Chemistry

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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.
AN X-RAY CRYSTALLOGRAPHIC STUDY OF SOME WOOD EXTRACTIVES
(1967-02) ADEOYE, S. A.
EXTRACTIVES FROM KHAYA SPECIES
(1968-03) ADESOGAN, E. K.
The chemistry of ß-furan-containing extractives obtained from trees of the family Meliaceae (and one tree from the family Rutaceae) is briefly reviewed and their biogenesis is discussed. In continuation of our study of the extractives from the family Meliaceae in this department, five species of the genus Khaya have been examined. The seed, timber, bark, root, and root-bark of three species, K. senegalensis, K. ivorensis, and K. grandifoliola, and the seeds of the two others, K. anthotheca, and K. nyasica were examined. The extracts are mainly the tetranortriterpenes with a ß-substituted furan, and about thirty of these were isolated and structures were assigned to nearly all of them. The known ones include khivorin, 7-deacetoxy-7-oxo-khivorin, 7-cleacetoxy-7-oxogedunin, methyl angolensate, mexicanolide, and deacetylgedunin. Those characterised and reported for the first time include khayasin, 6-deoxy-3ß-tigloyloxyswietenolide, 6-deoxy-3ß-benzoyloxyswietenolide, khayanthone, 3-deacetylkhivorin, 3-deacetyl-7-deacetoxy-7-oxokhivorin, methyl 6-hydroxyangolensate, grandifoliolin, 3-destigloyl-6-deoxyswietenine, 3-destigloyl-6- deoxy-3ß-acetoxyswietenine, 3ß-dihydrocarapin, and 3-destigloyl-6- deoxy-3ß, 12ß-diacetoxyswietenine. Others prepared before, but isolated as natural products for the first time include deoxy- andirobin, and 6-deoxyswietenolide. In addition two substances, A and B from K. ivorensis root-bark have structures proposed for them which are still to be confirmed, while not much is known of the structures of a few others especially methyl senegalensate. Most of these extracts contain glycosides and steroids, ß-sitosterol in particular. Of these only the steroid hormone 20ß-acetoxy-3-oxopregn-4-ene, a new compound, was sufficiently studied to be assigned a structure which was confirmed. The structural elucidation of these compounds have depended almost entirely on their spectral properties including those of their Chemical transformation products. Obviously physical properties played a great part especially in confirming a known compound by comparison of data. The co-occurence of some of these compounds have strengthened the argument for the biogenesis proposed. The chemotaxonomic implication was also discussed. A number of interesting reactions including some rearrangements are discussed and mechanism for some of them have been suggested.
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.
STUDIES ON THE CHARACTERISTIC pH OF HAEMOGLOBINS
(1972-01) ADEOSUN, O. S.
The thermodynamics of the azide binding reactions of the hybrids of human and canine haemoglobins (i.e. α2Aβ2Ca and α2Caβ2A) as well as the isolated α and ß polypeptide chains of human and canine haemoglobins have been studied at various pH's and temperatures. Plots of -ΔH° against pH, for all the species, show a distinct maximum. The pH at which the maximum value of - ΔH° occurs is termed the 'characteristic pH' (pH ch). From the results it is concluded that the value of pH ch for the haemoglobin tetramer is an average of the pH ch's of the separate α and ß polypeptide chains although: the form of the curve of -ΔH° against pH is a function of the tetramer and cannot be obtained by averaging -ΔH° values for the individual chains. The Bohr effect of the two hybrids has also been measured and compared with that of the parent haemoglobins. A study of the equilibrium reaction between oxyhaemoglobin and carbonmonoxide was carried out and the accompanying thermodynamic data assessed in terms of the mechanisms postulated for explaining ligand binding reactions of methaemoglobin.
THE REACTIONS OF SOME ACTIVATED AROMATIC HALIDES WITH PIPERIDINS, AND N-BUTYLANINE IN DIPOLAR APROTIC AND DIPOLAR PROTIC SOLVENTS
(1975) ADENLE, M. A.
