Department of Chemistry

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Open Access
Adsorption characteristics of green 5-arylaminomethylene pyrimidine- 2,4,6-triones on mild steel surface in acidic medium: Experimental and computational approach
(Elsevier B.V, 2018-01-10) Chandrabhan, Verma; Lukman.O, Olasunkanmi; Eno.E, Ebenso; M.A, Quraishi
The effect of electron withdrawing nitro (–NO2) and electron releasing hydroxyl (–OH) groups on corrosion inhibition potentials of 5-arylaminomethylenepyrimidine-2,4,6-trione (AMP) had been studied. Four AMPs tagged AMP-1, AMP-2, AMP-3 and AMP-4 were studied for their ability to inhibit mild steel corrosion in 1 M HCl using experimental and theoretical methods. Gravimetric results showed that inhibition efficiency of the studied inhibitors increases with increasing concentration. The results further revealed that that electron withdrawing nitro (–NO2) group decreases the inhibition efficiency of AMP, while electron donating hydroxyl (–OH) group increases the inhibition efficiency of AMP. SEM and AFM studies showed that the studied compounds inhibit mild steel corrosion by adsorbing at the metal/electrolyte interface and their adsorption obeyed the Temkin adsorption isotherm. Potentiodynamic polarization study revealed that studied inhibitors act as mixed type inhibitors with predominant effect on cathodic reaction. The inhibitive strength of the compounds might have direct relationship electron donating ability of the molecules as revealed by quantum chemical parameters. The order of interaction energies derived from Monte Carlo simulations is AMP-4 > AMP-3 > AMP-2 > AMP-1, which is in agreement with the order of inhibition efficiencies obtained from experimental measurements.
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
Chemical Composition and In-vitro Antibacterial Activity of the Essential Oil of Nigerian Moringa oleifera Lam. Flowers
(SCIENCEDOMAIN international, 2017-03-02) Balogun, O.S.; Fadare, R.Y.; Fadare, O.A.; Akinpelu, D.A.; Obafemi, C.A.
Aims: To investigate the chemical composition and antibacterial activity of essential oil isolated from flowers of Moringa oleifera (MO) grown in Western Nigeria. Methodology: Gas chromatography–mass spectrometry (GC-MS) analysis was carried out for identification and determination of the phytochemical constituents of the oil. Standard microbiological methods was also employed to evaluate the antibacterial activities of the oil. Results: GC-MS analysis revealed a total of twenty-five phytochemical constituents, with the major constituents found to be nonanal (17.3%), trans-geranyl geraniol (13.5%) and eicosane (12.3%), α- terpineol (7.2%), methyl palmitate (4.6%) and methyl octadec-9-enoate (4.1%). The antibacterial assay, using standard microbiological methods, showed that the oil had inhibitory effects against both Gram-positive (Bacillus cereus, Micrococcus luteus and Staphylococcus aureus) and Gramnegative (Escherichia coli and Pseudomonas aeruginosa) bacteria isolates. The minimum inhibitory concentrations (MICs) exhibited by the essential oil against test bacteria ranged between 1.25 mg/mL and > 5 mg/mL. Conclusion: Essential oil of Nigerian Moringa oleifera flowers contains biologically active ingredients and possess some level of antibacterial activity. The oil can be a good source of antibacterial agents.
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
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
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
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
Corrosion inhibition of mild steel in 1M HCl by D-glucose derivatives of dihydropyrido [2,3-d:6,5-d′] dipyrimidine-2, 4, 6, 8(1H,3H, 5H,7H)-tetraone
(Nature publishing, 2017-02-07) Verma, Chandrabhan Verma; Quraishi, Mumtaz Ahmad; Kluza, Kamil; Makowska-Janusik2, M.; Olasunkanmi3, Lukman O.; Ebenso, Eno E.
D-glucose derivatives of dihydropyrido-[2,3-d:6,5-d′]-dipyrimidine-2, 4, 6, 8(1H,3H, 5H,7H)-tetraone (GPHs) have been synthesized and investigated as corrosion inhibitors for mild steel in 1M HCl solution using gravimetric, electrochemical, surface, quantum chemical calculations and Monte Carlo simulations methods. The order of inhibition efficiencies is GPH-3 > GPH-2 > GPH-1. The results further showed that the inhibitor molecules with electron releasing (-OH, -OCH3) substituents exhibit higher efficiency than the parent molecule without any substituents. Polarization study suggests that studied compounds are mixed-type but exhibited predominantly cathodic inhibitive effect. The adsorption of these compounds on mild steel surface obeyed the Langmuir adsorption isotherm. SEM, EDX and AFM analyses were used to confirm the inhibitive actions of the molecules on mild steel surface. Quantum chemical (QC) calculations and Monte Carlo (MC) simulations studies were undertaken to further corroborate the experimental results.
