Chemistry

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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.
Assessment and remediation of heavy metals contaminated soils
(Depet Publishers, 2016) Ogundiran, M.B; Osibanjo, O.
CHEMICAL COMPOSITION OF THE ESSENTIAL OILS OF FIVE FRUIT TREES AND NON-VOLATILE CONSTITUENTS OF Theobroma cacao L. POD-HUSK
(2016-08) FATIMAH, T. I.
Essential Oils (EOs) are volatile secondary metabolites characterised by a strong odour and widely used for pharmacological and industrial applications. There is dearth of information on chemical compositions and bioactivities of EOs of some fruit trees in Nigeria. This study was therefore designed to extract and characterise the EOs from selected fruit trees, screen the EOs for bioactivity as well as to isolate and characterise non-volatile constituents from Theobroma cacao L. pod-husk due to its availability. The plant samples (Carica papaya L., Theobroma cacao L., Persea americana M., Ananas comosus (L) Merr and Chrysophyllum albidum G. Don) were collected in Ibadan, identified and authenticated at the Herbarium of Forest Research Institute of Nigeria, Ibadan. Essential oils were extracted from the leaves, stem-barks, root-barks, fruits, peels, pod-husk and seeds of the plants using hydro-distillation method and analysed by Gas Chromatography (Flame Ionization Detector and Mass Spectrometry) techniques. The antibacterial activity of the EOs at 20 µg/mL was assayed on two Gram-positive and four Gram-negative bacteria using Microplate Alamar Blue Assay measured in UV/Visible spectrophotometer. The antioxidant activity of the EOs at 20 µg/mL was determined by radical scavenging procedure while insecticidal activity was evaluated by contact toxicity test using three grain pests. Pure compounds were isolated from methanol extract of T. cacao pod-husk by chromatographic techniques. The chemical structures of the compounds were elucidated using Infrared, Nuclear Magnetic Resonance and Mass Spectroscopic techniques. Data were analysed using descriptive statistics. Twenty-seven EOs were obtained and their yield ranged from 0.1 to 1.2% (v/w). The major components in P. americana EOs were β-caryophyllene (12.7%; leaf), tetradecanal (31.8%; root-bark), globulol (25.4%; peel), (Z,Z)-4,15-octadecadien-1-ol acetate (21.8%; seed), tetradecanal (24.9%; stem-bark) and p-xylene (40.5%; fruit). Carica papaya EOs mainly comprised benzylisothiocyanate (89.1%; seed), octadecanol (62.5%; root), octadecanol (71.1%; stem), m-xylene (35.1%; stem-bark), heptadecanol (25.2%; fruit), phytol (21.8%; leaf), benzylisothiocyanate (71.5%; root-bark) and 9-hexadecen-1-ol (16.9%; peel). P-xylene (62.4%; fruit), p-xylene (29.9%; shoot) and tetradecanoic acid (8.6%; peel) dominated A. comosus EOs. The principal constituents in T. cacao EOs were hexadecanoic acid (78.7%; leaf), o-xylene (53.3%; seed), ledol (33.6%; pod-husk) and β-bisabolol (17.3%; stem-bark). The dominant compounds in C. albidum EOs were m-xylene (66.7%; seed), p-xylene (21.4%; seed-bark), ethylhexadecanoate (19.9%; leaf), hexadecanoic acid (14.7%; stem-bark), m-xylene (53.1%; root-bark) and hexadecanoic acid (14.7%; fruit-bark). The chemical constituents for twenty-one of the EOs of the fruit plants were obtained for the first time ever. Theobroma cacao leaf EO exhibited the highest inhibition against Gram-negative bacteria at 78.6%, while P. americana fruit and peel EOs showed the highest inhibition against Gram-positive bacteria at 69.9%. Persea americana fruit and seed EOs displayed the highest and lowest radical scavenging activity at 42.1 and 1.2%, respectively. The EOs showed activity between 0 to 20% in insecticidal assay. Column chromatography of the methanol extract of T. cacao pod-husk yielded three known triterpenes: 24-hydroxy-9,19-cycloanost-25-en-3-one, stigmast-5-en-3β-ol and ergosta-5α,8α-epidioxy-6,22-dien-3β-ol. The EOs have antibacterial and antioxidant properties which is indicative of their potential as sources of pharmaceuticals.