The reactions of 2-chloro-5-nitro pyridine with piperidine have been studied in acetone and in nethanol. In acetone, the rate constants are measured as a function of the anine concentration. In methanol, the Arrhenius parameters are obtained. In methanol, except for a very slight (almost negligible) downward trend of rate constants at very high concentration which is explained in terms of Charge - transfer complexes, there is no base catalysis and the observed rate constants are the rates of formation of the intermediate complex. The rates of reaction of 1-X-2, 4-dinitrobenzene (X=F, Cl) with piperidine and n-butylamine in methanol, acetone, and chloroform (stabilised and destabilised) have been measured as a function of the amine concentration. In acetone, the reactions of both substrates with piperidine show true base catalysis with K3/K2 > 50 in both cases. In Chloroform with n-butylamine, there is very little rate increase with increasing amine concentration. For both Substrates, K3/K2=3. This is explained in terms of hydrogen-bonding in the intermediate state. In methanol, the reaction of the chloro Substrate with piperidine gives a small linear increase of rate constants with increasing amine concentration; while for the fluoro substrate, the graph of rate constants against amine concentration gives a doubly sloped curve. This is due to some special unknown medium effects. In acetone, the reactions with n-butylamine give rather peculiar results. The chloro substrate appears to be more sensitive to catalysis by amine than the fluoro substrate - a Situation hitherto unknown. In general, for the reactions in methanol and Chloroform, there is not much base influence; while those in acetone are dependent on the base strength.
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.
AN INVESTIGATION OF SOME HORMONAL BASES FOR ABSCISSION IN COWPEA (VIGNA UNGUICULATA L. WALP.)
(1977-05) ADESOMOJU, A. A.
The Investigations carried out on the abscission problem in cowpea are reviewed. The Isolation 5 characterization 9 physiological roles, chemistry, biosynthesis and metabolism of the various groups of plant hormones are also reviewed. Using biological assays and combined gas-liquid chromatography- mass spectrometry (GC-MS, some of the hormones in the extensively purified acidic ethyl acetate extracts obtained from 2-day old and 6-day old cowpea fruits were examined. Biological assays indicated the presence of only Inhibitors in the 2-day old fruits but inhibitors as well as gibberellins and auxins were indicated to be present in the 6-day old fruits, GC-MS analysis of the extract from 2-day old fruits afforded the identification of the known inhibitors, abscisic acid and phaseic acid. 6’-hydroxymethyl abscisic acid was also identified in the extract and this is the first reported evidence that 6’-hydroxymethyl abscisic acid occurs naturally. Several plant hormones were identified (GC-MS analysis) in the extract from 6-day old fruits. These were abscisic acid, phaseic acid, dihydrophaseic acid,’1iso1dihydrophaseic acid, 6’-hydroxyinethy abscisic acid; gibberellins A4, A6, A8, ‘iso’ A8,and A20. Gibberellins A1,A5,and A29 were also believed to be probably present. Two components, believed to be two new gibberellins were also identified in the extract and were tentatively called gibberellins X and Y. Tentative structures were assigned to these two new gibberellins. Purified acidic ethyl acetate extract obtained from fruits that were over six days old was also analysed on the GC-MS. The result was essentially similar to that obtained for the extract from the 6-day old fruits. The crude acidic ethyl acetate extracts from 6-day old seeds and the fruit walls of the 6-day old fruits were also examined on the GC-MS. Several gibberellins were tentatively identified in the extract from the seeds but only one gibberellin could be identified in the extract from the fruit walls. The methyl esters of 16α-hydroxy, 17-hydroxy, and 16α, 17-dihydroxy derivatives of gibberellin A34 and the 16-epimers of the last two compounds were synthesized from gibberellin A4. This was done in order to correlate the structures that were tentatively assigned to the two new gibberellins with the natural compounds. The disparity in the hormonal contents of the 6-day old and 2-day old fruits is discussed in relation to the abscission problem in cowpea.
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.
DESULPHURIZATION OF NIGERIAN LAFIA COAL FOR METALLURGICAL COKE PREPARATION
(1988-01) ADERONPE, W. I. A.
