Neobeguea mahafalensis Leroy. and Cedrelopsis grevei Baill. are the two Madagascan species which were investigated in this work. Neobeguea mahafalensis Leroy. belongs to the Neobeguea genus of the Meliaceae family and is a plant unique to Madagascar. It is commonly referred to as "Handy" by the native people of Madagascar, who use it as a medicinal plant. The stem-bark of N mahafalensis which has been analysed in this work, was collected from the dry, thorny forests of the deep south of Madagascar. Most species found in this region are unique in the world and are highly specialised in adapting to the very dry climate. The hexane extract was found to yield a limonoid (compound I) which has not been previously reported as a natural product. The known pentacyclic triterpenoid, j3-amyrin (compound II) and stigmasterol (compound III), were also isolated. Cedrelopsis grevei Bail!. is one of seven species of the genus Cedrelopsis which are confined to Madagascar. This species, commonly referred to as "Katrafay" by the Madagascan people, has undergone intensive chemical investigation as prior inclusion ofthis species in the Meliaceae family has always been questionable. The South African species Ptaeroxylon obliquum (Thung.) Radlk., is a member of the Ptaeroxylaceaefamily which is found to be so chemically similar to Cedrelopsis that the latter has been placed in the Ptaeroxylaceae family. The stem bark of Cedrelopsis grevei was obtained from the dry southern part of Madagascar and yielded a variety of chromones and coumarins, as well as stigmasterol (compound III) and the pentacyclic triterpenoid, j3-amyrin (compound II). Two chromones were isolated from Cedrelopsis grevei, namely ptaeroxylinol (compound IV) and ptaeroglycol (compound V). Ptaeroglycol has been previously isolated _from this species as well as from Ptaeroxylon obliquum whereas ptaeroxylinol has only byen isolated from Ptaeroxylon obliquum. Six coumarins were isolated from Cedrelopsis grevei in tillS study, all of which were 6,7-dioxygenated coumarins. These included the known compounds, scoparone (compound VI), O-methylcedrelopsin (compound VIII), norbraylin (compound X) and cedrelopsin (compound IX), as well as compound VII and compound XI which . have not been reported previously. No limonoids were isolated from this species in this investigation. / Thesis (M.Sc.)-University of Natal, 1997.

The thesis is divided into three parts. The first part looks at the reactivity difference between [Pt(terpy)(OH2)f+ and [Pt(bpma)(OH2)]2+ where terpy is 2,2' :6',2"-terpyridine and bpma is bis(2-pyridylmethyl)amine, towards thiols namely, L-cysteine, DLpenicillamine and glutathione. This is followed by a comparative study of [Pt(bpma)(OH2)]2+ and [pd(bpma)(OH2)f+. Finally the reactivity differences between [Ru(terpy)(bipy)(OH2)f+ and [Ru(terpy)(tmenXOH2)]2+ are reported. Included are the synthesis and characterization ofthe complexes. The substitution behaviour of [pt(terpy)(OH2)]2+and [Pt(bpma)(OH2)f+ was studied as a function of entering thiol concentration and temperature. The reactions between the Ptcomplexes and DL-penicillamine, L-cysteine and glutathione were carried out in a 0.10 mol dm03 aqueous perchloric acid medium using stopped-flow or conventional UV-Vis spectrophotometry as required. The observed pseudo-first-order rate constants for the substitution reactions are given by kobs = k2[thiol] + k 2. The k 2 term represents the reverse solvolysis reaction. This term was found to be zero for Ptn(terpy) which was the most reactive complex. The second-order rate constants, ka; for the three thiols varied between 0.107±0.001 M·l S·l and 0.517±0.025 M"l sol for PtlI(bpma) and 10.7±0.7 M"l S·l to 711.9±18.3 M"l S·l for PtlI(terpy), with glutathione being the strongest nucleophile. Analysis of the activation parameters, Mf' and .1.S", clearly shows that the substitution process is associative in nature. The second study has looked at the substitution of the coordinated water molecule from [Pt(bpma)(OH2)f+ and [pd(bpma)(OH2)f+ by a series of nucleophiles [Nu] viz. TU, DMTU, TMTU and as well as Be", Cl', SCN", and r for the Ptn(bpma) complex. The investigation was conducted under pseudo-first-order conditions as a function of concentration of [Nu] as well as temperature for PtlI(bpma) complex using stopped flow spectrophotometry. Reactions involving PdII(bpma) were done at 10°C. The observed pseudo-first-order rate constants obeyed the equation kobs= k2[Nu]. The second-order rate constants, kz, at 10 "C for the sulfur donor nucleophiles have been found to vary between 70.35 M I sol and 223.06 M I sol for PtII(bpma) and (1.24 ± 0.01) x 105 M I sol to (2.17 ± 0.02) x 105 M-Is-l for PdII(terpy), with DMTV being the strongest nucleophile. The second-order rate constant, ka; at 25 "C fur PtII(terpy) was found to increase in the following order cr < Be" < TMfU < SCN < TV < DMTV < f. This order is in agreement with the polarizability of the nucleophiles, the nucleophilic discrimination factor being 0.38. The temperature studies for PtII(bpma) suggest that the substitution process is associative in nature.n The third part looked at the reactivities of [Ru(terpy)(bipy)(OHz)]z+ and [Ru(terpy)(tmen)(OHz)]z+ where bipy is 2,2'-bipyridine and tmen is N,N,N ',N 'tetramethylethylenediamine with three nucleophiles TV, DMTV and CH3CN. The pKa values for the complexes were found to be 9.99 and 10.27 for [Ru(terpy)(bipy)(OHz)]z+ and [Ru(terpy)(tmen)(OHz)f+, respectively. The substitution of water involving the two complexes was studied under pseudo-first order conditions using UV-Visible Spectrophotometry. The pseudo-first-order rate constant fitted the simple rate law kobs = kz [Nu] + k-z. The k.z term was found to be zero for [Ru(terpy)(bipy)(OHz)f+ but nonzero for [Ru(terpy)(tmen)(OHz)]z+. The values of the second order rate constants (kz) for the three nucleophiles were found to be between (1.08 ± 0.02) x 10-4 M l sol and (15.0 ± 0.27) x 10-4 M-l sol for [Ru(terpy)(bipy)(OHz)]z+ and (0.82 ± 0.04) x 10-4 M-l sol and (21.90 ± 0.69) x 10-4 M-I sol for [Ru(terpy)(tmen)(OHz)]z+. The results suggests that nback donation accounts for the difference in reactivity. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

