FACULTY OF SCIENCE

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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.
STUDIES IN THE THEORY OF MULTIPLIERS WITH APPLICATIONS TO SEMIGROUPS OF OPERATORS
(1974-08) ADEWOYE, T. O.
This thesis divides naturally into two parts. The first half is a study of the general theory of multipliers, while the second half deals with applications of the theory of multipliers to the theory of semigroups of operators defined on a Banach spice. We study the multiplier problem for an abstract Hilbert space li, and generalise to H certain important results established for La(G)-multipliers (Larsen [12], Hewitt and Ross [8]). A significant result of this study is the Identification of certain projection operators on L2(G) which are, in several respects. Like the translation operators on Ls (G). We also discuss the restricted multiplier problem for the Banach algebra L1(G) of all absolutely integrable complex-valued functions defined on a compact group G, and we obtain results which are analogous to those obtained by Brainerd and Edwards [1] for L1 (G), where G is a locally compact abelian group. In connection with, semigroups of operators, we discuss, in the context of various Banach spaces, the representation of the multipliers which arise semigroups of operators on these Banach spaces. In this respect, we extend the results of Hille and Phillips [10] proved for the circle group (and generalised to compact abelian groups by Olubummo A. and Babalola V.A. [13]) to certain Banach spaces which are not even function spaces. All these results put together provide a good link between the theory of multipliers for a Banach space and the theory of semigroups of operators on the Banach space.
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.
A GRAVITY PROFILE OF THE LOWER BENUE TROUGH OF NIGERIA
(1976-06) ADIGHIJE, C. I.
Gravity measurements were made along a roughly east-west profile across the lower Benue trough, with the main objectives of investigating the nature and configuration of the basement beneath the trough and determining the thickness of the sedimentary cover rocks. I87 gravity stations were established at 2-4km intervals and standard corrections were applied to the observed gravity values. A Bouguer gravity map of the whole Benue trough is compiled from the results of these measurements and data obtained from previous works. The map shows that the positive anomaly along the axis of the trough is a most prominent regional feature that extends over the whole length of the trough. The abrupt truncation of the positive anomalies along a NNE-SSE line may represent the Cretaceous continental margin. The axial positive is ascribed to the doming of the basement underlying relatively dense Albian Shales and their associated intermediate to basic intrusives along the trough axis as a result of tectonic processes. "Growth” of the positive anomaly towards the South is attributed to the basement being at a shallower depth in the lower Benue than in the upper Benue trough and to the probability that oceanic crust underlies the sediments at the southwestern end of the trough. The negative anomalies are due to thick sedimentary sequences which fill the flanks of the trough. The sediments are estimated to have a maximum thickness of 4.25km in the surveyed area of the lower Benue trough.
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.
SOME ASPECTS OF THE ATMOSPHERIC ELECTRIC CLIMATE AT IBADAN
(1980-07) ADEWOLU, D. O.
The diurnal variations of the atmospheric electric Parameters and meteorological Parameters for the harmattan season of November 1978 to March 1979 are presented. The percentage variations of temperature are mirror images of those of vapour pressure which show pronounced depressions around noon when the little available moisture in the air near the ground is distributed over greater and greater heights by convection. The diurnal patterns of dust concentration, measured for the first time in this locality, is single periodic with minimum between 0400 hrs and 0800 hrs L.T. and maximum around 20 hrs L.T. This pattern is closely related to that of windspeed, and is explained in terms of the copious amount of dust transported southwards from the Sahara desert. The diurnal curves of the electric elements. I, H and p show pronounced “austausch” depressions around noon and marked peaks at 08.00 hrs which are attributable to the sunrise effect. An average value of the total nuclei concentration during the Harmattan months is computed to be about 2.8x10(10) particles per m(3) for this Station. This value is based on the measurements of the polar conductivities made for the first time in Ibadan.
BIOSYSTEMATIC STUDIES IN SOME NIGERIAN SPECIES OF ANTHERICUM LIN. AND CHLOROPHYTUM KER-GAWL. (LILIACEAE)
(1981-03) ADEYEMI, F. A.