The Government-owned integrated iron and steel plant under construction in Ajaokuta has been designed to operate through the blast-furnace process. The blast-furnace requires metallurgical coal. It therefore became necessary and relevant to the national economy to scientifically work on Nigerian coals with a view to using same as metallurgical coal. Lafia coal is the only Nigerian coal that produces coke lump after dry distillation (carbonization). The property of coke- ability therefore attracted attention towards Lafia coal. The main interest was to so prepare the coal that as much as possible of it will be usable for metallurgical coke preparation for use in Ajaokuta blast-furnace. Lafia coal was subjected to chemical characterization and petrological studies. It became clear that it was high in ash and sulphur. Silicates, pyrites and carbonates of various elements constituted the inorganic mineral inclusions. Analytical data gave the sulphur varieties in Lafia coal to be organic (0.1 - 0.7%), pyritic (1.4 - 4.4%) and sulphate (0.01 - 0.07%). Pyritic sulphur which predominates in Lafia coal can be removed by physical means. Chemical desulphurization which is reducto-oxidative type of chemical reaction impares coal cokeability. A plunge was thus made for physical desulphurization techniques to bring down the total sulphur in Lafia coal to the level that will make it acceptable as a metallurgical coal with regards to its sulphur content. Trace elements in Nigerian coal ash determined using the Atomic Absorption Spectrophotometer (AAS) and confirmed with the Inductively Coupled Plasma Emission Spectrophotometer (ICPES) showed that the relative abundance of the elements in the coals depended on the biogeo-chemistry of the area of the deposit as follows: Lafia coal; F>Zn>Mn»V Cr>Ni>Cu>B>Pb>Ca>Be>Mo>Cd>Hg Enugu coal; B>Mn>V F>Cr>Zn>Cu>Pb Ni>Co>Be>Mo>Hg Okaba coal; Mn»B»V>Cr>Cu>Pb>F=Ni>Zn Co>Be>Mo>Hg Trace element content of coal was considered in connection with the impact of coal utilization on the environment. From the study it was concluded that either the wet concentrating table or the froth flotation method could be used to substantially desulphurize Lafia coal to meet the requirement of metallurgical coal.
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.
METAL(II) TETRAFLUOROBORATE COMPLEXES OF SOME DICARBOXYLIC ACID HYDRAZIDES
(1990) ADENIYI, A. A.
Eighty-eight divalent metal complexes derived from dihydrazides of oxalic, malonic, succinic, adipic, phthalic and terephthalic acids, with manganese( 11), cobalt(ll), nickel(ll), copper(IJ), zinc(ll), cadmium(ll), mercury(ll) and magnesium tetrafluoroborates have been prepared. The effect of 1:1 and 1:2 metal to ligand reactant ratios have been examined. The complexes have been characterized on the basis of their analytical data, magnetic susceptibility, electronic and IR spectral studies as well as conductance measurements. Reactions involving 1:1 and 1:2 metal to ligand ratios gave complexes with different metal to ligand stoichiometry in most cases. It is evident, from the analytical data, that complexes precipitated out mostly with 1:2 and 1:3 metal to ligand stoichiometry. However, complexes of oxalic dihydrazide with Cu (II) and Hg (II), succinic dihydrazide with Co (II), Ni(ll), Zn(ll) and Mg prepared using a 1:1 molar reactant ratio contained one and a half moles of ligands. Similarly, complexes of Mn(ll), Ni(ll) and Hg(ll) prepared using a 1:2 molar ratio of metal salt to adipic dihydrazide contained one and a half moles of adipic dihydrazide. Nevertheless, reactions involving 1:1 and 1:2 molar reactant ratios gave the same set of compounds in phthalic dihydrazide with Co(ll), Ni(ll) and Zn(ll) tetrafluoroborates respectively. Likewise the complexes of adipic and malonic dihydrazides with Zn(BF4)2 .6H2O4 and Cd(BF4)2 .7H2O respectively. The complexes have poor solubilities in methanol, ethanol, acetone, nitrobenzene, nitromethane, benzene, hexane, aceto- nitrile, dimethylformamide, dimethylsulfoxide and water. But the complexes of inanganese( 11), cobalt(ll), zinc(ll) and cadmium(II) with oxalic, malonic, succinic and adipic dihydrazides were found to be soluble in water. Similarly, nickel(11), CO ppe-f (11) and magnesium complexes of malonic and succinic dihydrazides were soluble in water, so also is the complex of mercury(ll) with adipic dihydrazide. In addition, the complexes of succinic dihydrazide, with manganesef11) and cadmium(ll) tetrafluoroborates were soluble in dimethylsulfoxide. The infrared spectra indicate that the bonding sites in these compounds are the carbonyl oxygen and the amino or amide nitrogens. The electronic and magnetic data of the complexes of manganese( 11), cobalt(ll), nickel(ll) and copper(ll) at room temperature suggested that they assume octahedral geometry. Generally, for a given ligand, the 1:2 complex has a lower magnetic moment than the 1:3 complex. The Variation of the moments with chain length does not appear to be systematic at room temperature. However, the magnetic moments for the Zn (11), Cd(II), Hg(ll) and Mg indicates that they are diamagnetic with some evidence of polarization paramagnetism. The conductance data of the complexes that were soluble in water and dimethylsulfoxide revealed 1:2 type electrolytes.
