Department of Chemistry

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Department of Chemistry

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Open Access
Chemistry in the Economic Development of Nigeria
(Obafemi Awolowo University Press, 1979-10-18) Oke, O. L.
It is possible to ascertain how much curiosity oriented research has contributed to the economic development of an industrialised country by identifying key discoveries with profitable applications and estimating the economic benefit if it was discovered later. We in the developing countries feel that science (especially chemistry) has contributed greatly to the economic development of the industrialised countries and so we assume that expansion of scientific research and teaching (as is done in these: countries) will automatically lead to wealth. We have failed to realise that the majority of these basic sciences derive most of their impetus and motivation from technologies, and also these industrialised countries with only 25% of the world's population have between 80-90% of the world's research power. If we therefore teach the basic sciences the way it is done in these countries without modification, and conduct similar research, it means our products will be more suitable for these countries than ours.
Open Access
Kinetics and Mechanism of Aquation of Tris (3, 4, 7, 8 - Tetramethyl - 1, 10 - Phenanthroline) Iron (II) Suphate in Aqueous Sodium Lauryl Sulphate.
(Obafemi Awolowo University, 1984) Soriyan, Oladega Omopariola; Ige, Jide
In this thesis we report the kinetics and mechanism of the aquation of tris(3, 4, 7, 8-tetramethyl1,10 phenanthroline) Iron(II) sulphate in aqueous micellar solution of Sodium Lauryl sulphate(NaLS). The aquation is inhibited by NaLS in the presence of H+, OH- , SO42- , NH4+ and tetraethylammonium ion (Et4N*). The inhibition is attributed to the stable association or binding between the complex and the micelle and the decrease in the activity of water in the micellar phase. The partitioning of the substrate between the bulk water solution and the micellar phase is in favour of the latter. The kψ-[surfactant] profiles are structured due to micellar evolution. A mechanism which fits kinetic data at low surfactant concentration is proposed. From the rate law obtained and kinetic data observed, the micelle-complex binding constant K1 and micelle-acid binding constant K3 are calculated to be 2.81 x 105 and 13.80 mol -1dm3 respectively in acid medium. Using Scat chard method, K1 in neutral medium is 3.95 x 105 mol-ldm3. The decrease in K1 in acid medium is due to competition for the binding sites on the micelle by the acid proton H+ and the complex ion. The rate of reaction is a function of equilibrium distribution of all the substrates between the micellar phase and bulk water phase. The evolution of the micelle with respect to the c.m.c. is also a function of the nature of the substrate present in solution. Calculated activation parameters suggest strong steric stabilisation of the transition state with respect to enthropy. The magnitudes of activation parameters ΔH# and ΔS# are functions of the surfactant concentration. ΔH# (KJ mol-1) and ΔS# (JK-1 mol-1) for the aquation in 0.00, 1.0 x 10-4 and 2.0 x 10-4 mol dm-3 NaLS are respectively: 100.40 ± 2.04, 22.58 ± 0.16; 111.48 ± 1.15, 48.94 ± 0.09; 119.19 ± 1.15, 67.16 ± 0.09 in 1.00M H2SO4.
Open Access
Chemical Examination of the Leaves of AZADIRACHTA INDICA A. JUSS. (NEEM) for Insect Anti-Feedants.
(Obafemi Awolowo University, 1985) Adesanya, Adepeju Olubamwo; Ogunkoya, L.
The chemistry of the extractives from the leaves of Azadirachta indica and its closely related species, Melia azedarach is reviewed. Cold methylated spirit was resolved into four fractions on the basis of their solubilities in the non-polar solvent hexane and in aqueous alkali. Each of these fractions was tested for repellent activity on the bean seed weevil; Callosobruchus maculatus. three of the fractions inhibited the emergence of the bean seed weevils and were therefore considered to possess the expected insect repellent activity. From one of these fractions, thick oil was isolated after purification using idolumn and thin layer chromatographic methods. Spectroscopic studies of this thick oil revealed the presence of one major compound whose molecule contained an ester group and a C=C in conjugation with another Pi electron system.
Open Access
Chemical Studies on Human Breast Milk.
