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SYNTHETIC STUDIES ON STEROIDAL ALKALOIDS
(1966) ADEGOKE, E. A.
In the first part of this thesis, a brief survey of the chemistry of veratramine viz. its occurrence, isolation and structural diagnosis is given. This part also includes a review of recent work on the stereochemistry and the synthetic work of other workers on the alkaloid. The main section describes three approaches to the synthesis of the C-Nor-D-homo ring system of the veratrum alkaloids. Howell and Taylor’s acetate diester 6(β-acetoxy-1 β:2αdi (methoxy carbonyl methyl)-9β-methyl-trans decalin prepared from 2:3:4:9:10:12- hexahydro-6-methoxy-12-methyl-2-oxophenanthrene was successfully cyclised to the potential intermediate 6(β -acetoxy-1 β:2α-( cyclopen- tan-3-one)-9-methyl-trans decalin. The pentanone was ring extended to give a solid substance which certainly contained the steroidal ring system of veratramine but which could not be obtained in the pure form. Attempts aimed at an easier preparation of the pentanone acetate by alkylating 1-oxo-6-ethoxy-8a-methyl-1,2,3,7,8, 8a hexahydro naphthalene with different alkylating agents were unsuccessful, the starting material being recovered in each case. In a second approach, 1-(2-cyanoethyl)-2-hydroxy naphthalene was converted to 2:3:4:9:10:12-hexahydro-6-methoxy-7-(3-bromo- propyl)-12-methyl-2-oxophenanthrene and 8-oxo-10a-methyl-1,2,3,4,5,6,8,9,10,10a-decahydro-1-oxa chrysene. The benzene nucleus of either intermediate was resistant to reduction and so they could not be used for further work. In the last attempt, 2-benzoyloxy-1,2,3,4,5,6,7,9,10,11,12,13 dodecahydro-12-methyl-7-oxophenanthrene was prepared starting with 2-naphthol and the tricyclic enone was successfully condensed with 2,2-ethylenedioxy-5-bromo pentan-2-one in the presence of potassium t-butoxide in t-butanol. The adduct was successively reduced, reacted with methyl magnesium bromide, deketalized y acetylated, ozonised and cyclised to give an oily substance which contained the veratramine steroidal nucleus as revealed by its U.V. spectrum. The oil did not crystallize. An oil which should probably crystallize more readily could be obtained if complete reduction of the original ansaturated adduct could be accomplished in the attempts some new compounds were prepared. These were mainly naphthalene, phenanthrene and hydrochrysene compounds. I.R U.V, or N.M.R. spectroscopic data were recorded for all the new compounds and for most of the known ones. Some structural formulae are repeated in the script, so as to aid the reader’s comprehension.
THE CHEMISTRY OF SOME EXTRACTIVES FROM PLANTS OF THE FAMILY RUTACEAE
(1970-05) ABE, M. O.
Chemically, the Rutaceae family is probably the most versatile of all higher family of plants. Three main groups of compounds, namely, limonoids, coumarins and quinoline alkaloids have been obtained from this family. The LLtroductory part of this work reviews very briefly the chemistry of each of these groups. In the main work, three plants of the West African genera of the Rutaceae were investigated. The wood of Afraegle peniculata (Schum and Thonn) yielded the furocoumarin, imperatorin which was isolated earlier from a number of Rutaceous plants and in addition, a furoquinoline alkaloid, dictamnine which had also been isolated from a large number of other genera of the family. The root of Clausena aniaata was shown to contain imperatorin along with a new coumarin (coumarrayin) which was shown almost at the same time by Dreyer to be a constituent of Murraya paniculata. From the wood of Oricia suaveolens was isolated a new alkaloid related to Flindersine (an alkaloid from an Australian Rutaceae plant) The structure of the new alkaloid was elucidated from spectroscopic studies to be 1-methyl-6, 7-dimethoxy-flinderslnc and this structure was confirmed synthetically.
PHYSICOCHEMICAL STUDIES OF SOME TRIVALENT METAL β-DIKETONATES
(1976-06) ADIMADO, A. A.
Forty trivalent metal chelates of 2-thenoylacetone,2 thenoyltrifluoroacetone, 2-furoylacetone, 2-furoyltrifluoroacetone. benzoylacetone, benzoyltrifluoroacetone and nicotinoyltrifluoro— acetone (where metal(Hl) = Al, Crf Mn, Fe and Co) as well as some mixed ligand p-diketonate complexes of iron(IH), have been prepared and their spectroscopic and magnetic properties have been examined. Among the series of compounds studied, Al(fbd) Mn(fbd)3, AKtftbd), Co(tftbd)3, Cr(tffbd)3, Mn(tffbd)3, Co(tffbd)3, M(tbd)3, M(tfpybd)3 (where M = Al, Cr, Mn, Fe and Co ), Fe(bzac)2 (tftbd), Fe(tftbd)2(bzac), Fe(fbd)2(tbd)and Fe(tbd)2(fbd) have been investigated for the first time. The effects of 3-pyridyl, 2-thienyl, 2-furyl, phenyl and trifluoromethyl substituents have been discussed in relation to the lowest spin-allowed transition, п3- п4 and M-O,VC--O and VC--C-—C stretching vibrations. Substitution of a methyl group in 2,4-pentanedione - by a furyl ring, and a methyl group in 1-(2-furyl )-l,3-butanedione by a trifluoromethyl are found to strengthen the C---O and C —C—C and weaken the M—0 bonds of the chelate rings; while the 2-thienyl group shifts the M—O and C -- 0 to lower, and C---C to higher frequencies. The phenyl substituent, as expected, strengthens the M-O and C---C bonds and weakens the C--O bonds. The most sensitive M-0 stretching modes follow the order Co(lII) >A1(III) > Cr(III)> Mn (III) > Fe (III). However, the lowest spin-1llowed п3- п4 translation of the β-ketoenolate anion, although found to be metal sensitive, does not follow the same trend. Trifluoromethyl group substitution resulted in the bathochromic shift of the п3- п4 transitions. The ligand field energy parameters Dq,f (ligand)), B35 and β35 have been calculated and the following order of nephelauxetic effect in the ligands has been derived: Htffbd > Htbd > Hfbd > Hacac > Hbztfac > Htftbd > Hbzac > Htfpybd. While the spectrochemical series of the ligands depicted by the magnitude of f(ligand) parameter also follow:'.the orders tfpybd < bztfac < fbd < tffbd < tbd < acac ~ bzac < tftbd. The reflectance spectra and magnetic properties of these compounds revealed that they are very similar to the corresponding tris—(2,4—pentanedionato) metal(III) octahedral complexes.
