Ph.D. / Cussonia Thunb. is a genus of 21 species (including one that is currently undescribed) found in grasslands, woodlands and forests of sub- Saharan Africa, the Arabian Peninsula (Yemen) and the Comoro Islands. The genus generally has soft brittle branches, a fleshy underground tuber and fleshy roots. Despite these features, Cussonia is not found in the dry and arid regions of Africa. They are generally trees or shrubs, and less often lianes (C. thyrsiflora Thunb.) or suffrutices (C. corbisieri De Wild.). The tree forms usually grow between 4 to 20 m in height; however C. zimmermannii Harms can grow up to 45 m tall. Cussonia corbisieri has a large woody underground caudex with multiple 1 m tall, herbaceous stems. Probably the most distinguishing feature of this genus is the shape and size of the leaves. The palmately compound leaves are carried (in most cases) on the ends of the branches. The simple palmatisect leaves, such as in C. arborea Hochst. ex A.Rich. or C. natalensis Sond., are not subdivided into smaller leaflets, while the compound leaves increase in complexity from mono-palmately compound to multi-palmately compound. The multi-palmate compound leaves are carried on long petioles (up to 700 mm) having up to nine leaflets (up to 500 mm long), with each leaflet having two or more articulations bearing secondary leaflets (up to 400 mm long). These secondary leaflets can be subdivided into tertiary leaflets (up to 200 mm long).

Cussonia species (commonly known as Cabbage trees) are indigenous to South Africa and are used in traditional medicine to treat an assortment of diseases. Due to their attractive growth form, they are assets in gardens. However, there are no developed methods for propagating these species. The use of three selected species, Cussonia paniculata (Eckl. & Zeyh.), C. spicata (Thunb.) and Schefflera umbellifera (Sond.) Baill, = C. umbellifera), in traditional medicine was validated. Rapid propagation protocols for C. paniculata and C. spicata were investigated and ultimately developed for the former species. Cussonia paniculata, C. spicata and C. umbellifera were screened for their medicinal properties, mainly focussing on anti-bacterial, anti-inflammatory and anti-malarial activities. In the anti-bacterial screening, C. spicata bark and root extracts showed activity against selected Gram-positive and Gram-negative bacterial strains at a concentration of 50 mg ml ¯¹ . The highest inhibition was observed with ethanol and ethyl acetate root extracts against Staphylococcus aureus. The other two species did not show anti-bacterial activity. Ethanol and ethyl acetate extracts of all species showed anti-inflammatory activity in the cyclooxygenase assay (COX-1) at a concentration of 8 μg ml ¯¹, These active extracts showed an inhibition percentage that was greater than 50 % against cyclooxygenase. In the anti-malarial screening , bark extracts were screened. C. umbellifera bark extracts exhibited the best inhibition against P. falciparum, a malaria-causing agent in humans. The percentage inhibition of these extracts was up to 100% at a concentration of 200 μg ml ¯¹ . While C. spicata is known to be used to treat malaria, the screening results showed much less activity (less than or equal to 35 %) as compared to C. umbellifera, which is preferably used to treat malaria. The results obtained from screening these three species validated their use in traditional medicine. This means that the people or traditional healers use these species for different treatments by possibly relying on past knowledge about the effects after administering the medicine. Fingerprinting using Thin Layer Chromatography (TLC) was used in an attempt to determine whether there are any chemical differences or similarities between the three species. There were similarities between the plant parts across the species as well as some differences. However, this method cannot be used as an unequivocal test to deduce that compounds that are present in a certain species and not in others are the ones responsible for bringing about a certain biological activity. That can only be achieved by a bioassay-guided isolation of possible compounds. A tissue