(Obafemi Awolowo University, 1985) Jeje, Temitayo Enitan; Oke, O. L.
The variation in some chemical constituents of human breast milk from the first month to the fifteenth month of' breast-feeding was studied. Deductions were then made as to the effect this variation had on the nutritional status of the children whose mothers' breast milk was collected. This study was done on milk samples collected from nursing mothers of children who were healthy and of those who were malnourished. The results obtained showed a decrease in the protein and immunoglobulin contents for both groups studied. An increase in the lactose content was observed for the healthy group while no definite trend could be discerned in the malnourished group. The average values obtained for proximate compositions were: Protein: 1.30+0.18g/100ml; 1.27+0.30g/100ml; Fat: 1.85+1.06%; 1.39+37%; Lactose: 5.77+2,5g/100ml; 7.19+1.73g/100ml; pH: 7.03+0.22; 6.54+0.30: For the healthy and malnourished groups respectively. Values obtained for immunoglobulin were: IgA 117.00g/100ml to 100.00g/100ml and 25.00g/100ml to 6.00g/100ml; IgG 27.00g/ 100m1 to 16.00g/100ml and 12.00g/100ml to 8.00g/100ml, for the healthy and malnourished groups respectively. The thiocynate content of the analysed milk varied from a minimum of 0.35, u mole/1 to a maximum of 0.90, u mole/1, for the healthy group and for the malnourished group from a minimum of 0.10, u mole/1 to a maximum, 0.75 p mole/1. Amino acid values for the malnourished group were slightly higher than those for the Healthy group with the exception of lysine. The limiting amino acid in both groups was methionine. The children in this study were observed to grow well during the first four months of life until retardation in growth started reaching a maximum at the sixth month. This period was observed to correspond with the weaning period, when maize gruel (ogi) or Baby Custard diet had been introduced. The extent and duration of these food supplements presumably tend to influence to a large extent the eventual nutritional status of the infant.
Open Access
The Metabolism of Dhurrin in Sorghum Seedlings 1: Distribution, Biosynthetic Site and Function
(Faculty of Agriculture, University of Ife, 1985) Adewusi, S. R. A.
The variation of dhurrin in various parts of sorghum seedlings was monitored over a period of 28 days. The results showed that a peak of 2.8 urn01 was reached in the shoot on the 8th day while in the root, it was only 0.24 umol on the 7th day. Dhurrin concentration reduced with age and size of seedlings. Labelling studies with 14C-shikimic acid showed that all the tissues synthesized and stored dhurrin; above 90% of the radioactivity was found in the dhurrin of the root. Different parts of sorghum seedlings showed ability to synthesize dhurrin from 14C-tvrosine. In vitro synthesis of dhurrin by microsomal fractions of the different parts also confirmed this. Analysis of the dhurrin content of the first, second and third leaves showed a fair distribution in the first leaf, The second and third leaves however showed a gradient from the apex to the stalk. The results are discussed on the basis of dhurrin distribution, biosynthetic capability of the parts and function.
Open Access
Comparative Analytical Methods for the Monitoring of Polyaromatic Hydrocarbons in Nigerian Crude Oil.
(Obafemi Awolowo University, 1985) Fakankun, Olusola Akanbi; Adeyemi, S. A.
This study involves the use of comparative analytical techniques for the monitoring, determination and characterization of poly-aromatic hydrocarbon compounds found in Nigerian crude oils collected from Bonny, Brass, Escravos, Forcados, Pennington and Qua-Iboe Terminals. The analytical approach adopted involved the use of conventional fluorimetry, synchronous excitation, nuclear magnetic resonance, high performance liquid chromatography coupled to ultraviolet and fluorescence detectors, and gas chromatograph - mass spectrometry techniques. Certain physicochemical measurements of the crude oils such as viscosity, elemental analysis, specific gravity and refractive index were also measured. All the crude oil samples from the seven terminals were found to contain about the same number of isomeric polynuclear hydrocarbons, for instance, the major isomeric compounds found in most of the crude oils analysed were carbazole, benzofluorene, naphthalenes, phenanthrenes, anthracenes, benzo(a, b, c)pyrenes, C1- C3 akylbencenes, and C1 - C4 alkylnaphthalenes. From the results obtained an average of forty polynuclear aromatic hydrocarbons could be classified as priority pollutants in the Nigerian crude oil. Among the techniques used, HPLC-UV happens to be the most suitable technique in that many more compounds were identified relative to other techniques such as GC - MS, fluorescence, However, the GC - MS result obtained from Ebubu flow station sample was used as a confirmatory guide to the comparative analytical techniques employed in this study.