KINETICS AND THERMODYNAMIC STUDIES OF NADP BINDING REACTIONS OF GENETIC VARIANTS OF HUMAN ERYTHROCYTE GLUCOSE 6-PHOSPHATE DEHYDROGENASE
(1978-12) ADEDIRAN, S. A.
Inherited Glucose-6-Phosphate dehydrogenase (G6PD) deficiency in humans results in hemolytic anaemia. The enzyme G6PD provides a crucial link in a series of biochemical reactions which occur in the red blood cell that leads to the steady state accumulation of NADPH, reduced glutathione by glutathione reductase, and the removal of potentially dangerous organic peroxides which, if not scanvenged, may result in the formation of radical species of oxygen which damage the energy generation system, which in turn may result in swelling, lysis and hemolytic anaemia. The objective of this thesis was to investigate the human variants of the enzyme G6PD in order to provide a better understanding of the molecular basis of the enzyme activity and factors affecting the onset of the human disease. Human Erythrocyte Glucose-6- Phosphate dehydrogenase has been known to occur in many genetic variants and the catalytic active enzyme of each variant are tetramers and dimers in acidic and alkaline solution respectively. The question then is whether there would be differences in the reactivities of these variants and whether there are differences in the reactivities of the two active forms of the enzyme from the same variant. A comparative analysis of the kinetic and thermodynamic studies of NADP+ binding reactions of these variants under controlled and well-defined experimental conditions of pH and ionic strength was therefore undertaken. The binding reaction of NADP+ to G6PD B+ was also studied as a function of ionic strength of the buffers in order to evaluate the effect of these variations in the buffer system on the co-operative interactions of the NADP+ binding sites on the enzyme. The findings show that there are two binding sites on each of the enzyme variants and these were identified as imidazolium groups of histidine and sulfhydryl groups. The logKm versus pH curves show a broad plateau between pH 6.7 and 8.2 interrupted by a sharp minimum at pH 7.1 for all the enzyme variants. An explanation of this behaviour in terms of co-operative ionization of groups on the enzyme and enzyme-substrate complex which may be linked to the association - dissociation behaviour of the enzyme is proposed. In agreement with G6P binding data, the plot of the enthalpy of the dissociation of enzyme - NADP+ complex against pH shows the shape of a two U—shaped curves consistent with the existence of a tetrameric form of enzyme at acidic pH and dimeric form at alkaline pH. A similar plot of the activation energy of the reaction for each variant shows a consistent decrease of the activation energy with increase in pH, the activation energy at the pH 5.8 being almost halved at the alkaline pH of 9.0, This behaviour is explained to arise from the dimer enzyme being more reactive than the tetramer. There are two schools of thought about the existence and nature of cooperativity among the NADP+ binding sites on G6PD subunits. The study reported in this thesis has unequivocally solved the controversy between the two schools. It is now established that the tetrameric form of the enzyme shows no Cooperativity while the dimeric form is cooperative. The disagreement between the two schools of thought has been explained in the variable experimental conditions used by the workers in the two schools. We have shown that an experimental condition that favours tetramer formation therefore favours non-cooperativity while a condition that favours dimer formation favours cooperativity. The inhibition study by primaquine phosphate shows a complex interaction of this effector with G6PD. There is activation of the G6PD activity at low effector concentration and inhibition at high concentration. This interaction may be due to oxidation of NADPH at low primaquine concentration resulting in generation of more NADP+ which increases the activity of the enzyme. Such a situation might account for the increased hemolysis in variant subjects with low Artracellular NADPH concentration which will result in low level of reduced glutathione. Reduced glutathione is necessary for the maintenance of the integrity of the red cells.
NEW CHROMONE ALKALOIDS FROM THE ROOT -BARK OF SCHUMANNIOPHYTON MAGNIFICUM (HARMS)
(1981-09) ADEBOYE, J. O.
