Mohammad S. Mubarak

Electrochemical Reduction of Alkyl Halides at Vitreous Carbon Cathodes in Dimethylformamide

Abstract At vitreous carbon electrodes in dimethylformamide which contains tetramethylammonium perchlorate, cyclic voltammograms for 1-iododecane, 1-bromodecane, and 2-bromooctane consist of one irreversible reduction wave signaling formation of the alkyl carbanion, whereas voltammograms for 2-iodooctane, t-butyl bromide, and t-butyl iodide reveal stepwise generation of the alkyl radical and carbanion. Large-scale electrolysis of 1-iododecane at reticulated vitreous carbon yields decane, eicosane, 1-decene, and 1-decanol; the first two compounds arise, respectively, from reaction of decyl carbanions with a proton donor and with unreduced alkyl iodide, whereas the last two species are produced via chemical attack of hydroxide ion on 1-iododecane. Reduction of 1-bromodecane results in production of decane, 1-decene, and 1-decanol, but little or no eicosane is seen. Electrolysis of 2-bromooctane gives octane, 1-octene, 2-octene, 2-octanol, and 7,8-dimethyltetradecane, the last species probably being formed by coupling of 2-octyl radicals; the other compounds are derived from the 2-octyl carbanion. Although products obtained upon reduction of 2-iodooctane are identical with those from 2-bromooctane, both radicals and carbanions (the relative amounts of which are potential dependent) are involved in the formation of products from the secondary alkyl iodide. A combination of reactions involving t-butyl radicals and t-butyl carbanions is responsible for production of isobutane, isobutylene, and 2,2,3,3-tetramethylbutane during electrolyses of t-butyl bromide.

Protective effects of selenium against cadmium induced hematological disturbances, immunosuppressive, oxidative stress and hepatorenal damage in rats

Cadmium is a non-essential toxic metal used in industrial process, causes severe risk to human health. Selenium (Se) is an essential trace mineral of fundamental importance for human health. Selenium has antioxidant enzymes roles and is needed for the proper function of the immune system. In this study, the protective effects of selenium against cadmium intoxication in rats have been investigated by monitoring some selective cytokines (IL-1β, TNF α, IL-6, IL-10 and IFN-γ), antioxidant enzymes reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and lipid peroxidation malondialdehyde (MDA) as well as some selective biochemical markers of liver and kidney functions. Thirty-two rats were divided into four equal groups; the first group was used as a control. Groups 2-4 were treated with selenium (Se; 0.1mg/kg BW), cadmium (Cd; 40mg/L drinking water) and selenium plus cadmium, respectively. Rats were orally administered their relevant doses daily for 30 days. Blood samples were collected from heart puncture at the end of the experiment (30 days) for complete blood picture (CBC) and serum was separated to evaluate the different immunological parameters and biochemical parameters, as well as liver specimens for Cd and Se estimation. Rats in the Cd treated group have a significantly higher hepatic concentration of Cd than in other treated groups. Results revealed that cadmium significantly increased IL-1β, TNF α, IL-6 and IL-10, beside peripheral neutrophils count, while the IFN-γ and lymphocytes were decreased in rat sera. In addition, GSH level, CAT, SOD and GPx activities were significantly decreased while lipid peroxidation (MDA) was increased. Regarding, liver and renal markers, they were significantly increased in the activities of aminotransferases (AST, ALT), urea and creatinine, while total plasma proteins and albumin were significantly decreased. On the other hand, selenium treated group, showed significantly increased IFN-γ, GSH level, CAT, and GPx activities, as well as lymphocyte count while IL-10 was decreased. Selenium in combination with cadmium, significantly improved the elevation of serum IL-1β, IL-6, TNF α, IL-10 and malondialdehyde in addition to enhancing the antioxidant enzyme activities of GSH, CAT, GPx and SOD. Moreover, selenium has ameliorated the cadmium-induced liver and kidney damage by improving hepatic and renal markers. The results of this investigation demonstrated that selenium has the potential to countermeasure the immunosuppressive as well as hepatic and renal oxidative damage induced by cadmium in rats; selenium has shown promising effects against Cd toxicity.

In-situ electrogeneration of [2,2′-ethylenebis(nitrilomethylidyne)diphenolato]nickelate(I) — nickel(I) salen — as a catalyst for reductive intramolecular cyclizations of 6-iodo- and 6-bromo-1-phenyl-1-hexyne

Abstract In dimethylformamide containing tetraethylammonium perchlorate, the [2,2′-ethylenebis(nitrilomethylidyne)diphenolato]nickel(II) complex, more familiarly known as nickel(II) salen, undergoes reversible one-electron reduction at a carbon cathode to the corresponding nickel(I) species at a potential where 6-iodo- and 6-bromo-1-phenyl-1-hexyne are not electroactive. However, in the presence of the electrogenerated nickel(I) complex, these acetylenic halides are rapidly and catalytically reduced to form a radical intermediate that cyclizes to produce benzylidenecyclopentane in at least 84% yield. This approach to the electrosynthesis of the carbocyclic compound is highly efficient because direct electrolyses of 6-iodo- and 6-bromo-1-phenyl-1-hexyne at carbon cathodes lead to undesired acyclic side-products and to benzylidenecyclopentane in only modest yields.

