Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (Ph. D.)--University of Bern. / Cover title: Japanese Lac--Ki-urushi. Includes bibliographical references.

No description available.

Ph.D. / This chemotaxonomic study of the leaf phenolic compounds in the genus Aloe is introduced by presenting a review of Aloe taxonomy, followed by a second review of all known leaf compounds. A chemotaxonomic study of virtually all species of Aloe has made it possible to define several chemical groups in the genus of 420 species. The chemical groups are either identified by a single marker compound or by a series of unique compounds. The following groups have been identified and the chemotaxonomic value of each group is discussed: • An aloin / aloinoside / microdontin group, comprising 36 species, mostly of tropical origin. This group includes species not previously associated with one another. • An 8-O-methyl-7-hydroxyaloin group. Here the co-occurrence of some leaf compounds suggests that 8-O-methyl-7-hydroxyaloin is not homologous in the 18 species where it has been detected. Evidence is presented illustrating that 8-O-methyl-7-hydroxyaloin is an 'hybrid compound' which forms when two chemically divergent species (aloin- and homonataloincontaining parents) are crossed. • An aloenin group, comprising 16 species which are believed to be a monophyletic group. • A microstigmin group, indicating a taxonomic alliance between series Purpurascentes and series Anguialoe, with A. broomii an intermediate between the two. • A 10-hydroxyaloin B group, represented by series Asperifoliae and related species, which appears to be a drought adapted Glade of tropical origin. • A homonataloside group, comprising 14 species, suggesting a biochemical link between the aloes of north Africa and southern Africa. • An aloeresin E and F group, indicating a taxonomic alignment between series Mitriformes and five anomalous species. • A plicataloside group, with its single marker compound indicating a taxonomic relationship between 20 mostly tropical east African species. • A flavone group. The large number of species with flavones (sections Leptoaloe Graminialoe, Lomatophyllum and series Macrifoliae) are suggested to be basal in the genus. • A flavanone group. A few anomalous species produce flavanones but it is unlikely that they form a monophyletic group. A concluding review of leaf exudate compounds (not mentioned above) is also presented which includes hypotheses on the chemotaxonomic value of chromones and anthrones in general. A chemical re-arrangement of species is presented in the form of a new 'chemical classification' for Aloe based on chemotypes. These chemical groups have lead to an improved understanding of natural relationships in a genus where no satisfactory infrageneric classification has hitherto been available.

Plants are an invaluable source of medicinal compounds and their use for healing is rooted in ancient times. Aptosimum procumbens (Scrophulariaceae) and Garuleum bipinnatum (Asteraceae) are two indigenous South African plants that have been used as traditional remedies. Phytochemical investigations were performed with the aim of isolating and identifying compounds that may be responsible for the recorded medicinal properties of these plants. Various chromatographic techniques were utilized for the separation of the plant extract constituents. Several terpenoid compounds were isolated from both plants and the flavanone was isolated from A. procumbens. Nuclear magnetic resonance spectroscopy including 1H NMR, 13C NMR, COSY, DEPT, HMQC, HSCQ, HMBC and NOESY experiments were performed to allow for structure determination, the results of which will be discussed. The iridoid glycosides angeloside, shanzhiside methyl ester, barlerin, a new compound foliamethoylshanzhiside methyl ester and the flavanone pinocembrin neohesperidoside were identified as constituents of A. procumbens. Fractionation of the G. bipinnatum extract afforded several sandaracopimar-15-ene diterpenoid derivatives, namely sandaracopimar-15-ene-8ƒÒ-ol, sandaracopimar-15-ene-8ƒÒ,11ƒÑ-diol, 12-O-acetylsandaracopimar-15-ene-8ƒÒ,11ƒÑ,12ƒÒƒn-triol, 11-O-acetylsandara-copimar-15-ene-8ƒÒ,11ƒÑ,12ƒÒƒn-triol, 11-O- feruoylsandaracopimar-15-ene-8ƒÒ,11ƒÑƒz12ƒÒ-triol and 11-O-p-coumaroylsandaracopimar-15-ene-8,11ƒÑ,12ƒÒ-triol. Diterpenoids are known to possess antimicrobial properties enabling them to fight off various infections and monoterpenoid iridoid glycosides generally have anti-inflammatory properties that make them wound-healing agents. Flavonoids are a diverse group of compounds with enormous structural variations and have a wide range of medicinal properties. A general review on the structural classification, biosynthesis and biological activity of these secondary metabolites is given in this dissertation. Iridoids are commonly found in plants belonging to the Scrophulariaceae family and shanzhiside methyl ester has also been isolated from A. indivisum, a related Aptosimum species. Many plants from the Scrophulariaceae family have been used as traditional medicine to treat wounds. The crude extract of the plant tested positive for antitumor activity against three cell lines, namely melanoma, breast and renal. G. bippinatum belongs to one of the largest plant families, Asteraceae and the crude extract exhibited antimicrobial activity against several microorganisms. / Prof. F.R. van Heerden