The chemical investigations of some representative alkaloids of Rubiaceae are reviewed. The total syntheses of emetine and quinine are also reviewed while the biogenesis of anthraquinones and biosyntheses of chromones, nicotinic acid 'and nicotine are outlined. The bronchiodilator activities of Khellin and some chromone derivatives are compared and a brief review of the pharmacological activities of a few of the Rubiaceous alkaloids is given. From the methanol extract of the root-bark of Schumanniophyton magnificum, a well known chromone, 5, 7-dihydroxy-2-methylchromone (noreugenin) 97 was isolated in addition to five alkaloids designated SRB2, SRB3, SRB(3)’, SRB(3)" and SRB(4). The constitutional formulae of two of these alkaloids, schumannificine (SRB ) 4 -138 and N-methylschumannificine (SEB(3) 147, have been shown to be new linear tetracyclic compounds with ring D being piperidine in nature on the basis of the chemical evidence and spectral analyses. SRB(2) has been shown to be identical in physical and spectral properties with the product of dehydrogenation of schumannificine (SRB(4) which was named dehydroschumannificine 142. The synthesis of dehydroschumannificine 142 was attempted , This was done in order to correlate the structure that was assigned to it with the natural alkaloids, schumannficine 138and N-methylschumannificine 147, but only the first intermediate, 2,4,6-trihydroxynicotinophenone no 146 was obtained. It was characterised by its spectral properties. The spectral properties of SEB(2)' and SEB(3)" are discussed briefly arid since no conclusive work has been done on then they are tentatively assigned structures 148 & 149 respectively on the basis of their spectral, data.
STUDIES ON THE EFFECT OF SOLVENT ON THE THERMODYNAMICS AND KINETIC REACTIVITY OF GENETIC VARIANTS OF HUMAN ERYTHROCYTE GLUCOSE-6-PHOSPHATE DEHYDROGENASE WITH G6P
(1984-10) ABUGO, O. O.
The characterization of a new variant G6PD, "Mould", has been evaluated in terms of the kinetics and thermodynamics of the binding of G6P to the new enzyme. This enzyme in comparison with G6PD B, is a new variant associated with a slow electrophoretic mobility and a slightly higher red cell G6PD activity. The variation of the kinetic and thermodynamic parameters with pH are however similar suggesting that the structural locus is not part of the binding site for G6P, but away from it. Comparison of the properties of the Mould enzyme with other known G6PD variants found in West Africa has also established the fact that the Mould enzyme is a new sporadic variant in the region. Negative cooperativity was observed for the binding of G6P to the B and Mould G6PDs. Previous kinetic data on G6P binding had given normal Michealian kinetics due to the concentration range of G6P utilized. kmG6P(2), the Km for the high affinity state of the enzyme was found to be similar to the previously determined KmG6P, implying that kinetic measurements had previously been determined at concentrations where binding will be only at the high affinity site for G6P binding on the enzyme. Since G6PD dissociates to the inactive monomer at' high G6P concentrations, the observed negative cooperativity was therefore associated with the probable mechanism by which dissociation of the-enzyme to the inactive form is prevented by the enzyme changing to a conformation with a lower affinity for G6P, The thermodynamic and kinetic functions of the G6P binding reactions have also been determined for G6PD B in water-glycerol mixtures, water, and D(2)0. In the presence of glycerol, the observed sigmoid kinetics was abolished. This behaviour is probably due to the de-formation of one of the G6P binding sites, due to pertubations of protein hydration in the presence of glycerol. Log V(max) is a linear function of dielectric constant and surface tension max: while V(max) is a linear function of viscosity. These correlations show a strong dependence of V(max) on the properties of the bulk solvent. Motive type compensation has been observed, implicating the existence of "linkage process" in G6PD reactions. For the experiments in water and D(2)0, anomalous behaviour was observed for the kinetic and thermodynamic functions of the enzyme at the temperature of maximum density for water (4.0°C) and D(2)0 (11,0°C) Correllation of V(max) and K(m) values of the enzyme with temperature, and therefore mass composition of the solvents showed that these parameters are dependent on the mass composition. Linear dependence of on viscosity of water was observed until at 4.0°C, where there was a discontinuity. Km and V(max) were also strongly dependent on the internal pressure of the two solvents. All these observations do therefore suggest that the catalytic properties of the G6PD enzyme are dependent on the intrinsic properties of the solvent in which it functions, implying that the solvent plays an important role in the catalysis of the enzyme.
PETROLEUM HYDROCARBONS POLLUTION OF NIGERIAN WATERS AND SEDIMENTS AROUND LAGOS AND NIGER DELTA AREA OF NIGERIA
(1989-03) ADEKANMBI, O. E.
