the analysis of Malaysian natural waters.

Synthesis and Antibacterial Evaluation of Some Novel Imidazole and Benzimidazole Sulfonamides

Several new substituted sulfonamide compounds were synthesized and their structures were confirmed by 1H-NMR, 13C-NMR, FT-IR, and mass spectroscopy. The antibacterial activities of the synthesized compounds were screened against standard strains of six Gram positive and four Gram negative bacteria using the microbroth dilution assay. Most of the compounds studied showed promising activities against both types of bacteria.

Strychnan and secoangustilobine A type alkaloids from Alstonia spatulata. Revision of the C-20 configuration of scholaricine.

A total of 25 alkaloids were isolated from the leaf and stem-bark extracts of Alstonia spatulata, of which five are new alkaloids of the strychnan type (alstolucines A-E, 1-5) and the other, a new alkaloid of the secoangustilobine A type (alstolobine A, 6). The structures of these alkaloids were established using NMR and MS analysis and, in the case of alstolucine B (2), also confirmed by X-ray diffraction analysis. A reinvestigation of the stereochemical assignment of scholaricine (13) by NMR and X-ray analyses indicated that the configuration at C-20 required revision. Alkaloids 1, 2, 6, 7, 9, 10, and 13 reversed multidrug resistance in vincristine-resistant KB cells.

Seco-tabersonine alkaloids from Tabernaemontana corymbosa

Two seco-tabersonine alkaloids, jerantiphyllines A and B, in addition to a tabersonine hydroxyindolenine, jerantinine H, and a recently reported vincamine alkaloid 7, were isolated from the leaf extract of the Malayan Tabernaemontana corymbosa and the structures were established using NMR and MS analysis. Biomimetic conversion of jerantinines A and E to their respective vincamine and 16-epivincamine derivatives were also carried out.

Tetrakis-imidazolium and benzimidazolium ionic liquids: a new class of biodegradable surfactants

Novel series of tetra-cationic ionic liquids containing alkyl or phenyl side chains and ester groups within the same molecule were successfully prepared. Based on imidazolium and benzimidazolium, these ionic liquids were synthesized from readily available starting materials in high yield. Surfactant properties including liquid crystalline behaviour and surface properties as well as their biodegradability were investigated. Tetrakis-imidazolium ionic liquid compounds showed assembly behaviour in the pure form (i.e. spontaneously) and in the presence of polar or nonpolar solvents, while both imidazolium and benzimidazolium ionic liquids effectively reduced the surface tension of water in the range of 29–34 mN m−1. The incorporation of tetra alkyl or phenyl side chains into imidazolium and benzimidazolium ionic liquids with tetra-ester groups, significantly improved the biodegradation. ‘Closed-Bottle Test’ OECD 301D and sodium n-dodecyl sulphate (SDS) as a reference were used for evaluation. The linear alkyl side chains (i.e. butyl, hexyl, octyl, decyl and dodecyl) in both tetrakis-imidazolium and benzimidazolium ionic liquids promote the increasing in biodegradation and phase behaviour results comparing to aromatic side-chains.

2-(3-Meth­oxy­phen­oxy)pyrimidine

In the title compound, C11H10N2O2, the benzene ring faces towards one of the pyrimidine N atoms, and is almost orthogonal to the plane through the pyrimidine ring [dihedral angle = 84.40 (14)°]. In the crystal, the presence of C—H⋯π and π–π [centroid–centroid separation = 3.7658 (18) Å] interactions leads to a supramolecular array in the ac plane. The layers thus formed interdigitate along the b axis.

Bis-imidazolium and benzimidazolium based gemini-type ionic liquids structure: synthesis and antibacterial evaluation

Based on bis-imidazolium and benzimidazolium, new sets of geminal dicationic ionic liquids containing a sulphonamide moiety were successfully synthesized with good yields. Their structures were confirmed by 1H-NMR, 13C-NMR, FT-IR, and mass spectroscopy. Selected physicochemical properties of these ILs including thermal stability by TGA and miscibility in some common organic solvents and water were also determined. Most of the prepared dicationic ILs displayed significant levels of antibacterial activities against ten selected bacterial strains of Gram-positive and Gram-negative using a micro-broth dilution assay.

New thiosemicarbazides and 1,2,4-triazolethiones derived from 2-(ethylsulfanyl) benzohydrazide as potent antioxidants.

New thiosemicarbazide derivatives 2-6 were synthesised by reacting 2-(ethylsulfanyl)benzohydrazide with various aryl isothiocyanates. The cyclisation of compounds 2-6 under reflux conditions in a basic medium (aqueous NaOH, 4 N) yielded compounds 7-11 that contain a 1,2,4-triazole ring. All of the synthesised compounds were screened for their antioxidant activities. Compounds 2, 3, and 7 showed better radical scavenging in a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, with IC50 values of 1.08, 0.22, and 0.74 µg/mL, respectively, compared to gallic acid (IC50, 1.2 µg/mL). Compound 3 also showed superior results in a ferric reducing antioxidant power (FRAP) assay (3054 µM/100 g) compared to those of ascorbic acid (1207 µM/100 g).

Lumusidines A-D and villalstonidine F, macroline-macroline and macroline-pleiocarpamine bisindole alkaloids from Alstonia macrophylla.

Lumusidines A-D, bisindole alkaloids of the macroline-macroline type, and one of the macroline-pleiocarpamine type, villalstonidine F, were isolated from the stem-bark extract of Alstonia macrophylla (Apocynaceae). The structures and absolute configurations of these alkaloids were established using NMR, MS, and X-ray diffraction analyses.

N-(4-Methyl­phen­yl)-3-nitro­pyridin-2-amine

Two independent molecules comprise the asymmetric unit of the title compound, C12H11N3O2. These differ in terms of the relative orientations of the benzene rings as seen in the respective dihedral angles formed between the pyridine and benzene rings [17.42 (16) and 34.64 (16)°]. Both molecules are twisted about the amine–tolyl N—C bonds [respective torsion angles = 22.3 (5) and 35.9 (5)°] but only about the amine–pyridine N—C bond in the first independent molecule [respective torsion angles = −11.7 (5) and 0.8 (5)°]. Intramolecular N—H⋯O hydrogen bonds preclude the amine H atoms from forming significant intermolecular interactions. The crystal packing features intermolecular C—H⋯O and C—H⋯π and π–π [centroid–centroid distance: pyridine–benzene = 3.6442 (19) Å and pyridine–pyridine = 3.722 (2) Å] contacts.