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.
Comparison of organic chelators and compost assisted phyoremediation of a lead slag-contaminated soil by Sporobolus fertilis and Gomphrena serrate
(2015) Ogundiran, M.B.; Kemie, E.A.; Adejumo, S.A.
COMPUTATIONAL STUDY ON POLYMERS OF UNSUBSTITUTED AND SOME SUBSTITUTED PYRROLES
(2015-09) IBEJI, C. U.
Conjugated polymers which interact with biological systems have attracted interest due to their high conductivity, stability and electronic properties. Substituted polymers of 3-methyl pyrrole-4-carboxylic acid (MPCa) have been synthesised and used as components of biosensor, while unsubstituted polypyrroles are not effective for such application. However the mechanism of interaction, nature, the relative importance of dynamic and static electron correlation of the polymers are not completely understood. This research was designed using computational approach to study the molecular properties of substituted and unsubstittued pyrrole polymers with a view to understanding what make polymers of substituted pyrroles suitable components of biosensor. Structures of unsubstituted Pyrrole (Py); substituted pyrroles which include 3-methyl- pyrrole-4-carboxylic acid (MPCa), 3-methyl-pyrrole-4-carboxamide (MPCam), 3- methyl-pyrrole-4-sulfonic acid (MPSO3H), 3-methyl-pyrrole-1-carboxylic acid, (MPCb), 3-methyl-pyrrole-4-carbothioic acid (MPCOSH), 3-methyl-pyrrole-4- carbaldehyde (MPCHO) and their polymers were studied using quantum mechanical approach. The molecular properties investigated were Energy gap (Eg), Koopman’s reactivity descriptors, Fukui function, Lowest Unoccupied Molecular Orbital (LUMO), Highest Occupied Molecular Orbital (HOMO) and thermodynamic properties. These were calculated using restricted hybrid density functional theory with Becke three, Lee Yang and Parr at 6-31G(d) basis set. The calculated Eg were extrapolated to polymer through second order-degree polynomial equation. Spin-flip time density functional theory and coupled cluster single and double method with 6-311++G(d,p) basis set were used to calculate Coupled Cluster operator (T1) diagnostic and Vertical Singlet- Triplet (VST) gap to accurately determine polymers suitability as components of biosensor. All calculations were carried out using quantum mechanical software. The calculated Eg of the polymers decreased with increasing chain length and the nature of substituent. The order of Eg was MPCHO > Py > MPCb > MPCa > MPCam > MPSO3H > MPCOSH, with MPCOSH having the lowest value of 1.7 eV. Substituted polypyrroles except MPCHO have stronger electron-electron interactions since electron-electron interaction is more when the Eg is low (between 1.0 and 3.0 eV). Koopman’s reactivity descriptors were within the range of -3.9 to 2.4 eV (chemical i potential), 1.5 to 2.1 eV (chemical hardness) and 1.4 to 4.4 eV (electrophilicity index). Fukui function revealed a high electron density around the substituted functional groups and the LUMO and HOMO were extended over the C-C and C=C bonds. Thermodynamic parameters were enthalpy change (-4361.1 to -1045.7 kJmol-), entropy change (540.3 to 952.2 Jmol-1K-1) and free energy change (∆G0f) (-4361.2 to - 1045.8 kJmol-1) indicating spontaneous formation of the polymers. The T1 diagnostic of unsubstituted polypyrroles ranged from 0.0015 to 0.0013, while substituted polypyrroles ranged from 0.030 to 0.065. The T1 <0.02 indicated that unsubstituted polypyrrole had dynamic correlation with single reference (closed shell), while T1 >0.02 showed that substituted polypyrroles possessed static electron correlation with multireference (open shell) nature. The VST gap of unsubstituted polypyrroles ranged from 3.0 to 4.8 eV, while substituted polypyrroles ranged from 3.1 to 5.3 eV. The VST gap >0 revealed that all studied systems have a singlet ground state. The presence of substituents on polypyrrole decreased the energy gaps which led to the enhancement of their molecular properties making them suitable components of biosensor.
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.
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
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.
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.
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.
Evaluation of heavy metals bioaccumulation potentials of plants grown on waste contaminated soils.