There is a paucity of scientific data on the levels and pattern of distribution of petroleum hydrocarbons in the Nigerian aquatic environment. The levels of total hydrocarbons in 241 water and 222 sediment samples in’ the major river systems draining into Nigerian coastal environment around Lagos and the Niger Delta area have been used to monitor the pattern of distribution of hydrocarbons within these areas over different weather regimes during 1984-85. The Utorogu pipeline oil spillage incident in Bendel State of Nigeria in 1984 was used as a case study for assessment of environmental impact of oil spillage in aquatic ecosystem in Nigeria. Samples were also collected and analyzed for total hydrocarbons from Kaduna (Northern Nigeria) and Ibadan (Western Nigeria) for comparative information and controls respectively. Water samples were analyzed for petroleum hydrocarbon by infrared (IR) and gas chromatographic (GC) techniques whereas sediment samples were analyzed by gravimetry and gas chromatography (GC). The infrared (IR) results for 1984 (wet season) showed that Lagos and Lekki lagoons had hydrocarbon level (presented as range followed by mean value in bracket), 1.64-11.40 (5.60) mg/1; Niger Delta, ND (net detectable)-70.70 (6.18)mg/1; Utorogu 0.17-10.50 (2.22)mg/1; Kaduna 4.30-9.90 (6.98)mg/1, while Ibadan water samples (serving as control area) showed no detectable levels of hydrocarbon. In 1985 (dry season) there was a decrease in the hydrocarbon levels found in the water samples. Lagos and Lekki lagoons recorded 0.10-0.41 (0.25)mg/1; Niger Delta 0.10-1.80(0.52)mg/1 and Utorogu 0.17-4.67 (2.14)mg/1. The gas chromatographic values for hydrocarbon concentration in water were much lower than the infrared values. All the samples except Upomani discharge point (3.36 mg/1) had values below 1 mg/1 by GC. Nonetheless, the IR values correlated well with the GC values. The corresponding hydrocarbon levels (on dry weight basis) in sediment samples in 1984 were: Lagos and Lekki lagoons ND-95.54 (30.33) µg/g; Niger Delta ND-74.05 (9.09) µg/g; Utorogu 14.04- 267.48 (98.88) µg/g and Kaduna 0.62-21.52 (12.36) µg/g. In 1985 the values of hydrocarbon levels recorded in the sediment samples were as follows: Lagos and Lekki lagoons 0.20-10.30 (4.20) µg/g; Niger Delta 0.05-44.06 (6.64) µg/g; Utorogu (Jan-Feb.) ND-9.41 (2.98) µg/g; Utorogu (June-July) 0.03- 68.06 (21.66) µg/g; Kaduna 2.91-5.00 (3.96) µg/g and Ibadan 8.09-27.79 (17.94) µg/g. The Lagos lagoon sediment samples monitored from January to December 1985 gave ND-2766.27 (11.13) µg/g. The results of this work showed that Lagos lagoon was more polluted than the Niger Delta in terms of petroleum hydrocarbons. Highest values of petroleum hydrocarbons were recorded close to oil activity points such as Ogharife field effluent canal, Chanomi creek at Egwa field, Orughene creek, in the Niger Delta area; or near human settlements such as Obotebe and Bakana or in an industrial area like Lever Brother's discharge point and Berger/National Oil/Ijora in Lagos. The results of Utorogu oil spillage gave a picture of the impact of oil in the aquatic environment. During the first sampling trip which took place within four months after the oil incident, aquatic lives (plants and animals) were seriously affected in the Utorogu swamp, but before the end of the study period (June 1985) the swamp had recovered and was bubbling with life again. Oil pollution indicator parameters such as the Carbon Preference Index (CPI), Pristane: Phytane ratio (Pr/Ph); Presence of Phytane, and Unresolved Complex Mixture (UCM) and the Marine Oil Pollution Index (MOPI) indicated that some of the stations were polluted by oil while most of the points studied in both Lagos and the Niger Delta were contaminated with petroleum hydrocarbons which may be from crude oil, refined oil or both. Moreover, all the contaminated and polluted samples showed petroleum hydrocarbon at different stages of weathering as reflected in their carbon range, the Pristane: n-C(17); Phytane:n-C(18) and UCM: n-alkane ratios.
A SEMI-EMPIRICAL SELF-CONSISTENT FIELD MOLECULAR ORBITAL (SCF-MO) STUDY OF THE GROUND STATE PROPERTIES OF SUBSTITUTED NAPHTHALENE COMPOUNDS
(1990-03) ADEKUNLE, A. O.
The ground and excited state properties of naphthalene and some of its derivatives have been studied. The molecular orbitals were evaluated using the modified Huckel Molecular Orbital (HMO) theory and the calculated molecular properties such as dipole moments, electronic transition frequencies, have been compared with experimental values. The electronic absorption spectra of some of the compounds were further studied in detail as to their band systems and characteristics, solvent polarity effects and hydrogen bonding effects. The dipole moment changes from ground to excited states were generally determined to be high. A linear regression analysis obtained for plots of the 'L(b) band maxima (υ(obs) versus solvent physical properties and solvent empirical parameters has shown that there is no meaningful correlation between solvent dielectric constant (ɛ) and solvent induced shifts. The oscillator strengths have been found to be generally low for the examined compounds in all the solvents. However, the electronic relaxation times calculated for each of the compounds give strong indication as to the likelihood of the band systems arising from mixed states. The relationship between relaxation times, t, and solvent viscosities,ᶯ, allows the prediction of large changes in spherical symmetries of the two band systems ('La and ’Lb) in both 1-naphthylamine and 4-nitro-l-naphthylamine. A possible existence of free internal rotation in the excited states of these molecules, has thus been suggested. The infrared spectra have been studied in the solid state and in solution and the vibrational frequencies assigned by making correlations with spectra of substituted benzene compounds and other related compounds. The substituent modes for each of the compounds have been discussed in detail.
EFFECT OF ELECTROSTATICALLY LINKED IONIZABLE GROUPS ON SULPHYDRYL REACTIVITIES OF HEMOGLOBINS
(1990-03) ABOLUWOYE, C. O.