Open Access
Periodate Oxidation of Tris-(4,4'- Dimethyl-2.2' Bipyridine) iron (ii)
(Obafemi Awolowo University, 1986) Ayodele, Ezekiel Temitayo
This work covers the periodate oxidation of tris-(4,4'-dimethyl-2,2'-bipyridine) iron (II) complex. The reactive periodate species postulated from the ionic strength dependence in acid medium are IO3+ H6IO6 or I(OH)6+. In both acid and neutral med the ionic strength dependence of observed rate constant was found to fit into Bronsted Bjerrum Christiansen formulation while in alkaline medium significant deviation was observed. In acid medium, a reaction order of 0.2 obtained with respect to the periodate ion species shows that the reaction proceeds via a complex mechanism. The reaction was found to be acid dependent, and protonation of the periodate or complex occurs prior to electron transfer and the reaction proceeds by outer-sphere mechanism. In alkaline medium, the formation of mesoperiodate and other polymeric species for which the accompanying equilibria are not precisely known makes the reaction more complex and the postulation of a reasonable mechanism impossible. In neutral medium as in acid medium, reaction proceeds through the formation of an outer-sphere complex. At low periodate ion concentration, a stoichiometry of 1:1 with respect to the complex and periodate was obtained while at high periodate ion concentration the stoichiometry is 3:1.
Open Access
Preparation and Conductivity Measurements of some Metal 9, 10- Dihydroxyoctadecanoates
(Obafemi Awolowo University, 1986) Mbaneme, Prince Chukwulozie; Akanni, M.S.
The preparation of 9,10-dihydroxyoctadecanoic acid is carried out using oleic and elaidic acids as reported by Swern and Co-workers. Characterization of the acids is done by taking the melting points and the infrared spectra. The 9,10-dihydroxyoctadecanoic acid obtained from Oleic acid is used in preparing lead(II), Zinc(II), Mercury(II) and Cadmium(II) 9,10-dihydroxyoctadecanoates. The identity of lead(II) and Zinc(II) 9,10-dihydroxyoctadecanoates is established by the results of the melting points, elemental analysis, IR and NMR spectra. The electrical conductances of the pure soap and some binary mixtures with the corresponding metal Octadecanoates are measured. It is found that while the plots of logarithm of conductivity against inverse temperature of the lead(II) 9,10-•dihydroxyoctadecanoate (Pb(OH)2A2) show a maximum, that of Zinc(II)9,10-dihydroxyoctadecanoate(Zn(OH)2A2 and its binary mixtures Zinc(II)octadecanoate/Zinc(II)9,10-dihydroxyoctadecanoate (ZnA2/Zn(OH)2A2) are linear. However, for the binary mixtures of lead(II)octadecanoate/lead(II)9,10-dihydroxyoctadecanoate (pbA2/Pb(OH)2A2) at low mole fractions (XPb(OH)2A2 <0.02) non-linear graph characteristics of the behaviour of lead(II) carboxylate systems are observed while for high mole fractions (XPb(OH)2A2 > 0.03) the shape of the curves resemble that of pure Pb(OH)2A2,the observance of a maximum in the system is interpreted in terms of the interaction of lead ions with the hydroxyl groups. Plots of molar volume against temperature for PbA2 /Pb(OH)2A2 show curvature in support of such interactions, suggesting deviations from ideal behaviour of the liquid systems. The activation energies for conduction and dissociation (ΔHKµ +ΔH/3) for the pure lead(II) and Zinc(II)9,10-dihydroxyoctadecanoates and their mixtures are obtained. For lead(II) octadecanoate/ lead(II)9,10-dihydroxyoctadecanoate at low mole fraction the enthalpy decreases steadily up to a point with increase in mole fraction and then increases. However, for the zinc soaps and its mixtures the enthalpy terms are found to be fairly constant with increasing mole fraction even when the actual conductivity falls.