Four species belonging to the Hyacinthaceae family were investigated. The taxonomy of the Hyacinthaceae is currently under review and therefore compounds isolated from these plants could provide valuable chemical evidence which taxonomists could find very useful. The bulbs of the species investigated have been reported to have widespread uses in traditional African medicine, being used by different local tribes to treat a variety of ailments ranging from use as a soothing medicine for pregnant women to their being used as an ethnoveterinary medicine. The bulbs of Ledebouria cooperi are specifically used as an anti-inflammatory agent during circumcision ceremonies. The bulbs investigated were found to contain homoisoflavonoids, a class of compounds known to be specifically responsible for the anti-inflammatory properties of these plants when used by traditional healers. The bulbs of L. cooperi were found to contain two known homoisoflavonoids as well as a triterpenoid. Malic acid was also isolated from the methanol extract. A further homoisoflavonoid of the 3-benzyl-4-chromanone type was isolated from Scilla plumbea. Drimiopsis maculata was found to be an abundant source of natural products from which two scillascillin-type homoisoflavonoids as well as two aromatic compounds were isolated. Investigation into the fourth species, Drimia robusta, yielded an uncommon bufadienolide. As no spectroscopic information was available for this compound, the complete assignment of the compound was performed using 2-D NMR spectroscopy. / Thesis (M.Sc.)-University of Natal, Durban, 2000.

Bulbs of Scilla natalensis Planch, Scilla nervosa (Burch.) Jessop, Scilla dracomontana Hilliard and Burt and Scilla kraussii Bak. (Hyacinthaceae) were investigated. The plants are widely used by the local African people for a variety of ailments that inflict them and their livestock. Plant material was harvested in different localities i.e. KwaZulu-Natal (KZN) and Mpumalanga (Mpl). The bulbs have been found to contain homoisoflavonoids and stilbenoids. Ten homoisoflavonoids and two stilbenoids were isolated. Of the ten homoisoflavonoids isolated, nine were of the 3-benzyl-4-chromanone type while one was a 3-benzylidene-4-chromanone. Four of the 3-benzyl-4-chromanones were found to be novel compounds while others were recognised as having been reported before from other genera within the family Hyacinthaceae viz., Eucomis and Muscari. The 3-benzylidene-4-chromanone type compound isolated was also found to be a known compound. The stilbenoids, on the other hand, are reported for the first time in this genus although they seem to have a wide distribution in the plant kingdom. The structures of the isolated compounds were elucidated using spectroscopic methods. / Thesis (M.Sc.)-University of Natal, Durban, 1998.