The kinetics of the reactions of two sulphydryl reagents with the CysF9(93)β sulphydryl group of various human and animal hemoglobin derivatives have been studied as a function of pH at 20°C, at an ionic strength of 0.05 M. A quantitative analysis of the data was possible only for the 2,2'-dithiobispyridine data. For the 5,5'-dithiobis[2-nitrobenzoic acid] data, the equation relating the apparent second order rate constant to the model parameters was complex and therefore not useful for quantitative analysis. However, interesting results were observed for the 5,5'-dithiobis [2-nitrobenzoic acid]reaction. As a general conclusion, it is suggested that the reactivity of the CysF9(93)β sulphydryl , depends on two factors: the conformation of the sulphydryl group and the electrostatic effects of the charged ionizable groups on the protein. In order to determine the nature of the charged groups affecting sulphydryl reactivity, the reaction of hemoglobin with another sulphydryl reagent, was studied by potentiometric difference titration as a function of pH at 20°C and ionic strength O.05M. Differences were observed for various derivatives for the parameter Δh+ the number of protons released per sulphydryl group reacted. These differences reflect differences in tertiary structure between the derivatives studied rather than differences in quaternary structure.
SECONDARY METABOLITES FROM A LOCAL MEDICINAL PLANT - GARDENIA ERUBESCENS. STAPF. AND HUTCH
(1995-03) ADELAKUN, E. A.
A detailed Chemical analysis of the stem of Gardenia erubescens Stapf. & Hutch. was carried out. The crushed stem was sequentially extracted with petroleum ether, ethyl acetate and methanol. Subsequently the Petroleum ether, ethyl acetate and methanol extracts when subjected to phytochemical tests revealed the presence of steroids, flavonoids and saponins, while anthraquinones and alkaloids were not detected. The petroleum ether extract and the n-butanol soluble fraction of the methanol extract were further subjected to chromatographic analyses using a combination of column, TLC and preparative TLC. The TLC analysis of petroleum ether extract showed the presence of steroids and flavonoids as the major components. TLC analysis of the n-butanol soluble fraction of methanol extract however revealed only the presence of saponins. Purification of the petroleum ether extract on column of silica gel afforded, after further purification by preparative TLC, five known compounds, one fraction containing isomerie mixture of two compounds and one new bisnortriterpenoid compound. From the saponin fraction of the n- butanol soluble fraction of methanol extract, five compounds were isolated and identified. Four of these compounds were known while one was a new_ oleanene-type compound. A total of fourteen compounds were isolated and identified from both the petroleum ether extract and n-butanol soluble fraction of the methanol extract of the stems of Gardenia ernbescens. Characterization of the known compounds was achieved through spectral correlation with authentic samples and/or derivatisation and comparison of melting points with the known compounds. Full characterization of the new compounds was accomplished by use of 2D nmr experiments - COSY and 1H-13C nmr correlation spectra, assisted by NOE difference spectroscopy. The known compounds isolated and identified from Gardenia ernbescens in this work were: •D-Mannitol •Stigmasterol •Stigmasterol-3β-D-glucopyranoside •5-Hydroxy-7,4'-dimethoxyflavanone •5-Hydroxy-7,4'-dimethoxyflavone •5-Hydroxy-7,3',4'-trimethoxyflavanone •3β-Acetoxyolean-12en-30-oic acid •Isomerie mixture of oleanolic and ursolic acids •3β,23-Dihydroxyolean-12-en-28-oic acid •2β,3β -Dihydroxyolean-12-en-28-oic acid •2β,3β,23-Trihydroxyolean-12-en-2 8-oic acid and the two novel compounds were: •Erubescenone and •3β,23,24-Trihydroxyolean-12-en-28-oic acid.
Heavy metal concentrations in soils and accumulation in plants growing in a deserted slag dumpsite in Nigeria
(2008) Ogundiran, M.B; Osibanjo, O.
Early detection and remediation of heavy metals in soil and vegetation will ameliorate serious threats posed to human existence. An auto battery manufacturing company dumped slag containing proportion of heavy metals in an hectare of land at Lalupon, Ibadan, Nigeria. The extent of contamination of soil by heavy metals and their accumulation in plants around the abandoned slag was studied. Plants and the surrounding soils were sampled from different directions at increasing distance from the vicinity of the waste pile and their concentrations of heavy metals were determined. The levels of Pb, Zn and Ni in mg/kg ranged from 34.8 – 41500, 16.3 – 849 and ND – 48.2; 9.2 – 9700, 16.0 – 271 and 2.83 – 36.9; 4.5- 5670, 8.00 – 174 and ND – 322 in soil, plant root and plant shoot, respectively. The plant samples from the immediate environment of the waste were highly contaminated with Pb. Six plant species, particularly Sporobolus pyramidalis, met some of the conditions to be classified as hyperaccumulators for Pb, Ni and Zn, and three other plants fulfilled the criteria for heavy metal excluders. We conclude that the potential hyperaccumulators and excluders, under controlled conditions, can be used for phytoremediation of the site.
Mobility and speciation of heavy metals in soils impacted by hazardous waste
(2009) Ogundiran, M.B; Osibanjo, O.
This study describes the mobility and chemical fractionation of heavy metals (HMs) from a site impacted by auto battery slag that was generated from secondary lead smelting operations. Samples were collected from the waste pile and from the immediate surrounding soil at four depths to assess the migration and potential bioavailability of Pb, Cd, Cr, Ni and Zn. Total levels of the HMs and their fractionation were determined. The results indicate that highest levels of HMs are present in the uppermost layer with significant migration down the depth, thereby posing a threat to groundwater quality. In the fractions, the concentrations of the metals follow this sequence: Pb4Zn4Cd4Cr4Ni. The chemical fractions of Pb, Cd, Cr, Ni and Zn in the samples, expressed as mean concentrations of the sum of the individual chemical fractions, demonstrate that the HMs exist mainly in the non-residual fractions. For instance, the percentage of non-residual fractions of lead in the waste pile and the surrounding soil ranged from 48.9 to 95.6% and 69.4 to 98.3% respectively. The mobility factors of the heavy metals are significantly high indicating high potential mobility and bioavailable forms [IS1]of these HMs. The high concentrations of the HMs particularly Pb in the non-residual fractions, as observed in this study, shows the impact of anthropogenic activities on enrichment of natural soil with bioavailable HMs. Consequently, there is a need to be cautious in the way waste that is generated from heavy metals projects is added to natural soil.