Open Access
Periodate Oxidation of Tris-(4,4'- Dimethyl-2.2' Bipyridine) iron (ii).
(Obafemi Awolowo University, 1986) Ayodele, Ezekiel Temitayo; Ige, W. J.
This work covers the periodate oxidation of tris-(4,4'-dimethyl-2,2'-bipyridine) iron (II) complex. The reactive periodate species postulated from the ionic strength dependence in acid medium are IO3+ H6IO6 or I(OH)6+. In both acid and neutral med the ionic strength dependence of observed rate constant was found to fit into Bronsted Bjerrum Christiansen formulation while in alkaline medium significant deviation was observed. In acid medium, a reaction order of 0.2 obtained with respect to the periodate ion species shows that the reaction proceeds via a complex mechanism. The reaction was found to be acid dependent, and protonation of the periodate or complex occurs prior to electron transfer and the reaction proceeds by outer-sphere mechanism. In alkaline medium, the formation of mesoperiodate and other polymeric species for which the accompanying equilibria are not precisely known makes the reaction more complex and the postulation of a reasonable mechanism impossible. In neutral medium as in acid medium, reaction proceeds through the formation of an outer-sphere complex. At low periodate ion concentration, a stoichiometry of 1:1 with respect to the complex and periodate was obtained while at high periodate ion concentration the stoichiometry is 3:1.
Open Access
Electrical Conductivity and Viscosity of Nigerian Traditional Soaps in Non-aqueous Solvents.
(Obafemi Awolowo University, 1986) Adebajo, Moses Olorunfemi; Akanni, M. S.
The electrical conductance and viscosities of different concentrations of alcoholic solutions of Nigerian traditional soap are measured as a function of temperature. Sodium, potassium and potassium/sodium (50:1) soaps are prepared from palm kernel oils using laboratory reagent alkalis. Their conductances are also measured. While the conductance values vary with the state of purity of the soaps and the polarity of the solvents, no significant change is observed in viscosity in relation to their purity. The conductances of the prepared potassium soaps are found to be higher than those of the prepared sodium soaps, suggesting the metal ions to be the main charge carriers. The plots of logarithm-of conductivity against inverse temperature for all the soaps arc linear in Methanol and ethanol while such plots are non-linear in 1-propanol, a solvent in which the soaps are least soluble with low conductance values. However, the plots of logarithm of viscosity against inverse temperature are linear for the soaps in all the alcohols within the range of the concentration studied. Data are presented for both the activation energy for viscous flow and conductance. In each case, the energy values appear to increase with the molecular weight of the solvents. The viscosity data arc fitted to the Jones-Dole equation and the A and B-coefficients are evaluated. The trend of the values of the 3-coefficients with temperature and polarity of the solvents is discussed. The removal of excess acid/base/water appears to enhance the foaming capability of the soaps. Some other undetermined minor or trace impurities seem to have little or no effect on the foaming efficiency of the traditional soaps.
Open Access
Class Structure and Character Tables of Permutation Groups for Weakly Bound Polymer Molecules and Some Applications.
(Obafemi Awolowo University, 1987) Adekola, Folahan Amoo; Odutola, J. Ade
Permutation and permutation-inversion groups for polymer molecules have been systematically studied. This encompasses review of the permutation and permutation-inversion groups for dimer molecules, followed by extension to trimers, tetramers and higher polymer molecules. Some formulae for determining the conjugacy classes of both the symmetric and non-symmetric polymers are presented. It has been shown that the character tables for the polymer molecules are easy to construct once the feasible operations of the appropriate monomer groups are determined. The Frobenius formula for characters of induced representations and Clifford’s theorem has been used to compute the characters of the irreducible representations of the various polymer groups. The permutation groups for (NH3)3, (C6H6)3 and (NH3)4 have been found to consist of 1296, 10368 and 31104 elements while their various permutation-inversion groups have 2592, 20736 and 62208 elements respectively. The character tables of non-symmetric polymer molecules are relatively much easier to construct. A method for determining the nuclear spin functions and hence the statistical weights is presented using (H20)3 and (NH3)2 as examples. The general theory of the nuclear hyperfine structure has been simplified and this has been used in predicting the possible number of spectral transitions for some molecules.