culture protocol was developed to produce a large -number of plants of C. paniculata. Explants were derived from nodal explants of in vitro germinated seeds and cultured on Murashige and Skoog (MS) (1962) medium supplemented with 3% sucrose, 2.5 mg l ¯¹ BA and solidified with 3 g l ¯¹ Gelrite. These explants produced multiple shoots. The average number of shoots per explant ranged between 1 to 3.5. Multishoots were subcultured on to rooting media and roots were produced on MS with 0.75 mg l ¯¹ IBA and 1 mg l ¯¹ NAA. Callus from zygotic embryos also produced plantlets on MS supplemented with 1.5 mg l ¯¹ 2,4-D and 0.5 mg l ¯¹ BA. Hyperhydricity was encountered in this study. This problem was reversed successfully by transferring the shoots from medium solidified with 3 g l ¯¹ Gelrite to medium solidified with 8 g l ¯¹ agar. Plantlets were successfully acclimatized for planting ex vitro. The percentage of healthy plants after a 35-day acclimatization period was 63 %. C. spicata was not successfully micropropagated from shoot-tip explants. However, a protocol was developed for decontaminating shoot-tips from the mother plants. The plant material was successfully decontaminated with 0.01% HgCl₂ for 15 min. The decontamination percentage was up to 80 %. Browning of the explants was observed and it was successfully treated with soaking the explants in a 15 mg l ¯¹ ascorbic acid solution for 15 min. A high percentage of shoot-tip regeneration (80 %) was observed when they were cultured on MS medium supplemented with 2 mg l ¯¹ BA, 1 mg l ¯¹ IAA and 1 mg l ¯¹ GA₃. However, multishoots were not observed as in C. panicualata. Shoot elongation in vitro was similar to shoot elongation as it occurs in nature. The shoots elongated and a flush of palmitately arranged leaves were produced. Further research is required to investigate a commercially viable protocol for rapid propagation and conservation of the germplasm of Cussonia species. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

L’intérêt des substances d’origine naturelle, potentiellement anti-tumorales nous a amené à nous intéresser aux saponines triterpéniques et stéroïdiques de plantes issues de la biodiversité africaine de la famille des Araliaceae et des Dracaenaceae. En effet, des études antérieures menées sur quelques plantes de ces deux familles ont conduit à l’obtention de molécules complexes et originales possédant d’excellentes propriétés cytotoxiques, immuno-modulatrices, anti-inflammatoires. Au vu de ces résultats nous avons entrepris des investigations pharmaco-chimiques sur Cussonia arborea (Araliaceae), Dracaena deisteliana et Dracaena arborea (Dracaenaceae), plantes médicinales couramment utilisées en pharmacopée traditionnelle africaine pour traiter différentes maladies. Les travaux menés ont conduit à l’isolement de 31 composés purs en utilisant les différentes techniques analytiques du laboratoire notamment les diverses techniques de chromatographie liquide successive à pression atmosphérique, moyenne pression et flash chromatographie sur silice en phase normale et en phase inverse. Les structures ont été déterminées par les méthodes de spectrométrie de masse en source FAB et de spectroscopie de RMN 1D et 2D (COSY, TOCSY, NOESY, HMBC et HSQC). Parmi les 07 composés purs obtenus des écorces de Cussonia arborea, 5 sont des nouvelles saponines triterpéniques dont un dérivé de l’acide ursolique, un dérivé de l’hédéragénine et trois dérivés de l’acide oléanolique, tous disubstitués en position 3 et 28 par des chaînes oligosaccharidiques. 13 composés purs sont obtenus à partir des feuilles de Cussonia arborea, dont 7 nouvelles saponines triterpéniques dérivés de l’acide ursolique, de l’acide 23-hydroxyursolique, de l’hédéragénine et de l’acide oléanolique dont 04 d’entre elles sont obtenues sous forme de mélanges inséparables d’isomères acide oléanolique/acide ursolique et hédéragénine/acide 23-hydroxyursolique. A partir des écorces de Dracaena arborea et des tiges de Dracaena deisteliana, nous avons isolé et caractérisé 10 saponines stéroïdiques dont 4 nouvelles et une sapogénine. Les activités de certains de ces produits purs ont été évaluées sur deux lignées de cellules