Even though early man did not know the nature of coloring matter in flowers, he used the coloring matter as dye for centuries. There are a variety of reasons for the interest of chemists in natural and artificial coloring matters. One of these is the color pleasure, anothe1· is the commercial importance. The visible color facilitates the experimental work in the search for methods if separation, purification and determination of organic structures. Search for the knowledge of coloring matter goes far back in history. Man has dyed his textiles with the help of mordants from the most ancient times up to the time of Perkin's discovery of mauve. Then a new era in dyestuff chemistry commenced. In the first half of the nineteenth century with the rise and development of the study of Organic chemistry much attention was directed to the extraction and characterization of pure coloring matters from natural sources .... usually the bark, leaves, fruits. or sap of trees or plants. During the twentieth century -- and just a little before that--great progress has been made in the synthesis of many typical natural coloring matters and the improved technique and novel synthetical methods which will bear upon the general progress of chemistry. This research was done with the purpose of isolating and identifying the coloring matter in the flowers of Vinca Major, with the common name of periwinkle. This was done by extracting the pigment of the flowers with methanol, amyl alcohol, and crystallizing the pigment as a chloride. For this pigment, solubility, color reactions, spectra and other physical properties were obtained.

<p>Since Helichrysum is known by the indigenous people of Africa for therapeutic properties, such as against colds, flu and wounds, the aim of this study was to focus on the patulum species found predominantly in the Western Cape region of South Africa and by means of isolation and identification of the plant constituents, be able to relate the therapeutic activity on the basis of literature precedents, to the compounds extracted.</p>

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.

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.

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

Chromatographic methods were used to determine the absolute values of cis-aconitic acid and trans-aconitic acid present in sugar cane factory processing streams and to determine the rates of isomerisation from the trans-aconitic acid to the cis-aconitic acid isomer. A reproducible, solid phase, ion exchange extraction method was developed to isolate the organic acids found in sugar factory process streams. The isolated acids were quantified using a dual ion-exclusion column, high performance liquid chromatographic method. To improve resolution of the acids, columns were maintained at different temperatures, whilst the combined use of both ultra-violet (UV) and refractive index detection proved useful in peak identification. Concentrations of the aconitic acid isomers were used to calculate the cis/trans aconitic acid isomer ratio occurring across the different processes found in a sugar cane factory. trans-Aconitic acid was found to be the predominant form present in the cane entering the factory. Analysis showed that isomerisation of the trans-aconitic acid to the cis-aconitic acid isomer occurred during processing. To understand and model this reaction, a reproducible experimental isomerisation method was developed making use of buffers to maintain pH conditions during experiments. A chromatographic analysis method, using ion-exclusion chromatography and UV detection, was developed to analyse the isomerisation reaction mixture. Chromatography was used in both an on-line and off-line mode for quantitation of the isomers. The method was used to study the isomerisation under conditions similar to those found in the factory. These included pH, temperature, ionic strength and the presence of monovalent and divalent cations found in sugar cane juices. It was shown that the isomerisation is a first order reversible reaction under the conditions studied. Temperature and pH were shown to be the important isomerisation variables. Temperature enhances the rate of isomerisation of the trans-aconitic isomer to the cis-aconitic acid isomer whilst pH affects the ultimate cis/trans aconitic acid ratio attained. Ionic strength was found to be a relatively unimportant factor. The presence of divalent and monovalent cations, at concentrations usually found in cane juice, was shown to have little effect on the rate of isomerisation. Activation parameters, including the activation energy (Ea), pre-exponential factor (log A), enthalpy (?H‡) and entropy of activation (?S‡), were calculated at each combination of buffer concentration and pH used in the experimental procedures. The values recorded are of a similar value to those reported for structurally similar compounds. cis-Aconitic acid was shown to undergo decarboxylation to itaconic acid. This occurred at low pH values and high temperatures. A detailed study was not undertaken since the conditions under which it occurs are considered extreme from the viewpoint of a sugar technologist. A model describing the equilibrium cis/trans aconitic acid isomer ratio was developed as a function of pH, temperature and time from the kinetic results. This was used to predict the equilibrium ratio for the aconitic acid isomers at the output of various processes in the sugar factory. Given the time, average pH and temperature the model can successfully predict the equilibrium ratio for the relevant process stream. / Thesis (M.Sc.)-University of Natal, Durban, 2000.

The wood, leaf and seed extracts of Apodytes dimidiata, Turraea floribunda and Turraea obtusifolia were examined. Two new limonoids belonging to the Toonafolin group were isolated from the seeds, two known havanensin-type limonoids were isolated from the leaves and both stigmasterol and sitosterol were isolated from the wood of Turraeafloribunda. Sitosterol as well as a limonoid which could not be characterised were isolated from the seeds, phytol, melianone and a protolimonoid similar to sapelin-F were isolated from the leaves and three protolimonoids: melianodiol, melianotriol and 7,8-dihydroturraeanthin 3-acetate were isolated from the wood of Turraea obtusifolia. An ester was isolated from the seeds of Apodytes dimidiata. Appropriate reactions were performed, where possible, on the compounds isolated. / Thesis (M.Sc.)-University of Natal, Durban, 1990.

Ledebouria zebrina and Scilla natalensis Planch were the two species investigated in this work. Ledebouria zebrina belongs to the Hyacinthaceae (Liliacea sensu lato) and to this date, the chemical composition of this species has not been investigated. Members of this family are found in southern Africa. The Ledebouria genus was formerly classified as part of the Scilla genus from which a large member of naturally occuring oxygen heterocycles known as homoisoflavanones have been isolated. In this work the bulbs of L. zebrina were investigated and five compounds were isolated. Three compounds were of the homoisoflavanone type while the remaining two belong to the eucosterol type triterpernoids. Scilla natalensis Planch also belongs to the Hyacinthaceae family. Previous chemical investigations of the bulbs of this plant yield two homoisoflavanones of the 3-benzyl-4- chromanone type. Members of this family are mostly found in the Eastern parts of the country, ranging from the Eastern Cape to Mpumalanga province including Lesotho and Swaziland. The bulbs of this plant were investigated and this yielded ten compounds. The structures of the isolated compounds were elucidated using spectroscopic methods. / Thesis (M.Sc.)-University of Natal, Durban, 2001.

by Ching-hung Wong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 75-78). / Chapter i --- Biography / Chapter ii --- Abstract / Chapter iii --- Acknowledgments / Chapter iv --- Abberivations / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Review on the published syntheses of Zoapatanol --- p.1 / Chapter 1.2 --- Review on the construction of the oxepane ring --- p.7 / Chapter 1.3 --- "Review on the intramolecular nitrone and nitrile oxide 1,3-dipolar cycloaddition" --- p.15 / Chapter 1.3.a. --- Nitrone-olefin cycloaddition --- p.16 / Chapter 1.3.b. --- Nitrile-oxide-olefin cycloaddition --- p.17 / Chapter 1.4 --- Isoxazoline Transformation --- p.18 / Chapter Chapter 2 --- Results and Discussion / Chapter 2.1 --- General Aspect --- p.19 / Chapter 2.2 --- "Entries to 6 and 7-membered O-heterocycles via 1,3-dipolar nitrone cycloaddition" --- p.21 / Chapter 2.3 --- "Entries to 6 and 7-membered O-heterocycles via l,，3-diploar nitrile oxide cycloaddition" --- p.33 / Chapter 2.4 --- Conclusion --- p.47 / Chapter Chapter 3 --- Experimental / General --- p.49 / Experimental --- p.51 / References --- p.75