Weakening of fruit and petal abscission zones in Rubus idaeus L. cv. Glen Clova was accompanied by increased rates of ethylene production. Both processes were accelerated by a supply of exogenous ethylene. In the ripe fruit natural ethylene levels were saturating. The rise in ethylene production clearly preceded petal abscission but in fruit the increase virtually coincided with the start of weakening. Raspberry fruit of other varieties and blackberries clearly showed the abscission zone weakening could precede any increase in ethylene production. The internal ethylene concentrations of Glen Clova fruit at the mottled stage reached those levels which had to be added to stimulate abscission (ie 0.25 to 0.5 ppm). This is the very stage at which abscission zone weakening was first noticeable. Both fruit and petal abscission was retarded by the application of inhibitors of ethylene production ( AVG, Co 2+) or action (Ag+ ). Likewise a reduction in the internal ethylene under hypobaric pressure also retarded fruit abscission. None of these treatments were totally capable of preventing abscission. In fruit abscission the receptacle appears to have an important role. The increase in receptacle ethylene production precedes that of the drupelets. The enlargement and swelling of the receptacle tissues are important in both abscission zone weakening and ethylene production. This receptacle development may in turn be controlled by the development of fertilised drupelets. The ethylene production in both fruit and petal abscission is limited initially by the supply of ACC. In both cases endogenous ACC levels increase in step with ethylene production. Ethylene's role as a coordinating/accelerating agent in fruit and petal abscission is discussed.

The gas exchange responses of two cultivars of Hordeum vulgare L., to light, temperature, CO₂ and water stress were investigated in the laboratory. The optimum temperature for net CO₂ assimilation was found to be 25°C and 22.5°C for cv. Clipper and cv. Dayan respectively. Net CO₂ assimilation was reduced at 30°C in cv. Dayan. At low light intensity the highest quantum yield efficiency was 0.051 mol.mol⁻¹ at 30°C for cv. Clipper, and 0.066 mol.mol⁻¹ at 20°C for cv. Dayan. At the same temperature, cv. Clipper had a higher water use efficiency than cv. Dayan, but stomatal conductance for cv. Dayan was higher than cv. Clipper. Stomatal limitation to CO₂ was lowest at the optimum temperature for CO₂ assimilation in both cultivars. Stomata limited CO₂ assimilation in cv. Clipper to a larger degree than in cv. Dayan. Relative stomatal limitation for cv. Clipper at 25°C was 0.280 ± 0.010, and for cv. Dayan at 22.5°C was 0.028 ± 0.011. Short-term exposure to elevated CO₂ concentrations increased CO₂ assimilation in both cultivars, but more so for cv. Clipper. Transpiration rate at elevated CO₂ partial pressures were higher in cv. Dayan than in cv. Clipper. At very high CO₂ (860 μmol.m⁻²s⁻¹) partial pressure water use efficiency in cv. Clipper was higher than cv. Dayan, but at low CO₂ partial pressures water use efficiency in cv. Dayan was higher than cv. Clipper. Water stress reduced the relative leaf water content and net CO₂ assimilation in both cultivars. Cultivar Dayan was more tolerant to water stress, and CO₂ assimilation in this cultivar was less affected by water stress. In both cultivars water stress increased the concentration of chlorophyll a, chlorophyll b, and chlorophyll a+b. The chlorophyll a:b ratio remained relatively constant throughout the stress period. No correlation between relative leaf water content and total carotenoid concentration was observed.