Effects of phosphate chemicals treatments on auto battery waste contaminated soil in Nigeria
(2009) Ogundiran, M.B; Osibanjo, O.
Auto battery waste contaminated site poses potential threats to the environment and biological life through lead toxicity, thus making remediation imperative. The possibility of using phosphate chemicals to reclaim a grossly lead-contaminated site was explored. The study site was an abandoned lead-acid battery waste dumpsite in Nigeria. Phosphate chemicals were applied at 5 and 10% phosphorus levels to the contaminated soil collected from the site in incubation experiments. The air-dried sub-samples of the incubated soils were analyzed for pH, P, bioavailable Pb and TCLP- extractable Pb. Results showed that 99.5% of the applied phosphorus was removed by the end of the first week of incubation. Incubation time showed less effect on Pb immobilization. A 10% phosphorus application resulted in reductions of water soluble Pb between 77.8% and 86.4% thus eliminating to a reasonable extent, the hazard to living things and the environment. TCLP extractable Pb was reduced from 50.2 mg/L in untreated soil to below the acceptable value of 5.0 mg/L. An application of 10% CHP produced overall effectiveness in the reduction of bioavailable Pb, TCLP-extractable soil Pb. This treatment also had little effect on soil acidification and resulted in the least residual P. Results therefore indicated that phosphorus can be used as potential chemical remediation for cleanup of battery waste contaminated soils.
Medical Waste Management Practices in Nigeria, the Case of Lagos and Ibadan
(2011) Ogundiran, M.B; Oketola, A.A; Adefolu, O.R.; Mojeed, O.A.; Itiveh, S.E
Most developing countries are facing serious challenges on medical waste (MW) management. The current management practices of medical waste in Nigeria was studied using Lagos and Ibadan, an emerging mega city and the largest city in West Africa as case study. Sources of data were through questionnaire administration, waste sorting and characterization as well as sampling and analysis. The study revealed that there is no proper segregation of MW in most health care facilities studied. Over 75% of the MW handlers in Lagos and 98% in Ibadan are unaware of any policy and legislation regarding the management of MW. About 60% and 99%, respectively had no form of training in MW management and as such, are greatly exposed to different health risk. Furthermore, the States Waste Management Authority has no separate and appropriate dumpsites and landfills for disposal. The current system of MW management in Nigeria is in dire need of immediate attention and improvement. It is essential to develop a national policy on MW management and implementation of the existing ones to provide environmentally sound management measures to improve MW management in the country.
Evaluation of heavy metals bioaccumulation potentials of plants grown on waste contaminated soils.
(2011) Ogundiran, M.B; Osibanjo, O.
Determination of metal content and an assessment of potential use of waste cashew nut ash (CNAS) as a source for potash production.
(2011) Ogundiran, M.B; ||Babayemi, J.O; Nzeribe, C.G C.G
The potential use of waste cashew nut shell (CNS) ash as a source for potash production was investigated in this study. Managing waste ash generated from cashew nut processing is a major challenge, as land filling and open dumping of the waste ashes have been the main options in management of the ash in Nigeria. Economically viable ways of using waste ash rather than having to dispose of it have to be investigated. The CNS was air-dried for 4 weeks and combusted to ashes; the resulting ash was extracted with water for its potash content. Some parameters of the CNS, including moisture, dry matter, and ash content, were determined. Potash yield obtained was 33.4% of 150 g CNS ash used; analysis of the potash gave it a percentage purity of 78%, while purity on recrystalization increased to 86%. Potash yield from CNS ash was comparable to those reported for wood ash, plantain peels, and other agro-wastes. Also, the results showed that the CNS shared similar lignocellulosic properties and characteristics with hardwood biomass
Application of waste cashew nut shell ash showed significant reduction in mobility of Pb and Cd in waste battery contaminated soil
(2011) Ogundiran, M.B; Babayemi, J.O.; Nzeribe, C.G.
Increases in ore mining, metal smelting activities, and several other industrial practices in recent times have brought about contamination of soils at higher levels; these have prompted concerns on the consequent effects on the local and global ecosystem. Various remediation technologies have often been sought to meet the challenges. This study therefore seeks to assess the potential of cashew nut shell (CNS) ash for immobilizing Cd and Pb in battery contaminated soil. The ash samples used for the study were obtained from a waste cashew nut shell burning site, Olowopokun, Iseyin L.G.A of Oyo State, Nigeria. Some soil samples and sediments from a nearby stream at this site were taken. Soil samples were also taken from battery-contaminated dumpsites at Ile-Igbon, Lalupon, Oke-Omi, and Ikumapayi, in Lagelu L.G.A of Oyo State. One gram each of ground soil samples, ash and sediment were analyzed for heavy metals contents. Ash generated from waste cashew nut shell from cashew nut processing company dumpsite were mixed with contaminated soil samples from the lead battery dumpsite at ratios 10:1.5 and 10:3.0. The amended and un-amended soil samples were subjected to TCLP in accordance with US Environmental Protection Agency (USEPA) Method 1311. Cd gave 97% efficiency in the reduction of its mobility in the amended soil while Pb gave 80% efficiency. Increase in the quantity of CNS ash used for amendment from ratio 10:1 to 10:2 caused a rise in the pH of the soil, this translated to further reduction of the leached Pb and Cd from the soil. The assessment of the mobility of Pb and Cd in the soil as induced by the addition of CNS ash showed that there was reduction in the mobility of Pb and Cd from the contaminated soil samples as assessed by TCLP procedure. The use of the CNS ash in stabilizing the contaminated soil served as an effective waste disposal method for waste CNS as well as source for remediation of contaminated soil. Waste CNS ash could be a great source for in-situ remediation of contaminated soil.