Open Access
Preparation and Characterisation of Pyrolytically-Deposited Thin Oxide Films from Metal-Organic Compounds
(Obafemi Awolowo University, 1987) Lambi, John Ngolui; Ajayi, O.B.; Akanni, M.S.
A simple and versatile pyrolytic method of preparing thin metal oxide films that is based on the Metal Organic Chemical Vapour Deposition (MOCVD) technique and that is operative at relatively low temperatures (420°C) has been utilised to prepare the thin metal oxide films of indium, zinc, aluminium and copper from the appropriate metal acetylacetonate or carboxylate. To fully understand the pyrolytic route leading to film formation, the thermal decomposition of some of the starting materials was investigated in detail at 420°C in air and N,, using separately, a Muffle furnace and a flow system. The identities of the products as determined by a combination of techniques are Cu, CO2, a carboxylic acid and an odd chain-length alkene, in the case of the copper(II) soaps; ZnO, CO2 and a ketone for the zinc soaps; and a mixture of Cu, Cu20 and CuO in the case of the copper(II) acetylacetonate. While mechanisms have been proposed to account for the degradative routes of the soaps, which of the metal acetylacetonates is still inconclusive. A combination of Ion Beam, X-ray and optical absorption studies have shown that the oxide films of indium, zinc and aluminium are, of the expected stoichiometry, while that of copper is of mixed composition (CuO/Cu2O/Cu). It is not immediately clear why carbon and alkali metal contamination was observed for the Al2O3 and CuO/Cu2O/Cu films but not for the In2O 3 film. Scanning Electron Microscopy (SEM) has shown the films to be polycrystalline. The observed optical characteristics (high transmittances, T = 75-90%; moderate reflectances, R < 21%; low absorbances, A < 8%; high refractive indices, nf > 1.5 and low extinction coefficients, k < 0.4) are as expected for these thin films. Potential uses of these thin layers based on their observed properties are also discussed.
Open Access
Synthesis and neuropharmacological activity of some quinoxalinone derivatives
(Academic Journals, 2007-03-19) Olayiwola, G.; Obafemi, C.A.; Taiwo, F.O
Eight quinoxalinone derivatives were synthesized and investigated for some neuropharmacological effects (analgesia, sedation, convulsion, anxiety, memory and psychosis) in mice and rats. In the CNS depressant activity, N,N-dibenzyl-2,3-dioxo-1,2,3,4-tetrahydroquinoxaline-6-sulfonamide is the most active, while the other compounds appear variously dose-dependent. Only three of the compounds showed anxiolytic effect, with N,N-dibenzyl-2,3-dioxo-1,2,3,4-tetrahydroquinoxaline-6-sulfonamide showing the highest activity at 2.5 mg/kg. At the dose of 30 mg/kg, 6-nitro-1,4-dihydroquinoxaline-2,3-dione showed a better anxiolytic effect in mice than diazepam (dose: 1 mg/kg), while 1,2,3,4-tetrahydroquinoxaline-2,3-dione (dose: 25 mg/kg) showed a comparative effect to diazepam. 6-Chloro-1,4-dihydro-quinoxaline-2,3-dione and N,N-dibenzyl-2,3-dioxo-1,2,3,4-tetrahydroquinoxaline-6-sulfonamide showed significant anticonvulsant action. None of the compounds showed any analgesic or antidopaminergic effect. The LD50 (24 h) calculated for the compounds were between 74 and 160 mg/kg i.p.
Open Access
ATR-FTIR AND HPLC SPECTROSCOPIC STUDIES AND EVALUATION OF MINERAL CONTENT OF CARICA PAPAYA LEAVES AND FLOWERS
(Open Access Scientific Publisher, 2015-02-06) Fadare, O.A.; Durosinmi, O.M.; Fadare, R.; Izevbekhai, O.U.; Awonyemi, I.O.; Obafemi, C.A.