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.
DEVELOPMENT OF RESIN-BOUND REAGENTS FOR ANALYSIS OF CARBOXYLIC ACIDS AND AMINES
(1993-12) ADEWUYI, G. O.
Resin-bound-reagents made up of ionically-bound 2- naphthalene-methanol and covalently bound and sodium-benzoxazole- 2-sulfonate have been synthesized and utilized as analytical reagents for the pre-chromatographic derivatization of fatty acids (i.e. acetic, lauric, capric, hexanoic, octanoic, nonanoic, palmitic, docosanoic linoleic), 1° and 2° aliphatic amines and amino acids respectively. The reagents have been designed to contain fluorescent moieties attached to the anionic and cationic resin backbones through sulfonated ester linkages. These moieties imparted UV and FL detector properties to the final derivatives. The derivatization reactions were performed before the thin- layer Chromatographie separations. Standards we,-e prepared and were used in monitoring the extent of reactions on the resin support. The derivatives were chromatographed and fluorescent spots were observed under UV light. These solid phase derivatizations have led to preliminary investigation of these two functionalities before embarking on instrumentation analysis such as high performance liquid chromatography with UV or fluorescence detection and HPLC-MS Identification.
PHYTOCHEMICAL AND PHARMACOLOGICAL EXAMINATION OF ENTANDROPHRAGMA ANGOLENSE AND CRYPTOLEPIS SANGUINOLENTA
(1994-03) KOLAWOLE, A. J.
Dried, pulverized stem bark and the root bark of Entandrophragma anqolense were separately extracted with methanol. The crude methanolic extract of the stem and root bark of E. anqolense were subjected to column fractionation and purification. This exercise afforded the Isolation of methyl angolensate, 2.26% yield from the stem bark and 0.27% yield from the root bark. The effect of the crude methanolic stem bark extract was investigated on indomethacin-induced gastric ulcer in rats. Its effect was dose-dependent, doses ranging from 0.4 to 1.6 gkg-1 body weight (BW) produced significant effect (P < 0.05). At the highest dose used (1.6gkg-1 BW), complete inhibition of ulceration occurred. Toxicity study showed that the extract was not toxic when doses ranging from 20-200gkg-1 BW was administered to experimental rats. It was established that methyl angolensate is the major anti- ulcer principle present in the methanolic extract of the stem bark of E. angolensate. Methyl angolensate produced a dose-related inhibition of gastric ulceration induced by indomethacin, 40mgkg BW being more effective than 40mgkg-1 BW of propanolol. 80mgkg-1 BW of methyl angolensate completely inhibited gastric ulceration. Methyl angolensate also significantly reduced gastric acid secretion induced by histamine and carbachol (1.0mgkg-1 BW). Thus we confirmed that methyl angolensate produces its anti-ulcer activity through inhibition of gastric acid secretion. The roots of Cryptolepis sanquinolenta were extracted with methanol. Column fractionation of the methanolic extract afforded the Isolation of a new benzocarboline alkaloid labelled (CS-1) melting point 272-274°C. Spectroscopic analysis of CS-1 including the infra-red (IR), 13 ultra-violet (UV), mass spectrum (MS), proton and C-nuclear magnetic spectroscopy were reported. This new alkaloid exhibited anti-microbial activity on five pathogenic organisms. The in-vivo anti-malarial study of the aqueous extract of the roots of sanguinolenta was done on Plasmodium yoeli nigeriensis in mice. Anti-malarial activity of the extract was determined by examining the blood schizontocidal action in established infection using chloroquine as Standard drug for comparison. The extract showed a dose-dependent effect against the malarial parasite.
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.