M.Sc. / Pentanisia prunelloides belongs to the Rubiaceae family and is distributed in the grasslands of the eastern part of Southern Africa. The plant is an erect perennial herb that grows to be approximately 30 cm in height. It has stout hairy stems sprouting from a tuberous root. This plant produces pale purple flowers in early summer. P. prunelloides extracts are used in traditional medicine for a wide range of ailments such as colds, rheumatism, heartburn and sores. It is also incorporated in many multipurpose traditional medicines. The raw tuber is occasionally chewed to relief heartburn. The root decoctions were reported to have been used in the 1918 influenza pandemic with great success. The use of this plant in ethno-medicine suggests that it has bio-active principles which justify its continued use by different generations. It has shown to have anti-inflammatory, anti-viral and antibacterial properties. As far as the chemical composition is concerned, only palmitic acid was previously isolated. This compound can not account for all the chemotherapeutic properties of P. prunelloides. Thus this study was done to investigate the chemical constituents of P. prunelloides which may be responsible for its use as a medicinal plant. The plant material was collected from different areas in Swaziland and South Africa. Chemical variation screening was conducted using ether/hexane, methanol and boiling water extracts of the tuber and where possible the aerial parts of P. prunelloides. The methanol extracts were the only extracts used for TLC screening and the results showed the presence of terpenoids, saponins, amino acids, carbohydrates and phenolic compounds that were not identified previously. An attempt was made to quantify some of the compounds by means of HPLC and GC/MS. The compounds observed from all the tuber experiments demonstrated a limited level of variation both in quality and quantity within and between natural plant populations. The variation was found to be random and it was not correlated to the geographical distribution of this plant. This was concluded because variation was observed in plants which were from the same locality as well as different localities. iv The chemotypes observed between the tubers from Swaziland and South Africa were related. This means that there was no unique chemotype observed from plants from the two countries as chemotypes overlap. When considering the TLC of medium polarity compound and polar compounds of the aerial parts, three chemotypes were observed. Again these chemotypes were observed within and between natural plant populations. The occurrence of these chemotypes was random and was not correlated to the geographic distribution of the plants. The variations observed could be due to different developmental stages of the plants. The chemistry of P. angustifolia was also investigated and compared to that of P. prunelloides. This was done because these two species are used to treat the same ailments and could be physiologically mistaken for each other. It was established that the two species could be differentiated based on TLC as the two species contain different compounds. The methanol extract was used to isolate three of the major compounds from P. prunelloides. The compounds had different polarities with one compound being non-polar, another having medium polarity and the third one being polar. The structure of the compound with medium polarity was identified to be (–)-epicatechin, a flavanol, while the polar compound was sucrose. The structure of the non-polar compound could not be concluded due to the complex nature of this compound, but it was assumed to be a triterpenoid, or two stereoisomers of the same compound. The methanol extract was also fractionated to get three fractions which were non-polar, medium polar and polar extracts (containing the three isolated compounds respectively). These extracts together with the crude extract were subjected to antibacterial screening. Bioautographic tests did not show any specific zones from the separated compounds to have any significant antibacterial activity. However, the total extract and the non-polar fraction showed the highest activity with the non-polar fraction recording MIC values of not more than 1.25 mg/cm3. It was then assumed that the compounds from P. prunelloides worked additively or in synergy to produce the observed activity. In future more detailed chemical variation studies need to be done to investigate more specific factors such as soil type, age of the plant and seasonal variation. This would give better indications of when the plant has more of the active compounds thus giving a guide about the best harvesting time. Anti-inflammatory and anti-oxidant tests may also prove to be interesting.

The isolation and identification of pyrrolizidine alkaloids from various plant species from 1988 to May 1991 are reviewed and the alkaloids of two indigenous plant species, Senecio speciosus Willd and Senecio macrocephalus DC, were investigated. A brief review of the methods used for isolation and identification of pyrrolizidines is also given. S. speciosus was found to contain two new alkaloids, 7-senecioyl-9-sarracinylheliotridine and 7-isosarracinyl-9- sarracinyl-heliotridine, which were identified using highfield NMR techniques. A number of other alkaloids were tentatively identified using GC-MS. S. macrocephalus contains very little alkaloid, but a number of pyrrolizidine alkaloids were tentatively identified using GC-MS. Standard alkaloids for GC-MS work were obtained both by extraction from a number of plant species and by synthesis of simple monoester alkaloids. In this process the alkaloid neosarracine, previously described by GC-MS, was isolated and NMR data for this compound are reported for the first time. S. speciosus and S. macrocephalus are morphologically very similar and their counterparts in the Grahamstown district exhibit features characteristic of both species. This could be due to hybridization, genetic mutation or simple variation within the species. The alkaloids of four local plant populations were examined in order to collect taxonomic markers whereby it was hoped that the Grahamstown plants could be satisfactorily classified. Three of the plant populations were found to contain 7-senecioyl-9-sarracinylheliotridine and 7-angelyl-9-sarracinyl-heliotridine. One population was found to contain the known alkaloid retrorsine along with the new alkaloid 2-hydroxy-l, 2-dihydrosenkirkine. The alkaloidal fractions of all four populations were compared using GC-MS and NMR techniques. Tentative taxonomic conclusions were drawn.

The isolation and structure determination of dubiin and leonitin, two new diterpenoid acetates from Leonotis dubia and Leonotis leonitis respectively, are discussed. The compounds are diterpenoids of the labdane type and are closely related to marrubiin. The proposed structures are based on chemical and spectral evidence. Dubiin, C₂₂H₃₀0₆̕ contains a tertiary hydroxy- group, a furan ring and a ó-lactone while leonitin, C₂₂H₃₀0₇̕ is a γ - dilactone. at C-20. Both compounds are unusual in being oxygenated The extraction of three Euryops species and the isolation of euryopsol, C₂₂H₃₀0₄̕̕ are also described. A furanoeremophilane structure containing three hydroxy- groups, one of which is at a bridgehead position, is proposed. Euryopsol is the first furanoeremophilanoid with a substituent attached at C-IO