We applied Fourier transform infrared spectroscopy (FTIR) to study the main constituents in the male Carica papaya leaves and flowers in the mid infrared region 4000–650 cm –1. The findings indicated that FTIR spectrum can discriminate and identify various functional groups present in the pawpaw parts. Four water-soluble vitamins, thiamine (vitamin B 1 ), riboflavin (vitamin B 2 ) niacin (vitamin B3) and folic acid (vitamin B9) were analyzed by HPLC. Niacin and folic acid were detected in the leaves at a concentration of 7.08 mg/100 g and 1.00 mg/100 g dry weight, respectively, while only folic acid could be detected in the flowers at a high concentration of 510.34 mg/100 g dry weight. Atomic absorption spectroscopy (AAS) analysis of the samples showed that the leaves and flowers contain elements like K, Na, Mn, Mg, Fe, Zn, Cu, Ca, Cd and Ni in various proportions, with the leaves containing higher concentrations of Mg, Ca, Zn, Fe and Ni than the flowers.
Open Access
Extraction and Identification of Some Antioxidant and Antimicrobial Compounds from Urena Lobata (Linn) Leaves
(2015-03-23) Adeloye, Adewale Olufunsho
This study examined the extract of Urena lobata L. leaves for its antioxidant, antibacterial and antifungal activities with a view to isolating and characterizing the biologically active components that might be present and thus provide justification for the ethnomedicinal uses of the plant in the treatment of various diseases for which it was used. Urena lobata L. leaves were collected, identified and air-dried for 3 weeks after which they were ground into coarse powder and extracted at room temperature with 50% aqueous ethanol for 72 hours with occasional agitation. The filtrate was concentrated to dryness in vacuo on a rotary evaporator to obtain the crude extracts. The crude extract was dissolved in distilled water and then partitioned successively with four different organic solvents which included n-hexane, dichloromethane, ethyl acetate and n-butanol. The solvent fractions obtained were concentrated in vacuo and then evaluated for antibacterial, antifungal activities tests. In another bench-top bioassay antioxidant screening method, all the solvent fractions were screened for antioxidant activity using the rapid thin layer chromatographic method with l,1-diphenyl-2-picrylhydrazyl (DPPH) solution in methanol as detecting reagent. A detailed bioactivity guided fractionation was carried out on the ethyl acetate extract by gradient column chromatography using combination of Accelerated Gradient Chromatographic (AGC) method and Sephadex LH-20 adsorbent. Preliminary evaluation of the crude extract for antibacterial and antifungal activity using Agar-well diffusion method with streptomycin as standard antibiotic showed that the extract had a broad spectrum of activity against both Gram positive and Gram negative bacteria isolates. The ethyl acetate and n-butanol fractions had a fast antioxidant reaction with DPPH solution, while the n-hexane and dichloromethane fractions gave no reaction with the test reagent. Three flavonoid compounds were isolated from the ethyl acetate fraction namely: 1 kaempferol, 2 quercetin, and 3 tiliroside (3-O-β-D-(6"-O-transp-coumaroyl)-α-L-glucopyranosyl-kaempferol). The structures of the flavonoid compounds were determined from spectra obtained on them using infra-red, IH and 13C NMR. The study concluded that the isolated flavonoid compounds were part of the compounds responsible for the biological activity of Urena lobata leaf extract.