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.
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
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
Electrochemical detection of Epinephrine using Polyaniline nanocomposite films doped with TiO 2 and RuO 2 Nanoparticles on Multi-walled Carbon Nanotube
(Elsevier publisher, 2017-05-10) Tsele, Tebogo P.; Adekunle, Abolanle; Fayemi, Omolola E; Ebenso, Eno
Electrochemical properties of functionalized MWCNT/polyaniline doped with metal oxide (TiO 2 , RuO 2 ) nanoparticles were explored. Successful synthesis of MWCNT, TiO 2, RuO 2 , PANI, MWCNT-PANI-TiO 2 , and MWCNT-PANI-RuO 2 nano materials were conﬁrmed using suitable characterization techniques. Successful modiﬁcation of gold (Au) electrode with these nanoparticles was conﬁrmed using electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy. Au-MWCNT-PANI-TiO 2 and Au-MWCNT-PANI-RuO 2 gave the best electron transport properties towards the oxidation of epinephrine (EP) compared with other electrodes investigated. The Tafel values 0.448 and 0.442 V/decade for Au-MWCNT-PANI-TiO 2 and Au-MWCNT-PANI-RuO 2 electrodes respectively in (EP) suggest adsorption due to analyte oxidation intermediates products. The linear calibration plot was obtained for EP at concentrations range 4.9 to 76.9 m M. The limits of detection of EP were estimated to be 0.16 and 0.18 m M for Au-MWCNT-PANI-TiO 2 and Au-MWCNT-PANI-RuO 2 electrodes respectively. The interference study using DPV showed clear peak separation for amino acid (AA) and EP. Therefore, the modiﬁed electrodes can selectively detect epinephrine without interference from ascorbic acid signal. The analytical performance of the fabricated sensors has been evaluated for detection of epinephrine (EP) in a pharmaceutical sample with satisfactory results
Open Access
Electrochemical determination of serotonin in urine samples based on metal oxide nanoparticles/MWCNT on modiﬁed glassy carbon electrode
(Published by Elsevier B.V, 2017-01-11) Fayemi, Omolola E.; Adekunle, Abolanle S.; Ebenso, Eno E.
The electrochemical response of serotonin on the modiﬁed electrode based on multiwalled-carbon-nanotube (MWCNT) doped respectively with nickel, zinc and iron oxide nanoparticles coating on glassy carbon electrode (GCE) at physiological pH 7 was determined using cyclic voltammetry (CV) and square wave voltammetry (SWV). The modiﬁed GCE/MWCNT-metal oxide electrodes exhibited excellent electrocatalytic activity towards the detection of serotonin at large peak current and lower oxidation potentials compared to other electrodes in- vestigated. The dynamic range for the serotonin determinationwas between 5.98 × 10 −3 μM to 62.8 μMwithde- tection limits 118, 129 and 166 nM for GCE/MWCNT-NiO, GCE/MWCNT-ZnO and GCE/MWCNT-Fe 3 O 4 sensors respectively. GCE-MWCNT-NiO was the bestelectrode in terms of serotonin currentresponse, electrode stability, resistance to fouling and limit of detection towards the analyte.The developed sensors were found to be electro- chemicallystable, reusable, economically effective due to theirextremely low operational cost, and have demon- strated good limit of detection, sensitivity and selectivity towards serotonin determination in urine samples. © 2017 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).
