Department of Chemistry- Journal Articles

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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
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
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.
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
Synthesis Characterization and Biological Activities of Coordination Compounds of 4-Hydroxy-3-nitro-2 H -chromen-2-one and Its Aminoethanoic Acid and Pyrrolidine-2-carboxylic Acid Mixed Ligand Complexes2016
(Hindawi Publishing, 2017-02-07) Aiyelabola, Temitayo; Akinkunmi, Ezekiel Olugbenga; Obuotor, Efere Martins; Idowu, Olawuni
Coordination compounds of 4-hydroxy-3-nitro-2 H -chromen-2-one and their mixed ligand complexes with aminoethanoic acid and pyrrolidine-2-carboxylic acid were synthesized by the reaction of Cu(II) and Zn(II) salts in molar ratio 1 : 2 for the coumarin complexes and 1 : 1 : 1 for the mixed ligand complexes, in basic media. The compounds formed were characterized using infrared, Uv-vis spectrophotometric analyses, mass spectrometry, magnetic susceptibility measurements, and EDX analyses. It was concluded that 4-hydroxy-3-nitro-2 H -chromen-2-one coordinated as a monobasic ligand for all the complexes; it also coordinated via the carbonyl moiety in the case of the Cu(II) mixed ligand complexes. Similarly it was proposed that the amino acids also coordinated in a bidentate fashion via their amino nitrogen and carboxylate oxygen atoms. The synthesized compounds were screened for their antimicrobial and cytotoxic activities. The complexes exhibited marginal antimicrobial activity but good cytotoxic activity.
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
Syntheses, Characterization, Resolution, and Biological Studies of Coordination Compounds of Aspartic Acid and Glycine
(Hindawi Publishing, 2017-02-15) Aiyelabola, Temitayo; Akinkunmi, Ezekiel Olugbenga; Obuotor, Efere Martins; Adebajo, Adeleke Clement; Isabirye, David
Enantiomerically enriched coordination compounds of aspartic acid and racemic mixtures of coordination compounds of glycine metal-ligand ratio 1 : 3 were synthesized and characterized using infrared and UV-Vis spectrophotometric techniques and magnetic susceptibility measurements. Five of the complexes were resolved using (+)- cis -dichlorobis(ethylenediamine)cobalt(III) chloride, (+)-bis(glycinato)(1,10-phenanthroline)cobalt(III) chloride, and (+)-tris(1,10-phenanthroline)nickel(II) chloride as resolving agents. The antimicrobial and cytotoxic activities of these complexes were then determined. The results obtained indicated that aspartic acid and glycine coordinated in a bidentate fashion. The enantiomeric purity of the compounds was in the range of 22.10–32.10%, with (+)- cis -dichlorobis(ethylenediamine)cobalt(III) complex as the more efficient resolving agent. The resolved complexes exhibited better activity in some cases compared to the parent complexes for both biological activities. It was therefore inferred that although the increase in the lipophilicity of the complexes may assist in the permeability of the complexes through the cell membrane of the pathogens, the enantiomeric purity of the complexes is also of importance in their activity as antimicrobial and cytotoxic agents.
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
Phthalocyanine Doped Metal Oxide Nanoparticles on Multiwalled Carbon Nanotubes Platform for the detection of Dopamine
(Springer publishing, 2017-03-03) Mphuthi, Ntsoaki; Adekunle, Abolanle S.; Fayemi, Omolola E.; Olasunkanmi, Lukman O.; Ebenso, Eno E.