Open Access
Detailed Subsurface Structural and Stratigraphic Interpretation of Kunbi Marginal Oil Fleld, Niger Delta, Using Three Dimensional (3-D) Seismic Reflection Data
(2015-04-29) Obaoye, Michael Olajide
The primary objective of this study was to determine the proven, probable and possible oil reserves in the supposedly marginal Kunbi Field as a means of establishing if the oil accumulation in the field is in commercial quantity. The methodology involved the integration of seismic 3-D structural and stratigraphic time interpretation; seismic attributes like reflection intensity, root means square amplitude and complex trace attributes like instantaneous amplitude, instantaneous frequency and phase to maximize information derivation from the field. Depth mapping was integrated with detailed petrophysical analysis to build a static model with constant petrophysical parameters which were used to calculate the reserves. Post well completion nuclear logging using Haliburton's Reservoir Monitoring Tool was conducted to re-establish oil contacts by measuring carbon-oxygen ratio and other elemental yields. Stratamplitude and complex trace attributes were extracted from the interpreted seismic to infer the field's depositional environments and facies. The gamma ray log characteristic shapes were also used in conjunction with reflection geometry and high resolution biostratigraphic studies to completely detail the sequence stratigraphic setting and depositional environment of the field; classify the reservoirs according to sedimentation stacking processes. The interpreted 3-D seismic time maps were then converted to depth maps using the average velocity method while a detailed petrophysical analysis was then integrated with the depth maps to build a static model which was used to calculate the original oil in place and ultimate recoverable reserves. The result of the analysis of stratamp in Excel showed that even though the reservoirs were optimally located structurally at all the eight oil bearing levels, some of them were not optimally located stratigraphic wise and require some lateral shifts from 35 meters up to 247 meters. Integration of seismic reflection geometry, logs' shapes interpretation and Stratamplitude study confirmed that the reservoirs in this depocenter were of shallow marine, deltaic, river mouth siliciclastic sand bars, fluviatile derived, transported and deposited under moderate to high energy regime and wave dominated. The result of the static modelling and the resulting reserves calculation revealed that Kunbi Field proven, probable and possible reserves were in excess of 99.5, 162.4 and 272.2 MMBL STOIIP prior to nuclear logging with Haliburton's Nuclear Reservoir Monitoring Tool compared with the previous estimation of proven reserves of 56.9 MMBL STOIIP using the 2-D seismic data. However, post completion nuclear logging suggested that the probable (P1+P2) reserves can be as high as 256 MMBOL as compared with 162 MMBOL STOIP above. It was concluded that in addition to the proved, probable and possible oil reserves in this field, there were other drillable updip and upside oil potentials within the farmout polygon.
Open Access
Experimental and theoretical studies on some selected ionic liquids with different cations/anions as corrosion inhibitors for mild steel in acidic medium
(Elsevier, 2016-05) Sasikumar, Y.; Olasunkanmi, Lukman O.; Bahadur, Indra; Kabanda, Mwadham M
Inhibition of mild steel corrosion in 1 M HCl solution by some alkylimidazolium-based ionic liquids (ILs) namely 1-ethyl-3-methylimidazolium ethylsulfate [EMIM]+[EtSO4]−, 1-ethyl-3-methylimidazolium acetate [EMIM]+[Ac]−, 1-butyl-3-methylimidazolium thiocyanate [BMIM]+[SCN]−, 1-butyl-3-methylimidazolium acetate [BMIM]+[Ac]− and 1-butyl-3-methylimidazolium dicyanamide [BMIM]+[DCA]− was investigated using electrochemical, spectroscopic, surface morphology, quantum chemical calculations, quantitative structure activity relationship (QSAR) and Monte Carlo simulation methods. The studied ILs showed appreciable inhibition efficiencies within the range of concentrations considered. Polarization measurements showed that the studied ILs are mixed-type inhibitors, that is, they inhibit both the anodic mild steel dissolution and cathodic hydrogen evolution reactions. The adsorption of the ILs on mild steel affords competitive physisorption and chemisorption processes and obeyed the Langmuir adsorption isotherm. Spectroscopic studies confirmed chemical interactions between the ILs and mild steel, while the scanning electron microscopy (SEM) images revealed the formation of protective film of the inhibitors on mild steel surface. Theoretical quantum chemical calculations, QSAR analyses and Monte Carlo simulations studies were used to correlate experimental results. The best fit QSAR equations are functions of molecular weight, fraction of electrons transferred from the inhibitor to the metal and dipole moment of the ILs.