Field surveys and investigations of representatives of Anthericum L. and Chiprophytum Ker-Gawl. complex in Nigeria were carried out in their natural habitats in at least sixteen States of the Nigerian Federation. All herbarium specimens in the Forestry Research Institute, Ibadan and in nine Nigerian Univetfsities visited were examined (if any). So far, ten species of Anthericum and fifteen species of Chlorophytum have been reported and collected in Nigeria. They were all studied morphologically. Detailed ecological analyses including the Chemical composition of their soils were carried out on three taxa of Anthericum and ten taxa of Chrolophytum. Many living populations were sampled from their different natural habitats in Nigeria, Their representatives were cultivated in three locations for experimental studies. Data were collected on the morphology by conventional methods and analysed. Anatomical data were amassed from the leaf surface patterns and the roots. Types of leaf margin anatomy were noted. Cytological studies were carried out in five taxa of Anthericum and eleven taxa of Chlorophytum. There were inter-generic hybridization tests. The use of lea f vein spacing interval and anther: filament ratio as taxonomic criteria have been suggested and their usefulness in the monocotyledon taxonomy, especially in Liliaceae, needed to be further explored. The importance of leaf margin anatomy as a taxonomic criterion above species level was highlighted. Chromosome counts for seven taxa were confirmed, viz; C. macrophvllum (A. Rieh.) Aschers 2n = 28. C. blepharophvllum gchwinf. ex Bak. 2n = 28. C. atenopetalum I Bak. 2n = 14. C. atenopetalum II (sp. nov.) 2n = 14. C. laxum R. Br. 2n = 14. C. inomatum Ker-Gawl. 2n = 14. C. togoense Engl. 2n = 14. New chromosome counts were recorded in :- C. geophilum Peter ex. v. Poelln. 2n = 28. C. alisaifolium Bak. 2n = 16. Chiprophytum X ( related to C. elatum ) 2n = 16. C . caulescens (Bak.) Marais & Reilly ( formerly A. caulescens Bak.) 2n = 16. A. Limosum Bak. 2n = 16. A. pterooaulon I Welw. ex Bak 2n = 24. A. Pterocaulon II 2n = 16. A. nubicum Bak. 2n = 16. A. pubirhachis Bak. 2n = 16. A. uvuiense 2n = 16. The possible evolution o f chromosome numbers in the complex has been postulated. The possible chromosome evolution o f the complex based on the available data from this work and existing literature has been proposed. Evidence was adduced to Support the Suggestion that the possible basic Chromosome number in the complex was x = 4, and that n = 8 Was a secondary basic number. It has also been contended that n =7 and n= 6 evolved from a more primitive n = 8. Supplementary evidence in Support of Marais and Reilly’ s (1978) transfer of A. caulescens from Anthericum into Chloronhytum as C. caulescens was adduced. A form of C.stenopetalum has been elevated to species level on account of its morphological, cytological and genetic differences. A new taxonomic key has been proposed for the Separation of Anthericum and Chiprophytum. The possible mode of evolution of some Nigerian species of Anthericum and Chlorophytum. based mainly on their leaf surface patterns, has been proposed.
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.
INITIAL STAGES AND SOME CHARACTERISTICS OF WEST AFRICAN LINE SQUALLS
(1983-03) ADEDOYIN, J. A.
A review of West African synoptic weather pattern reveals that the sub-region experiences a special kind of atmospheric disturbance -the line squall - whenever the south-westerlies cover, approximately, the whole of Nigeria. Various methods that have been used to study the squalls (i.e. observational investigations, satellite investigations and modelling) have not been very successful in isolating the trigger mechanism of the phenomenon. It is been proposed that line squalls are initiated through the amplification (with time) of any wave-like perturbation along the surface of discontinuity between the south-westerlies and the north-easterlies. The amplifying perturbations could block the 650 mb. mid-tropospheric jet which further distorts the 'bump' formed by the undulating perturbation. This distortion forces the southwesterlies further up and they could condense. The precipitates fall into the underlying, dry jet and some of them evaporate; the latent heat of evaporation being supplied by the jet. The jet, now cooler, sinks. On sinking, the jet could hit the surface of the earth on which it forms the squall front and crawls; thereby lifting the south-westerlies ahead of it. The cycle of condensation, evaporation and sinking then continunes. A gravity-wave model of this mechanism is presented through the solution of a frequency equation with the aid of a two-layer atmospheric model. The solution is an eigenvalue problem from which many modes of different growth rates and phase velocities could be obtained. Some of these phase velocities will be complex - the real part representing the phase velocity while the imaginary part represents the amplification. Waves with the largest amplifications (i.e. the largest imaginary part) are those that could possibly block the 650 mb. mid-tropospheric jet and trigger off line squalls. Among others, this proposal on the trigger mechanism of line squalls is able to explain: (i) the preference of highlands as places of origin of line squalls, (ii) the close association between the speeds of propagation of line squalls and the mid-tropospheric jet and (iii) the observed overturning of the atmosphere after the passage of line squalls.
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.
An evaluation of the prevalence and intensity of liver fluke infection in cattle slaughtered in Jos abattoir with comments on the incidence of amphistome infection
(1986) Okwuosu, V. N.; Ariyo, S. A.