Industrial catalysts used in commercial processes for the production of maleic anhydride are mainly Vanadium Phosphorous Oxide (VPO) catalysts. The VPO catalyst used is Vanadyl Pyrophosphate (VO)2P207 made from its precursor Vanadium Phosphorous Hemi-Hydrate VOHP04.O.5H20 in an non-aqueous medium. In order for the VPO catalyst to perform optimally, a metal promoter, Ru, was selected as the doping agent in this study. Four catalysts of different metal doping concentrations (undoped, 0.2%, 0.6% and 1%) were subjected to the oxidation of n-butane. Promoters are added to facilitate the oxidation of n-butane to maleic anhydride. n-Butane gas is now being used in many industrial processes, in fixed bed reactors to convert the gas to maleic anhydride. Catalysts were calcined under high temperatures under a nitrogen atmosphere. It was found that with an increase in reaction temperature, there was an increase in conversion of n-butane to maleic anhydride. Selectivity of the product also showed an increase with an increase in temperature at a Gas Hourly Space Velocity (GHSV) of 1960-2170hr-1. Catalysts were characterized using different techniques such as Electron Dispersive X-Ray Spectroscopy, Inductively Coupled Plasma-Atomic Emission Spectroscopy, Fourier Transform - Infra Red, Average Oxidation State, Brunauer Emmett and Teller (surface area), X-Ray Diffraction and Scanning Electron Microscopy. The 0.6% Ru promoted VPO catalyst showed to be most effective in terms of conversion, selectivity and yield, at a temperature of 450°C as compared to the other catalysts studied. The catalysts degenerated after being subjected to higher temperatures. The selectivity obtained by this catalyst was at 70.2% and the yield obtained was 37%. This study showed that with an increase in Ru up to a certain concentration (0.6%), an increase in selectivity and yield was observed, thereafter, with additional Ru doping, a decrease in selectivity and yield was obtained. / Thesis (M.Sc.)-University of Natal, 2003.

Co promoted and unpromoted vanadium-phosphorous-oxide (VPO) catalysts were synthesized via an organic route. The catalyst precursor was calcined and then conditioned in a reactor, forming the active vanadyl pyrophosphate, (VO)2P2O7, phase. Different promoter loaded catalysts were synthesized and their effect on the yield of maleic anhydride (MA) from n-butane oxidation was examined at different temperatures and gas hourly space velocities (GHSV). The catalysts were tested as a powder. The catalysts were examined in the oxidation of n-butane gas, over air as an oxidant, in a specially designed and constructed continuous flow, fixed-bed catalytic micro-reactor equipped with an on-line gas chromatography (GC) monitoring system. A thermal conductivity detector (TCD) was employed for carbon oxide monitoring and a flame ionization detector (FID) for all other products. The catalysts were characterised by X-ray diffraction (XRD) to determine the phases present in the precursor, calcined and used catalysts. The Brunauer-Emmet-Teller (BET) surface area was calculated for the different promoter loaded catalysts. Fourier transform infrared (FT-IR) spectra, via the KBr pellet method, and attenuated total reflectance (ATR) spectra were recorded to determine the anions present in the bulk and surface of the catalyst respectively. Energy dispersive X-ray (EDX) and inductively couple plasma-atomic emission spectroscopic (ICP-AES) techniques were employed to determine the elemental composition on the surface and in the bulk of the catalyst respectively. Scanning electron microscopic (SEM) images of the catalysts during different stages of their investigation were recorded. The average vanadium oxidation state (AV) in the bulk of the catalyst was determined via a titrimetric method. The catalysts were optimized to a high yield and selectivity of MA. The operating temperature, GHSV and promoter loading on the catalyst were the parameters that were changed during the testing of the catalyst. Different stages of the catalyst's life were characterised via the techniques mentioned above. The catalysts were monitored over a 200-hour period on average, usually taking approximately 24 hours to equilibrate. One such Co promoted catalyst yielded 45 % MA at 275°C and GHSV of 2878 hr-1 on equilibration, with an n-butane conversion of 73 %, whilst all previously reported VPO catalysts produce far lower MA yields at this temperature. / Thesis (M.Sc.)-University of Natal, Durban, 2002.