cancéreuses coliques humaines HCT 116 et HT-29. / The interest of the substances from natural origin, potentially antitumor led us to interest in triterpenoid and steroidal saponins of plants from the African biodiversity belonging to the Araliaceae and Dracaenaceae families of plants. Indeed, of the former studies undertaken on some plants of these two families led to obtaining complex and original molecules having excellent cytotoxic, immuno-modulating, anti-inflammatory properties. Within sight of these results we undertook pharmaco-chemical investigations on Cussonia arborea (Araliaceae), Dracaena deisteliana, and Dracaena arborea (Dracaenaceae), medicinal plants usually used in african traditional pharmacopeia to treat various diseases. The work led to the isolation of 31 pure compounds by using the various analytical techniques in particular the various chromatography techniques (CC, MPLC, TLC, flash) on silica gel, normal and reversed phases. The structures were determined by the methods of mass spectrometry (FAB, ESI, IE) and 1D (1H and 13C) and 2D (COSY, TOCSY, NOESY, HMBC and HSQC) NMR spectroscopy. Among the 07 pure compounds obtained of the barks of Cussonia arborea, 5 are new triterpenoid saponins derivatives of ursolic acid, hederagenin and three derived from the acid oleanolic, all disubstituted in position 3 and 28 by oligosaccharidic chains. 13 pure compounds were obtained from leaves of Cussonia arborea, seven of which are new triterpenoid saponins derivatives of oleanolic acid, ursolic acid, hederagenin and 23-hydroxyursolic acid of which four were obtained as mixtures of isomers oleanolic acid/ursolic acid and hederagenin/23-hydroxyursolic acid. From the bark of Dracaena arborea and stem of Dracaena deisteliana, we isolated and characterized ten steroidal saponins including 4 new and sapogenin. The activities of some of these pure products were evaluated on two cancerous lines human colic cells HCT 116 and HT-29.

L'intérêt des substances d'origine naturelle, potentiellement anti-tumorales nous a amené à nous intéresser aux saponines triterpéniques et stéroïdiques de plantes issues de la biodiversité africaine de la famille des Araliaceae et des Dracaenaceae. En effet, des études antérieures menées sur quelques plantes de ces deux familles ont conduit à l'obtention de molécules complexes et originales possédant d'excellentes propriétés cytotoxiques, immuno-modulatrices, anti-inflammatoires. Au vu de ces résultats nous avons entrepris des investigations pharmaco-chimiques sur Cussonia arborea (Araliaceae), Dracaena deisteliana et Dracaena arborea (Dracaenaceae), plantes médicinales couramment utilisées en pharmacopée traditionnelle africaine pour traiter différentes maladies. Les travaux menés ont conduit à l'isolement de 31 composés purs en utilisant les différentes techniques analytiques du laboratoire notamment les diverses techniques de chromatographie liquide successive à pression atmosphérique, moyenne pression et flash chromatographie sur silice en phase normale et en phase inverse. Les structures ont été déterminées par les méthodes de spectrométrie de masse en source FAB et de spectroscopie de RMN 1D et 2D (COSY, TOCSY, NOESY, HMBC et HSQC). Parmi les 07 composés purs obtenus des écorces de Cussonia arborea, 5 sont des nouvelles saponines triterpéniques dont un dérivé de l'acide ursolique, un dérivé de l'hédéragénine et trois dérivés de l'acide oléanolique, tous disubstitués en position 3 et 28 par des chaînes oligosaccharidiques. 13 composés purs sont obtenus à partir des feuilles de Cussonia arborea, dont 7 nouvelles saponines triterpéniques dérivés de l'acide ursolique, de l'acide 23-hydroxyursolique, de l'hédéragénine et de l'acide oléanolique dont 04 d'entre elles sont obtenues sous forme de mélanges inséparables d'isomères acide oléanolique/acide ursolique et hédéragénine/acide 23-hydroxyursolique. A partir des écorces de Dracaena arborea et des tiges de Dracaena deisteliana, nous avons isolé et caractérisé 10 saponines stéroïdiques dont 4 nouvelles et une sapogénine. Les activités de certains de ces produits purs ont été évaluées sur deux lignées de cellules cancéreuses coliques humaines HCT 116 et HT-29.