An evaluation of the prevalence of liver fluke disease of cattle revealed an upward trend for an urban abattoir. A total of 3072 animal gall bladders were assayed between December 1980 and January 1982 and 74.06 + 6.46% were positive, the major fluke species were Fasciola gigantic and diocrocoellum hospes with a few case of schistosoma bovis. The max/min. monthly prevalence rates were 85.42% and 60.00% respectively. The mean rates for D. hospes and F. gigantic were 57.95 + 6.58% nd 48.71 + 11.66% respectively. T-test assessments showed these mean to be significantly different. The study further showed that for natural infections of cattle mixed infections were more frequent than singe infections. The mean value were 32.13% as against X single infection rates of 25.5% and 16.45% for D. hospes and F. gigantic. Chi-square analysis confirmed that mixed infection rates were significantly higher than single infections for both species. The flike species were highly prolific, producing mac egg count of 50 x 103 and 60 x 103 c.p.ml for F. gigantic and D. hospes respectively. There was variation in egg count due to seasons with significantly more eggs produced in the dry than in the wet season, for freely infected animals, there wa suppression of egg production in mixed infections which though affecting the species, had more effect on F gigantic, this resulted in significantly more eggs being produces by either species in single than in mixed infections
MICROBIOLOGICAL STUDIES OF GUINEA CORN FERMENTATION FOR OGI-BABA PRODUCTION
(1986-01) ADEYELE, S.
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.
STUDIES OF TOXIGENIC AND ZOOPATHOGENIC FUNGI ASSOCIATED WITH THE SPOILAGE OF NIGERIAN POULTRY FEEDS
(1988-03) ADEBAJO, L. O.
Six species of known toxigenic and zoopathogenic fungi were isolated from Nigerian poultry feeds. These include Aspergillus flavus Link: Fr. (IMI 280819), A. fumigatus Fres. (1M1 280822), A. niger v. Tieghem (IM1 280823), A. oryzae (Ahlburg) Cohn (IM1 280831), Rhizopus arrhizus Fischer (1M1 280827) and Rhizomucorpusillus Lindt Schipper (1MI 280824). Growth-temperature range for the fungi was between 15° and 45°C. Aspergillus fumigatus and Rhizomucor pusillus are thermotolerant with optimum growth 40° C while Rhizopus arrhizus had optimum growth at 30° C. For Aspergillus flavus, A. niger and A. oryzae the optimum growth was at 35° C. The pH growth studies showed that all the fungi had good mycelial growth at pH 4-8 with optimal growth at pH 5.5 for Aspergillus fumigatus, A. flavus and A. oryzae. Aspergillus niger, Rhizomtlcor pusillus and Rhizopus arrhizus had optimal growth at pH 6.0. Nutritional studies showed that all the fungi were capable of utilizing the various forms of carbon and nitrogen provided to varying extents. Starch and dextrin were excellent sources of carbon for mycelia growth and sporulation while pectin and carboxymethyl cellulose (CMC) were poorly utilized by all the fungal isolates. The fungal species grew poorly on native cellulose (filter papers) except Rhizomucor and Rhizopus arrhizus which showed no growth pusillus on this carbon source. Apart from tryptophan, all the nitrogen sources supplied were utilized for growth and sporulation by the test fungi though to the best nitrogen source varying extents. Casein was for all the fungi. Feed infusion medium also supported growth and sporulation of all the isolates. Varying quantities of aflatoxins (B(1), B(2_ and G(2)) were produced by Aspergillus flavus and A. oryzae on modified Czapek-Dox media. None of the remaining fungal species produced afaltoxin. Peak aflatoxin B(1) production was on the 8th day of incubation by the two toxigenic fungi. Optimum pH and temperature for the production of toxins were pH 5 and 300 C respectively. Major sources of aflatoxins in poultry feeds due to mould infestation in increasing order of importance were: palm kernel, corn and groundnut cake meals. Studies on aflatoxin production on feed concentrates by A. flavus and A. oryzae showed that under suitable conditions of moisture and temperature, dried brewers grains, wheat offals, palm kernel, corn and groundnut cake meals were suitable substrates for toxin production. Other feed concentrates: fish, blood, oyster shell and bone meals were found to be unsuitable substrates for aflatoxin production. Aflatoxins were not detected in poultry droppings before and after inoculation with the toxin producing fungi. All the fungal isolates produced extracellular amylases, cellulases, proteases and lipases. The synthesis and activity of these enzymes were affected by external factors such as the pH, incubation temperature and type of carbon source in the growth medium. Optimum activity for all the enzymes produced by the isolates was in acidic media (pH 4-6) and within a temperature range of between 40°C and 50°C. On the basis of these findings recommendations were made for the control of the toxigenic and zoopathogenic fungi in poultry feeds and other stored agricultural products.