Hamza Abba

MNDO and DFT Computational Study on the Mechanism of the Oxidation of 1,2-Diphenylhydrazine by Iodine

The reaction mechanisms of the oxidation of 1,2-diphenylhydrazine by iodine have been examined using semiempirical and density functional theory methods, the oxidation proceeded via two independent pathways that can be separately monitored. One pathway involved the chain multistep mechanism. The other pathway occurred via a one-step mechanism in which a “cyclic” activated complex was formed which on disproportionation gave the products. The one-step “cyclic” activated complex mechanism proceeds more rapidly than the chain multistep mechanism. The results were explained by analyses based on computational energetics of the optimised reactants, intermediates, transition states, and products of the reaction of iodine with 1,2-diphenylhydrazine.

Effect of Acetylation on Stability to Retrogradation of Starch Extracted from Wild Polynesian Arrowroot (Tacca leontopetaloides (L.) Kuntze) for Utilization as Adhesive on Paper

Starch was isolated from T. leontopetaloides tubers, chemically modified by acetylation with varying amounts of acetic anhydride. Monolayer of the ten acetylated and control starch powders was exposed on roof top for five weeks and pastes of both exposed and unexposed (control) samples were prepared with distilled water (1 : 3 w/w). The effects of acetylation, degree of substitution (DS), and exposure to sunlight were investigated to evaluate the retrogradation tendency of the adhesive pastes from changes in syneresis, tack strength, optical clarity, viscosity, gelation time, and drying time. The results obtained showed that all the adhesive properties studied were affected by both DS and exposure to sunlight. While tack strength, viscosity, and drying time were found to increase with increase in DS, syneresis, optical clarity, and gelation time were found to decrease with increase in DS. Increase in tack strength and reduction in syneresis imply that the acetylation treatment has made T. leontopetaloides starch more suitable for use in remoistenable adhesive applications. The reduction in syneresis, optical clarity, and gelation time with increase in DS was attributed to the strengthening of the bonds between the amylose and amylopectin molecules, preventing water leaching out of the starch granules.

The Use of Glutamic Acid as Corrosion Inhibitor for Aluminium in Hcl Solution

The adsorptive and inhibitive action of glutamic acid towards general and pitting corrosion of aluminium in HCl solution was investigated using weight loss, gasometric and thermometric methods. Glutamic acid was found to inhibit the corrosion of aluminium in HCl solution. The inhibition efficiency of glutamic acid decreased with increase in temperature, period of immersion and HCl concentration, but increased with increasing glutamic acid concentration. Adsorption characteristics of glutamic acid have also been studied and it was found that the process obeys physical adsorption. Thermodynamic parameters including; Ea, Qads, ∆Sads, ∆Hads and ∆Gads for the adsorption process signifies a spontaneous process. While Langmuir, Frumkin, Flory- Huggins and El-Awardy isotherm adsorption models can be used to explain the mechanism of glutamic acid adsorption onto aluminium surface in HCl solution.

In-vitro Evaluation of Aqueous Extracts of Citurs sinensis, Aloe vera and Their 1:1 Extracts Blend on Protein Denaturation during Acute Inflammation

Abstract Citrus sinensisand Aloe veraare well known and widely used herbs, which contains several interesting bioactive constituents and possesses health promoting properties. Oxidative stress contributes to the pathogenesis and progression of many diseases. The use of natural antioxidant, as a therapeutic option, is desirable and increasingly being practised. The aim of the present study is to evaluate and compare the antiinflammatory effects of aqueous extracts of Citrus sinensisand Aloe veraand a 1:1 blend of the two extracts against the denaturation of protein in vitro. The test extracts of varying concentrations were incubated with egg albumin under controlled experimental conditions and subjected to determination of absorbance to assess the anti-inflammatory property. A standard anti-inflammatory drug, Ibuprofen, was used as reference drug. The results obtained exhibited a concentration- dependent inhibition of protein (albumin) denaturation by both extracts, including the 1:1 blend of the extracts. From the present findings, it can be concluded that both Citrus sinensisand Aloe verapossessed a marked anti-inflammatory effect against the denaturation of protein, in vitro. Aloe verawas found to be slightly more active than Citrus sinensis, possibly due to the higher flavonoids contents of Aloe vera.