KINETIC AND EQUILIBRIUM STUDIES OF THE REACTION OF 5,5'-DITHIOBIS(2-NITROBENZOATE) WITH HAEMOGLOBINS OF DOG AND DONKEY
(2012-06) ATOLAIYE, B. O.
The CysF9[93]β sulphydryl group is an indicator for tertiary and quaternary structure change in haemoglobin. Allosteric effectors such as proton and inositol hexakisphosphate (inositol-P6) influence its reactivity. This work was undertaken to study the effects of inositol-P6 and pH on the kinetics and equilibrium of the reaction of CysF9[93]β of dog (Canis familiaris) and donkey (Equus asinus) haemoglobins with 5,5'-dithiobis(2-nitrobenzoate) (DTNB). The number of sulphydryl groups in haemoglobin was determined by titrations with p-hydroxymercury(II)benzoate (pMB) and DTNB. The pseudo-first order kinetics of the reaction of haemoglobin with DTNB were studied at 25oC, with and without inositol-P6. Values of observed rate constant (kobs) were plotted against [DTNB] to obtain the apparent second order forward rate constant, kF. Equilibrium studies of the DTNB reaction were carried out at 25°C, with and without inositol-P6. An equation was derived for the determination of the equilibrium constant of the reaction, Kequ, within a series of equilibria. Kinetics and equilibrium experiments were carried out on the oxy, carbonmonoxy and aquomet derivatives of the haemoglobins in the pH range 5.6 to 9.0. The number of sulphydryl groups in dog haemoglobin reacting with DTNB and pMB were 2 and 4 per tetramer respectively, while those of donkey haemoglobin gave two sulphydryl groups per haemoglobin tetramer for both reagents. The plot of kobs against [DTNB] was linear at each pH, with a non-negligible positive intercept, indicating that the reaction of CysF9[93]β of dog and donkey haemoglobins with DTNB is a reversible process. The slope of each plot (kF) varied with pH, giving different profiles for the three haemoglobin derivatives. Inositol-P6 had a significant effect on kF for the two haemoglobins. The Kequ showed strong pH dependences for all derivatives of the two haemoglobins. Inositol-P6 had only a minor effect on the affinity of dog haemoglobin for DTNB. By contrast, it increased the affinity of donkey haemoglobin by two orders of magnitude. These results could not be accounted for by changes in the tertiary conformation transition constant, Krt caused by inositol-P6. Inositol-P6 had little effect on Krt in the case of dog haemoglobin: Krt for stripped dog haemoglobin was calculated as 0.75 ± 0.13; in the presence of inositol-P6 Krt became 0.70 ± 0.20. Krt for stripped donkey haemoglobin increased from 0.46 ± 0.02 to 0.83 ± 0.20 in the presence of inositol-P6. This indicated that changes in tertiary structure govern the affinity of haemoglobin for DTNB.
SPATIAL AND TEMPORAL VARIATIONS OF PHYSICOCHEMICAL CHARACTERISTICS OF SURFACE WATER AND SEDIMENT OF OSUN RIVER IN SOUTHWESTERN NIGERIA
(2012-09) ABIDEMI, OLAYIWOLA, OLAJUMOKE
Osun River is important for domestic, recreational and other activities. It flows along a channel that may be polluted by inputs from industrial, agricultural and other anthropogenic activities thereby limiting its normal use for drinking, fishing, recreation and other purposes. Available literature on the river quality is limited in scope, frequency of sampling and duration of studies. Therefore, a study of the river and its tributaries was carried out to determine the spatial and temporal variations of physicochemical characteristics of its water and sediment. Surface water and sediments were sampled bimonthly from July 2006 to May 2008 at upstream and downstream points of the main river course and 31 tributaries. Sampling was by compositing at each point of 90 locations for surface water and 63 identified locations for sediment, where possible. Water samples were analysed for alkalinity, hardness, ammonia, anions, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), heavy metals and turbidity. Sediment samples were analysed for organic carbon, particle size and selected heavy metals using APHA methods. Location-based and overall data obtained were fitted into a time series model using a number cruncher statistical system, and applied to predict contaminant concentrations up to year 2018. The Pratti model was applied to determine locational pollution classes (Class 1-5) based on gross organic pollutants and ammonia. Statistical evaluation of data involved use of principal component analysis, analysis of variance and Student’s t-test at p = 0.05. The concentrations (mg/L) of alkalinity, hardness, ammonia, nitrate, phosphate and chloride were 93±130, 116±120, 4.2±6.6, 1.8±1.5, 0.15±0.23 and 54±110 respectively. Those of DO, BOD, COD, lead, copper, cadmium and zinc were 7.9±3.0, 6.9±7.5, 135±120, 0.003±0.004, 0.003±0.004, 0.002±0.003, 0.07±0.10 mg/L respectively and turbidity, 34±43 FTU. Values of parameters for upstream locations did not differ significantly from downstream points, indicating