Synthesis of novel hybrid molecules from precursors with known antiparasitic activity.

Three novel new compounds derived from antiparasitic precursors have been synthesized and tested for their antiamoebic and antigiardial activities. The condensation of 2-(2-methyl-5-1H-nitroimidazolyl)ethylamine (6) with 5-nitro-2-furylacrylic acid (7) gave 3-(5-nitrofuran-2-yl)-N-[2-(5-nitroimidazol-1-yl)ethyl]acrylamide (8). Condensation of 7 with 7-chloro-4-(piperazin-1-yl)quinoline (9) afforded 1-[4-(7-chloroquinolin-4-yl)piperazin-1-yl)-3-(5-nitrofuran-2-yl)propenone as a mixture of two isomers; 10-a (the E-isomer) and 10-b (the Z-isomer). In addition, the reaction of 9 with 1-(2-bromoethyl)-2-methyl-5-nitroimidazole (11) in the presence of K2CO3 and NaI yielded 7-chloro-4-(4-[2-(5-nitroimidazol-1-yl)ethyl]-piprazin-1-yl)quinoline (12). On the basis of preliminary screening data for these new compounds, compound 12 exhibited potent lethal activities against Entamoeba histolytica and Giardia intestinalis; its IC50 ( about 1 µM) was lower, at least by a factor of five, compared to the standard drug, metronidazole. In addition, the IC50 of compound 12 against the tested parasites is 600 times below that against Hep-2 and Vero cells. Compounds 8 and 10-a also exhibited potent or moderate antiamoebic and antigiardial activities with IC50 values of about 5.5 µM, and 140 µM, respectively, against the tested parasites. These two hybrid molecules, 8, 10-a, were also non-cytotoxic at the lethal concentrations against the parasites.

Homogeneous catalytic reduction of α,ω-dihaloalkanes with electrogenerated nickel(I) salen

Abstract Nickel(I) salen, electrogenerated from nickel(II) salen by means of controlled-potential electrolysis at a carbon cathode in dimethylformamide containing tetramethylammonium perchlorate, catalytically reduces α,ω-dihaloalkanes via a one-electron process that yields a radical intermediate. From 1-bromo-4-chloro- and 1-chloro-4-iodobutane, we have obtained 1,8-dichlorooctane as the principal product (> 88%) along with small amounts of 1-chlorobutane (7%–10%) and 4-chloro-1-butene (2%). Catalytic reduction of 1-bromo-5-chloro- and 1-chloro-5-iodopentane affords 1,10-dichlorodecane in high yield (79%–86%) as well as smaller quantities of 1-chloropentane (11%–18%) and 5-chloro-1-pentene (2%–3%). When 1-bromo-6-chloro- and 1-chloro-6-iodohexane are catalytically reduced with nickel(I) salen, 1,12-dichlorododecane is formed in excellent yield (91%–92%), and 1-chlorohexane (9%) and 6-chloro-1-hexene (2%) are minor products.

Catalytic Reduction of 6-Bromo-1-hexene by Nickel(I) Salen Electrogenerated at Glassy Carbon Cathodes in Acetonitrile

Cyclic voltammetry and controlled-potential electrolysis have been used to characterize the catalytic reduction of 6-bromo-1-hexene by nickel(I) salen electrogenerated at a glassy carbon electrode in acetonitrile containing tetramethylammonium tetrafluoroborate. A cyclic voltammogram for the reduction of nickel(II) salen reveals the reversible one-electron process leading to formation of nickel(I) salen, whereas cyclic voltammograms for solutions containing both nickel(II) salen and 6-bromo-1-hexene provide evidence for the catalytic process. Five products (methylcyclopentane, 1-hexene, 1,2-dicyclopentylethane, 7-cyclopentylhept-1-ene, and 1,1 1-dodecadiene) have been separated, identified, and quantitated hy means of gas chromatography and gas chromatography-mass spectrometry.

Electrochemical reduction of di-, tri-, and tetrahalobenzenes at carbon cathodes in dimethylformamide Evidence for a halogen dance during the electrolysis of 1,2,4,5-tetrabromobenzene

Abstract Cyclic voltammetry and controlled-potential electrolysis have been employed to examine the electrochemical reduction of a series of di-, tri-, and tetrahalobenzenes at carbon cathodes in dimethylformamide containing tetramethylammonium perchlorate. Cyclic voltammograms for the reduction of 1,2,4,5-tetrabromo-, 1,2,3,4-tetrachloro-, and 1,2,4,5-tetrachlorobenzene exhibit four irreversible waves, those for 1,2,4-tribromo-, 1,3,5-tribromo-, 1,2,3-trichloro-, 1,2,4-trichloro-, ad 1,3,5-trichlorobenzene show three irreversible waves, and those for 1,3-dibromo-, 1,4-dibromo-, 1,2-dichloro-, 1,3-dichloro-, and 1,4-dichlorobenzene reveal two irreversible waves. Products derived from the electrolytic reduction of 1,2,4,5-tetrabromobenzene are 1,2,4-tribromo-, 1,3-dibromo-, and 1,4-dibromobenzene, along with 1,3,5-tribromobenzene, and the appearance of the last compound indicates that an electrolytically induced halogen dance takes place. For all of the other polyhalobenzenes investigated, except 1,2-dibromobenzene, the distributions of electrolysis products are consistent with expectations based on their voltammetric behavior.