The electrocatalytic properties of metal oxides (MO=Fe3O4, ZnO) nanoparticles doped phthalocyanine (Pc) and functionalized MWCNTs, decorated on glassy carbon electrode (GCE) was investigated. Successful synthesis of the metal oxide nanoparticles and the MO/Pc/MWCNT composite were confirmed using UV-Vis, EDX, XRD and TEM techniques. Successful modification of GCE with the MO and their composite was also confirmed using cyclic voltammetry (CV) technique. GCE-MWCNT/ ZnO/29H,31H-Pc was the best electrode towards DA detection with very low detection limit (0.75μM) which compared favourably with literature, good sensitivity (1.45μA/μM), resistance to electrode fouling, and excellent ability to detect DA without interference from AA signal. Electrocatalytic oxidation of DA on GCE-MWCNT/ZnO/29H,31H-Pc electrode was diffusion controlled but characterized with some adsorption of electro-oxidation reaction intermediates products. The fabricated sensors are easy to prepare, cost effective and can be applied for real sample analysis of dopamine in drug composition. The good electrocatalytic properties of 29H,31H-Pc and 2,3-Nc were related to their (quantum chemically derived) frontier molecular orbital energies and global electronegativities. The better performance of 29H,31H-Pc than 2,3-Nc in aiding electrochemical oxidation of DA might be due to its better electron accepting ability, which is inferred from its lower ELUMO and higher χ.
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
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.
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
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
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
Proton-induced X-ray emission (PIXE) analysis of trace elements of total atmospheric deposit (TAD) around a smelting industry:
(Taylor & Francis Group, 2018-01-25) Chigaekwu Godwin, EZEH; Paul Jerimiah, UGWO; Mayowa Festus, ADEBIYI; Emmanuel Olawale, ABIYE; Azuka Chinwe, ONWUDIEGWU; Ikechi Eusebius, OBIAJUNWA
This study monitored total atmospheric deposit (TAD) around a smelting plant in Ile-Ife, Nigeria to assess the contributions of the industry to Nigeria’s air-shed pollution. Samples were collected for 12 consecutive months using an Australian model gauge, harvested after 30 d of exposure, filtered and dried to constant weights using oven. Monthly deposition rates were determined and elemental characterizations of the TAD samples were done using proton-induced X-ray emission technique. Results revealed that the monthly deposition rates ranged from 0.69 to 4.62 gm¡3 and was more pronounced in Harmattan. Twenty-three elements were detected; their total elemental concentrations ranged from 1.23 to 13.63 mg m¡3 with Fe having the highest concentrations, while Na has the least. Pearson correlation indicated that some elements have common sources and/ or similar chemical properties; enrichment factor showed that Fe, Zn, Pb, Mn were extremely enriched in the study area, modified degree of contamination (3.75) and pollution load intensity (1.21) showed that the neighborhoods could be exposed to high air pollution related impacts. Positive matrix factorization model revealed three distinct sources: Smelting emission (63%), biomass burning (17%), and suspended input material emissions (21%). The study concluded that the smelting activities posed a great hazard to receptors around the smelting industry.
Open Access
Potential of Ripe Plantain Fruit Peels as an Ecofriendly Catalyst for Biodiesel Synthesis
(MDPI, 2018-02-05) Anietie. O, ETIM; Eriola, BETIKU; Sheriff. O, AJALA; Peter. J, OLANIYI; Tunde. V, OJUMU
The present work was aimed at assessing the possible use of ripe plantain fruit peel as a green-base catalyst in synthesizing Azadirachta indica oil methyl esters (AIOME). The free fatty acid content of the oil (5.81 wt %) was initially reduced to 0.90 wt % using methanol: oil at 2.19 v/v, Fe2(SO4)3 at 6 wt %, time of 15 min and temperature of 65 C. The pretreated oil was converted to AIOME in a transesterification process with calcined ripe plantain peel ash (CRPPA) at 700 C as catalyst. The process was modeled by artificial neural network and optimized using genetic algorithm. The effectiveness of the developed CRPPA is ascribable to its high K content and microstructural transformation. The reliability of the model obtained was confirmed with a high coefficient of determination (R2) of 0.996 and a low mean relative percentage deviation (MRPD) of 8.10%. The best operating variables combination for the process was methanol:oil of 0.73 v/v, CRPPA of 0.65 wt % and time of 57 min while the temperature was kept constant at 65 C with a corresponding AIOME yield of 99.2 wt %. The results of this work demonstrated the potentials of ripe plantain peels and neem oil as cheap feedstocks for biodiesel production