(2011) Ogundiran, M.B; Osibanjo, O.
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.
Global management of electronic wastes: challenges facing developing and economy‐in‐transition countrie
(John Wiley & Sons, Ltd, 2016) Ogundiran, M.B; Osibanjo, O; Nnorom, I.C; Adie, G. U; Adey, A.A
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
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.
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.
ISOLATION AND CHARACTERISATION OF SECONDARY METABOLITES FROM Dioclea reflexa (HOOK F.) AND Cussonia arborea (HOCHST)
(2014-07) ABDULKABIR, O. O.
The discovery of bioactive natural products is a basis for development of novel pharmaceuticals. Indigenous medicinal plants which are largely unexplored offer chemical diversity with structural complexity and biological potency. Despite their ethnomedicinal usage, there is little information on the bioactive components of Dioclea reflexa and Cussonia arborea. This study was designed to isolate and characterise the secondary metabolites from the roots of D. reflexa and C. arborea, and evaluate free radical scavenging activity of the isolates. One kilogramme each of authenticated D. reflexa root and C. arborea root-bark were collected from Eruwa, Oyo State. The air-dried samples of D. reflexa and C. arborea were purposively extracted with ethanol and methanol respectively. The crude extracts were separately fractionated on silica gel column chromatography with gradient elution using various solvents. The sub-fractions were further subjected to a combination of chromatographic techniques for isolation of pure compounds. Structures of isolated compounds were elucidated using one and two-dimensional Nuclear Magnetic Resonance (NMR), Infrared (IR), Ultra-Violet-Visible and Mass Spectroscopy (MS) techniques, and comparison with literature data for known compounds. The isolated compounds were evaluated for free radical scavenging potential in comparison with butylated hydroxyanisole following standard method. The ethanol extract (85 g) of D. reflexa on column chromatography gave β-sitosterol 1, lupeol 2, aurantiamide acetate 3, mearnsetin 6, 7,4′-dihydroxyflavone 7 and 3,5-dihydoxy-4-methoxybenzoic acid 8. The column yielded two new compounds, named lexaflavanone 4 and reflevone 5. Lexaflavanone showed the presence of sixteen carbons: 8C, 1CH2, 6CH and 1CH3. The MS gave M+ peak at m/z 302.0769 (Calcd. 302.0792), with 10 degree of unsaturation, corresponding to C16H14O6. The NMR signals were seen at δ 8.53, 7.70 (1H, d, J= 8.5 Hz), 6.58 (2H, s), 6.55 (1H, dd, J= 2, 8.5 Hz), 6.42 (1H, d, J= 2Hz), 5.36 (1H, dd, J= 2.5, 12.5 Hz), 2.93 (1H, dd, J= 12.5, 17 Hz, H-3axial) and 2.66 (1H, dd, J= 3, 17 Hz, H-3equi). The IR absorptions (υmax, cm-1) for OH (3361) C=O (1652) and C-C in ring (2917) were also detected. Reflevone, molecular formula C16H12O6 suggested δH signals: 6.54 (1H, s), 6.97(1H, dd), 7.02(1H, d) and 7.06 (2H, s), and δC signal: 177.9 (C=O) typical of flavone. In addition, its infra-red stretching absorptions (υmax, cm-1) revealed C-H sp2 (1570) and O-H (3377). The characteristics peaks of retro-Diels-Alder cleavage of ring C were observed in MS spectrum at m/z 137 and 166. Column chromatography of the methanol extract (18 g) of C. arborea yielded three known compounds, stigmasterol 9, oleanolic acid 10 and hederagenin 11 when compared with literature. The compounds were however new to the species of C. arborea. Lexaflavanone, reflevone and hederagenin exhibited free radical scavenging activity with IC50 of 58.14, 322.0 and 105.0 μM respectively. The plants have potentials for the development of drugs for the treatment of diseases with oxidative stress due to their free radical scavenging activities. Lexaflavanone and reflevone obtained from D. reflexa are new additions to the library of chemical compounds.
ISOLATION OF DIOSGENIN FROM Smilax kraussiana MEISN EX. KRAUSS AND SYNTHESIS OF ITS DERIVATIVES AS ANTICANCER AGENTS
(2015-08) HAMID, A. A.