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
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
High level leaching of heavy metals from colorful ceramic foodwares: a potential risk to human
(Springer publishing, 2017-06-05) Aderemi, Taiwo Adedoyin; Adenuga, Adeniyi Abiodun; Oyekunle, John Adekunle Oyedele; Ogunfowokan, Aderemi Okunola
Abstract Ceramic foodwares are among the products used by people on daily basis without being cautious of exposures to heavy metals through possible leaching from the glaze ce- ramics. This study investigated the levels of heavy metals foundinsomecommonlyusedceramicfoodwaresin Nigeria with the aim of determining levels of human expo- sures through the use of the ceramics. To achieve this, acid digestion was carried out for the total metal concentrations and leaching tests were done using 4% acetic acid as a leaching agent. Metal concentrations were quantified using flame atomic absorption spectrometry (FAAS) and particle-induced X-ray emission spectrometry (PIXES) analysis. All the ceram- ic foodwares studied were found to contain varied amounts of heavy metals in their glazes, with concentrations in the range of 26.45–2071.46, 5.20–547.00, 1.24–2681.02, 2590.00– 8848.40, 6.42–654.66, 112.69–649.95, 63.38–2518.51, and 3786.51–8249.44 μgg −1 for Pb, Cd, Zn, As, Cu, Cr, Mn, and Fe, respectively. Concentrations of the metals leached from the ceramics were in the range of 0.11–0.97, 0.01– 0.28, 0.00–4.19, 1.93–15.00, 0.01–0.41, 0.09–0.60, 0.01– 2.14, and 0.01–11.53 mgL −1 for Pb, Cd, Zn, As, Cu, Cr, Mn, and Fe, respectively. Comparing the ratio of the metals leached from the ceramic wares with those of the metal oxides in the ceramics, it was noticeable that not all the metals de- tected in the ceramic samples were domiciled in the glaze but in the clay materials used for the ceramics.
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
In vitro antioxidant activity and gas chromatographymass spectrometry analysis of solvent extracts of Kigelia africana stem bark
(2017-07-20) Obafemi, C.A.; Fadare, O.A.; Balogun, O.; Obuotor, E.M.; Fadare, R.Y.; Ojo, O.D.
Objective: Kigelia africana is widely used, traditionally, in Africa in the treatment of many conditions and complaints such as kidney and stomach disorders, malaria, wounds, and venereal diseases. In the present study, an attempt has been made to investigate the antioxidant activity of extracted fractions of the stem bark and analyze the non-polar fractions for the presence of various components that may be responsible for their antioxidant properties. Methods: The antioxidant activity was evaluated using 1,1-diphenyl-2-picrylhydrazyl, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation and nitric oxide radical scavenging models. Analysis of the chemical components of the solvent extracts was carried out by gas chromatography-mass spectrometry (GC-MS). Results: Strong activity (71-89% inhibition) was found for the ethyl acetate fraction, whereas the non-polar chloroform fraction exhibited a relatively weak activity (24-48%) inhibition, at 25 μg/ml concentration. GC-MS analysis of the non-polar extracted fractions identified 21 and 12 compounds for the hexane and chloroform fractions, respectively, of which α-terpineol (2) (39.21%) was the main component identified for the hexane extract, and α-amyrin (9) (32.54%) was the main component identified for the chloroform extract. Conclusion: This study shows that the non-polar extracted fractions of K. africana stem bark may be a potential source of natural antioxidants or bioactive agents.
Open Access
Isolation,characterization,crystalstructure, freeradicalscavenging-andcomputational studiesof...
(Elsevier publishing, 2017-05-13) Agunbiade, Rachael Y.; Jasinski, Jerry P.; Millikan, Sean P.; Sanusi, K; Ceylan, Ü; Fadare, Olatomide A.; Obafemi, Craig A.; Yilmaz, Y
A new crystallographic form of a pure xanthenedione derivative (110), C22H24O3, was isolated from thehexane extract of the seeds ofGarcinia kola. The structure of the compound was determined on the basisof FTIR and NMR spectroscopy and confirmed by single-crystal X-ray diffraction analysis. The compoundcrystallized as C22H24O3H2OH3OþCl , as the result of the extraction process, adopts monoclinic, spacegroup P21/n (no. 14) and is stabilized by OWeH/OW, OWeH/Cl, CeH/OW, CeH/Cl intramolecularhydrogen bonds and weak OWeH/O, CeH/O, intermolecular interactions forming a 3-D supramo-lecular structure. The molecular property of the pure xanthene derivative, C22H24O3, has also beeninvestigated using the density functional theory (DFT) method. The calculated IR,1H and13C data werefound to be in good agreement with experimental values. The compound C22H24O3showed weak DPPHradical scavenging activity with IC50value of 2.37±0.08 mg/ml.