randomness of contaminant inputs. Turbidity, sulphate and DO were higher during the wet seasons while phosphate, nitrate and BOD were higher in the dry seasons. Metal levels correlated positively between water and sediment, with coefficients ranging between 0.75 for Cu and 0.99 for Co. Highest concentration factors in sediment were 233 (Pb) and 171 (Zn). Inter-element association in sediment was high only for Pb/Cu (r =+0.72). Two locations fitted into Class 4 (grossly polluted) of the Pratti scale, while thirty-one were Class 3 (slightly polluted) which was UNIVERSITY OF IBADAN LIBRARY iv indicative of pollution derived from mild industrial and agricultural impacts. Fifty-three locations were acceptable (Class 2), and four excellent (Class 1). Time series modelling fitted well for nitrate (R2= 0.79), phosphate (R2= 0.84) and BOD (R2= 0.71) data and gave their 2018 predicted values of 19.2, 18.1 and 21.9 mg/L respectively. Comparison with WHO guidelines indicated that 37.0% of sampling points for surface water were unfit for drinking mostly due to high turbidities, but suitable for irrigation. Metal levels in sediment were within international limits. Osun River and its tributaries have been adversely impacted upon by non-point pollutant inputs. Further deterioration in the near future was predicted, and heavy metal pollution is not yet a significant problem in the river basin. Keywords: Osun River, Gross organic pollution, Modelling, Spatial variation, Water quality. Word count: 500
HEAVY METAL BURDEN OF SOILS AND THEIR ACCUMULATION POTENTIALS IN SOME FOOD CROPS OF SELECTED FARMS IN KOGI STATE, NIGERIA
(2014-03) EMUROTU, Jude Ehwevwerhere
Heavy metal contamination in soil may be reflected in food crops due to plant uptake and such crops when consumed may cause adverse health effects. The assessment of toxic metal burden of soils and the capacity of food crops to accumulate these metals are essential. Such studies have not been reported in literature for Kogi State, a state noted for intense agricultural activity. The aim of this study was to determine heavy metals in soils, food crops, irrigation waters and sediments of dam of selected farms in Kogi State and also metals uptake potentials and toxicity threshold limits in crops. Soils and plants from nine major farms, three from each senatorial district, and a control site (another farm), were randomly sampled quarterly from May, 2007 to February, 2009. Thirty-two soil samples were obtained from 0-15 and 15-30 cm depths in each farm and control site, to make 320 composite samples. A total of 640 plants samples (leaves and edible parts each of pumpkin 64, passion fruit 96, maize grain 96, sugar cane stem 64 and tubers of cassava 320) were collected. Fifty-six samples of each of irrigation waters and sediments were collected. Soils, water and sediments were each digested with HNO3 while 3:1 HNO3:HClO4 was used to digest the crops. Digests were analysed for Cd, Co, Cu, Ni, Pb and Zn by atomic absorption spectrophotometry. Speciation of metals in soil was done by Tessier sequential extraction procedure and soil-plant transfer factor was determined as the ratio of metal concentration in plants to soil. A soil-plant equilibrium model (STRATA) was used to analyse soil-plant metal data in order to obtain crop uptake characteristics and toxicity threshold limits. Data were analysed using ANOVA at p = 0.05. The mean concentrations of Cd, Co, Cu, Ni, Pb and Zn in top soils were 0.6±0.7, 5.4±3.9, 4.3±2.3, 15.7±9.2, 11.8±6.1 and 26.0±17.0 mg/kg respectively, while subsoil values were 0.7±0.7, 5.0±3.3, 3.9±2.1, 14.6±8.3, 11.7±5.4 and 25.0±14.0 mg/kg respectively. These did not vary significantly among farms. Proportions in non-residual soil phases were 82.6% Cd, 48.6% Co, 72.5% Cu, 73.2% Ni, 41.9% Pb, and 84.3% Zn. Mean concentrations (mg/kg) in edible crop parts were: Cd 0.5±0.1, Co 4.4±3.0, Cu 4.4±0.2, Ni 25.5±9.2, Pb 0.2±0.1 and Zn 20.1±1.3. Nickel levels in cassava tubers and leaves iv (34.5±19.0 and 29.0±16.0 mg/kg respectively) were significantly higher than in the control (3.1±0.5 mg/kg) and exceeded Chinese standard limit of 10 mg/kg. Metals levels in water and sediments were within standard limits of 0.001-3.0 and 6.0-25.0 (mg/kg) respectively. Soil-plant transfer factors indicated low accumulation into crops. Transfer factors for Cd, Co, Cu, Ni, Pb and Zn in maize grain were: 0.4, 0.01, 0.6, 1.9, 0.02, and 1.2 respectively, and in tubers were: 0.4, 0.01, 1.8, 2.5, 0.01 and 0.7 accordingly. Metal concentrations in crops parts were generally lower than model-derived threshold limits for toxicity in plants. There was no heavy metal contamination in investigated food crops except nickel in cassava. Therefore, the soil may not require any form of remedial action. Keywords: Heavy metals in food crops, Soil and sediment contamination, Metal uptake, Metal speciation, Toxicity in plant. Word count: 497