Plants remain a major source of novel drugs for the treatment of various diseases like cancer. The search for safe anticancer drugs from plants has led to the discovery of camptothecin and taxol. Smilax kraussiana is used in herbal medicine to treat tumors, veneral and skin diseases. Many plants including S. kraussiana are still underexploited despite their ethnomedicinal properties. This study was designed to isolate and characterise the constituents of S. kraussiana, synthesise active derivatives from the most bioactive isolate and evaluate the anticancer activities of the extracts and compounds. The leaves and stems of S. kraussiana were collected from Onigambari Forest Reserve, Ibadan and authenticated at Forestry Research Institute of Nigeria (Voucher number: FHI 108799), Ibadan, Oyo State. The samples were air-dried, pulverized and successively extracted with hexane, ethyl acetate and methanol. The extracts were subjected to chromatographic techniques to obtain pure isolates. Structural elucidation of the isolated compounds was done using 1D, 2D Nuclear Magnetic Resonance and Mass Spectroscopic methods. Isolated diosgenin was synthetically modified by oxidation, reduction, and condensation reactions. The extracts, isolates and synthesised compounds were evaluated for anticancer activities against four human cancer cell lines; leukaemic (K-562), hepatic (WRL), breast (MCF-7) and colorectal carcinoma (COLO) at 20, 50 and 100 µM concentrations using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and Sorphordamine assays. Tamoxifen was used as positive control for both assays. Data were analysed using descriptive statistics. The successive extraction of S. kraussiana with hexane, ethyl acetate and methanol yielded 14.0, 20.0 and 11.5 g of the extracts respectively. Chromatographic separation of hexane, ethyl acetate and methanol extracts resulted in four, nine and six compounds respectively. The isolates are mainly triterpenoids, steroids and fatty acids, while the most abundant isolate was diosgenin (3β-hydroxy-5-spirostene) (80.0 mg = 0.5 %). The modification of diosgenin via two synthetic reaction schemes yielded fifteen and twelve compounds respectively. The new analogues obtained from the first scheme included (22β)-25-oxo-27- nor-furost-5-en-3β-acetate, (22β)-25-hydroxy-3β-yl-27-nor-furost-5-en-3β-acetate, (22β)- (Z)-26-(4′-nitrobenzylidene)-3β-yl-furost-5-en-3β-acetate, (22β)-26-(3′,4′,5′- ii trimethoxybenzylidene)-3β-yl-furost-5-en-3β-acetate, 3β-acetoxy-furost-5-en-26-aldoxime and 3β-acetoxy-27-nor-furost-5-en-25-ketoxime. The new compounds from the second scheme included (22β,25R)-3β-acetoxy-spirost-5-en-7-one, (22β,25R)-3β-acetoxy-spirost- 5-en-7-ketoxime, (22β,25R)-spirost-3,5-dien-7-one, (22β,25R)-3β-acetoxy-7-(4′- nitrobenzylidene)-spirost-5-en-3β-yl, (22β,25R)-3β-acetoxy-spirost-5-en-3β-yl-7-(ethyl-3′- propanoate)-ketoxime and (22β,25R)-3β-acetoxy-spirost-5-en-3β-yl-7-(ethyl-4′-butyrate)- ketoxime. Nineteen out of the 27 synthesised compounds are reported for the first time. Ethyl acetate and methanol extracts of S. kraussiana exhibited cytotoxic activity against WRL and COLO cell lines with IC50 of 46.1 and 90.0 µM, but showed low inhibition on K-562 and MCF-7 with IC50 of 113.0 and 236.0 µM respectively. Hexane extract exhibited low activity against the four cell lines with IC50 between 130.0 and 310.0 µM. The most bioactive isolate, diosgenin showed cytotoxic activity against the four cell lines by suppressing the viability of cells with IC50 between 12.3 and 38.0 µM, while active synthesised compounds inhibited the growth of the four cell lines with IC50 between 7.5 and 35.5 µM. The phytochemical constituents of Smilax kraussiana extracts justify their use in herbal medicine. The isolated compounds are reported for the first time from the plant. The synthesised diosgenin derivatives could serve as lead compounds for further investigation as anticancer agents.
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.