Open Access
Identification and comparison of the volatile constituents of fresh and dried leaves of Spondias mombin found in North-central Nigeria: in vitro evaluation of their cytotoxic and antioxidant activities
(Taylor & Francis publishing, 2016-05-09) Oladimeji, Abdulkabir Oladele; Aliyu, Medinat Bola; Ogundajo, Akintayo Lanre; Babatunde, Oluwatoyin; Adeniran, Oluremi Ishola; Balogun, Olaoye Solomon
Context: Various studies have shown that the leaf extracts of Spondias mombin Linn (Anacardiaceae) possess pharmacological properties such as antioxidant and antiviral effects. However, no biological activity from its essential oil has been reported in literature. Objective: To analyse the chemical constituents, cytotoxic activity and antioxidant capability of the essential oils from fresh and dried leaves of S. mombin. Materials and methods: Hydrodistillation using Clevenger-type apparatus was employed to obtain the essential oil. Oil analysis was performed using an HP 6890 Gas Chromatograph coupled with an HP 5973 Mass Selective Detector. The cytotoxicity bioassay was carried out using the brine shrimp lethality test (10,000-0.01 μg/mL). Additionally, the reactive oxygen species scavenging potential of the two S. mombin oils (1000-200 μg/mL) were investigated using a hydroxyl radical scavenging and ferric iron reducing system. Results: Chemical analysis of essential oils from S. mombin revealed the presence of 41 compounds, with predominance of monoterpenoids, sesquiterpenoids and non-terpenoids derivatives. In both fractions, the principal component was β-caryophellene (27.9-30.9%), followed by γ-cadinene (9.7-12.3%). There was an increase in the oxygenated monoterpenoid contents and a concomitant decrease in the amounts of sesquiterpenoids hydrocarbons observed on drying the leaves. The oil obtained from the fresh leaves was more active than that obtained from dried leaves, with LC50 values (from the brine shrimp lethality assay) of 0.01 and 4.78 μg/mL, respectively. The two oils (from fresh and dried leaves) at 1.0 mg/mL scavenged hydroxyl radical by 83% and 99.8%, respectively. Moreover, they reduced ferric ion significantly and compared favourably with vitamin C. Conclusions: Essential oil derived from the leaves of S. mombin could hold promise for future application in the treatment of cancer-related diseases.
Open Access
Polyphenolic compounds with anti-tumour potential from Corchorus olitorius (L.) Tiliaceae, a Nigerian leaf vegetable
(2016-06) Taiwo, Bamigboye; Taiwo, Grace O.; Olubiyi, Olujide Oludayo; Fatokun, Amos Akintayo
Chromatographic fractionation of the methanolic extract of Corchorus olitorious (L.) (Tiliaceae), on silica gel yielded two polyphenolic compounds. The structures of the compounds were elucidated as Methyl-1,4,5-tri-O-caffeoyl quinate and Trans-3-(4-Hydroxy- 3-methoxyphenyl) acrylic anhydride, based on extensive use of spectroscopic techniques such as 1H and 13C NMR, DEPT and 2D NMR experiments (COSY, HSQC, HMBC), IR and MS. To establish an initial proof-of-concept for the biological relevance of these compounds, their cytotoxicity in the HeLa cell line was assessed as an index of their anti-tumour potential. The compounds when tested at a range of concentrations up to 1.6 mM were found to possess mild cytotoxic activity. The trans-3-(4-hydroxy-3-methoxyl phenyl) acrylic anhydride was found to be related to curcumin, a compound known to have anti-cancer activity. The plant therefore represents a source of natural ‘lead’ compounds with anti-tumour potential
Open Access
A Cytotoxic Indole Alkaloid from Alstonia boonei
(Taylor & Francis publishing, 2016-11-24) Balogun, Olaoye; Ajayi, Olukayode Solomon; Agberotimi, Juliana
Stem bark of Alstonia boonie (1.24 kg) was exhaustively extracted with 95 % aqueous methanol. The crude extract was defatted with n-hexane and thereafter subjected to extensive chromatography to yield Alstiboonine (1) which was fully elucidated and characterised using 2D NMR analysis. Alstiboonine, crude extract and the n-hexane fraction were subjected to brine shrimps lethality test at varying concentrations. The result showed that all the test samples exhibited significant cytotoxicity.