Mondi Ltd. operates a deinking plant at its Merebank mill. The plant recycles 85 000 tons per annum of flat news and magazine to produce a furnish for its newsprint papermachines. A review of the relevant pulping and flotation chemistry literature revealed that the role played by sodium silicate appears to be multi-faceted and in some dispute. Sodium silicate has an undisputed role in pH buffering, hydrogen peroxide stabilisation and the prevention of fibre yellowing. However, its role in deinking is said to be that of an ink collector or alternatively an ink dispersant. The mill's own experience has shown that the sodium silicate plays a vital role in the deinking process. Sodium silicate's ability to disperse ink, both alone and in the presence of calcium ions and fatty acid soaps, was investigated using a model ink system. A representative newsprint ink base was dispersed in the laboratory under conditions similar to those encountered in a deinking pulper. The resultant dispersions were studied using turbidity and particle size analysis. The morphology of the ink particles was determined using a scanning electron microscope. Sodium silicate proved to be a poor disperser of ink particles, but nevertheless appeared to greatly influence the dispersing properties of the soap in the presence of calcium ions. The nature of the interactions between sodium silicate, calcium ions and the collector soap were studied in an attempt to elucidate the role of sodium silicate. A model system consisting of the sodium salt of collector soap, calcium ions and sodium silicate was studied under the conditions that prevail in a typical newsprint deinking pulper. It was found that the soap and the sodium silicate compete for the calcium ions, and sodium silicate showed a measurable chelating e:ffect on calcium ions. Thus, increasing levels of sodium silicate lead to an increase in the concentration of sodium soap in solution. It was hypothesised that this effect would lead to better dispersion of ink particles and improved deinking performance. This chelating effect was evaluated in laboratory deinking studies. Samples of newsprint were pulped in a 251 Lamort laboratory pulper under a variety of conditions, viz. with fresh water, with an excess of soap, with an excess of calcium, with and without sodium silicate. The pulps were floated in a 201 flotation cell. The brightness and colour of the unfloated and floated pulps were measured. The level of the final brightness after flotation was taken as a measure of deinking efficiency. The highest final brightness was achieved when there was an excess of sodium soap and a low Ca hardness in the pulper. Softening the water used in pulping without adding excess sodium soap did not significantly improve pulp brightness. The lowest final brightness occurred in the presence of an excess of calcium in the pulper. Calcium in the pulper in the presence of sodium silicate did not result in a significantly lower final brightness. The results support the hypothesis that sodium silicate sequesters the soluble calcium in a pulping system, thereby increasing the sodium soap concentration and the resultant deinking performance. Apart from sodium silicate's chief role as a peroxide stabiliser, the sequestering action on calcium appears to be its main mechanism of action in a deinking system. An appreciation of this role will facilitate the optimisation of deinking systems with respect to calcium hardness and silicate concentration. To this end it was recommended that the Merebank deinking plant should evaluate the use of water with a low calcium ion concentration and the addition of some soap into the pulper to improve their deinking plant performance. / Thesis (M.Sc.)-University of Natal, Durban, 2003.

Environmental and nutritional imperatives make it necessary to carry out regular and reliable / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2007.

The effect of ozone on the inactivation of two Gram-negative strains (Escherichia coli and Pseudomonas aeruginosa) and one Gram-positive endospore (Bacillus subtilis) bacteria, often present in water and the cause of some waterborne diseases was investigated as a function of ozone concentration and ozonation duration. Ozone was generated in situ using corona discharge methods where the ozone concentration ranged from 0.906 - 4.724 mg/L and the inactivation of the three microbes followed pseudo-first order kinetics with respect to the microbes. Three microbes were cultured and the influence of temperature and pH of the aqueous systems on the ozone initiated inactivation rate of the three microbes was also investigated. This study reports that molecular ozone is more effective than hydroxyl radicals initiated by the ozone chain reactions. Two suggested mechanisms for the antimicrobial effectiveness of ozone in water systems from the literature is discussed. The study also found that ozonation significantly decreased the Biological Oxygen Demand (BOD) value of natural water. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2008.

Three species have been investigated in this project: Iso-ocobullenone (p 23) and its probable precursor (p 27) have been isolated from the leaves and bark of Ocotea kenyensis. This is only the second time that these compounds have been isolated and the first time from this species. The isolation of these two compounds in the leaves establishes a commercially important chemical link with the bark. The bark of the closely related Ocotea bullata is the most sought after source of "muthi" in the Kwa-Zulu Natal region and it is becoming a very scarce commodity. The leaves of Ocotea kenyensis have also yielded related compounds including A8'-3,5-dimethoxy-3',4'-methylenedioxy-l ',2',3',4'-tetrahydro-6' -oxo-7,1',8,3'-neolignan which is described here for the first time. Other compounds isolated were bacterialprenol, triacontane, B-sitosterol and a previously undescribed isoprenoid. An investigation into the molluscicidal potential of compounds in Apodytes dimidiata was extended with a view toward control of the population of the intermediary snail host for bilharzia-causing trypanosomes. This study afforded the known compounds squalene, lupeol, betulinic acid and catechin. The synthesis of a previously isolated compound, 4-ethyl catechol, with molluscicidal activity was successfully completed and its structure and activity were confirmed. A bio-assay guided isolation procedure was used to determine the potential value of compounds in Ehretia rigida for the control of sleeping sickness. Allantoin, a- and B-amyrin, triacontanol and B-sitosterol were isolated. Activity of the extracts was not high enough to be of commercial value. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998