Alkyl Group Incorporation into Nickel Salen during Controlled-Potential Electrolyses in the Presence of Alkyl Halides

During the catalytic reductions of 1-iodooctane, 1-bromooctane, and 1-iodobutane by nickel(I) salen, electrogenerated from nickel(II) salen at a carbon cathode in dimethylformamide containing 0.10 M tetraethylammonium tetrafluoroborate, less than 100% of the alkyl halide is converted into hydrocarbon products (although virtually none of the original alkyl halide remains) and the transition-metal complex loses its activity. For a system originally consisting of nickel(II) salen and either 1-iodooctane or 1-bromooctane, analyses of post-electrolysis solutions by means of high-performance liquid chromatography reveal that the original nickel(II) salen is largely transformed into three new species. Electrospray-ionization mass spectrometry indicates that one species is a monooctylated nickel(II) salen and another species is a dioctylated nickel(II) salen. Nuclear magnetic resonance spectrometry [i.e., correlated spectroscopy (COSY), nuclear Overhauser effect spectroscopy (NOESY), and total correlated spectroscopy (TOCSY) techniques] has been utilized to establish the sites of octylation. For the l-iodobutane-nickel(II) salen system, at least three butylated nickel(II) salen species have been detected, among which are monobutylated and dibutylated complexes.

Copper Adsorption on Chitosan-Derived Schiff Bases

The adsorption of Cu(II) ions onto the chitosan derived Schiff bases obtained from the condensation of chitosan with salicyaldehyde (polymer I), 2,4-dihydroxybenzaldehyde (polymer II) and with 4-(diethylamino) salicyaldehyde (polymer III) in aqueous solutions was investigated. Batch adsorption experiments were carried out as a function of contact time, pH, and polymer mass. The amount of metal-ion uptake of the polymers was determined by using atomic absorption spectrometry (AAS) and the highest Cu(II) ions uptake was achieved at pH 7.0 and by using sodium perchlorate as an ionic strength adjuster for polymers I, II, and III. The isothermal behavior and the kinetics of adsorption of Cu(II) ions on these polymers with respect to the initial mass of the polymer and temperature were also investigated; adsorption isothermal equilibrium data could be clearly explained by the Langmuir equation. The experimental data of the adsorption equilibrium from Cu(II) solution correlates well with the Langmuir isotherm equation.

Quantitative ethnobotanical survey of medicinal flora thriving in Malakand Pass Hills, Khyber Pakhtunkhwa, Pakistan

STUDY OBJECTIVE Ethnobotanical knowledge is proving to be invaluable for drug discovery in the wake of effective prospecting from biodiversity. On the other hand, the escalating human pressure is threatening the endogenous flora. Situated at the foothill of the Himalayas, Pakistan boasts of rich floristic distribution. However, many lush yet imperiled regions of this country has never been explored. It inspired us to evaluate and document the taxonomic composition, significance of medicinal plants and associated traditional knowledge in the District of Malakand, Khyber Pakhtunkhwa Province. MATERIALS AND METHODS Vegetation growing in Malakand pass hills, Pakistan was studied and data were collected using an open-ended questionnaire, in addition to interviewing the local elderly, knowledgeable persons, and herbal practitioners. Relative Frequency Citation (RFC) and Use Value (UV) of the medicinal plants were calculated and their correlation was determined by Pearson correlation coefficient. RESULTS This study encompasses 92 plant species belonging to 56 families thriving in the study area. The information gathered includes ethnobotanical inventory and their pharmacological uses. Quantitative analysis throws light on the consistence of RFC and UV. Asteraceae and Lamiaceae were the most abundant families represented by 6 species each. Shoots were the most used parts (23.6%) and wound healing (7.91%) was the most common therapeutic use. CONCLUSION The result obtained from the study implies that local inhabitants rely on these plants for their medicinal requirements. Also, the statistics reveal that, the vegetation can be assessed for potential drug leads. However, urban expansion is threatening the existence of indigenous flora and old generation with ancient herbal wisdom is perishing. So, it appears imperative to preserve the traditional knowledge. This survey is expected to contribute to the discovery of novel bioactive constituents, stimulate conservation efforts of the perturbed flora and promote sustainable exploitation of the medicinal bounty.