3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Senecio serratuloides var. in wound healing: efficacy and mechanistic investigations in a porcine wound model(2015-09-16) Gould, Alan NicolasSenecio serratuloides is widely used for wound healing in South Africa but minimal information regarding its efficacy is available. Furthermore toxic pyrrolizidine alkaloids may be present. The following investigation sought firstly to evaluate the efficacy and safety of Senecio serratuloides in a porcine wound model; secondly to assess for a potential mechanism and finally isolate and identify fractions in in-vitro assays. Assessment of Efficacy and Safety Materials and Methods: Deep partial thickness and full thickness wounds were created on 9 pigs. Treatment included an occlusive dressing (negative control), activated carbon, or the Senecio preparation. Wounds were monitored using photographic documentation, pH measurement and histological analysis (skin thickness and collagen content). Toxicity was monitored on blood and liver samples. Results and Discussion: Efficacy of Senecio serratuloides was established with a significantly thicker epidermis, maximal at day 7 post-operative, 2 days before the controls. Effects on collagen content was negligible with no toxicity detected. Mechanistic investigation Materials and Methods: Wound fluid was analysed for IL-10, IL-12, IL-1β, IL-6, IL-8, TNF-α using flow cytometry based assays. Tyrosine phosphorylation and cellular proliferation was assessed using dual immunofluorescence staining. Results and Discussion: IL-1β levels were significantly greater in the Senecio treatment. Tyrosine phosphorylation increased to day 9 post-operative where it stabilised in all groups. In the same period, cellular proliferation was sustained in the Senecio treated wounds but not in the controls. Keratinocyte proliferation was identified as the target for in-vitro assays. Extraction, Isolation and Partial Identification using In-vitro Proliferation Assays. Materials and Methods: The plant was fractionated using solid phase extraction cartridges. Keratinocytes were grown under standard conditions in 96-well plates. Cellular proliferation was assessed spectrophotometrically using a resazurin dye technique. Active fractions were analysed using gas chromatography and mass spectrometry. Results and Discussion: Identified fractions increased the rate of proliferation by 300- 400%. Potential lead compounds were identified. Importantly, pyrrolizidine alkaloids could not be detected. Conclusion Senecio serratuloides is efficacious in treating deep partial thickness wounds without inducing liver toxicity. Sustained keratinocyte proliferation linked to tyrosine phosphorylation may be an underlying mechanism. Although successful, in-vitro detection of active fractions requires further characterisation.Item Enaminones in the synthesis of azabicyclic models for alkaloids(2008-10-06T13:36:45Z) Mthembu, Siyanda ThabaniThe purpose of this project was to investigate whether methodology developed in these laboratories for preparing 5/6 and 6/6 azabicyclic systems with bridged head nitrogen can be extended to 7/6, 8/6, 9/6 and 13/6 azabicyclic systems. The methodology entails the use of enaminones as central to the formation of the azabicyclic systems. The synthetic route adopted began with the Beckmann rearrangement reaction and/or the Schmidt reaction of cyclic ketones to make lactams, which were then thionated by Curphy or Brillon procedures. The Michael reaction of NH thiolactams with tert-butyl acrylate was followed by Eschenmoser sulfide contraction to afford the enaminones 132 which were utilised in the ring-closing step. This involved hydrolysis of the tert-butyl ester and cyclisation via a mixed anhydride. Ethyl 7-oxo-1,2,3,5,6,7-hexahydroindolizine-8-carboxylate 170b, 1-(4- nitrobenzoyl)-3,4,6,7,8,9-hexahydroquinolizin-2-one 172a, 1-benzoyl- 3,4,7,8,9,10-hexahydropyrido[1,2-a]azepin-2(6H)-one 173d, 1-(4-nitrobenzoyl)- 3,4,6,7,8,9,10,11-octahydropyrido[1,2-a]azocin-2-one 174a, and 1-(4- nitrobenzoyl)-3,4,7,8,9,10,11,12,13,14,17,16-dodecahydropyrido[1,2-a]azacyclotridecin- 2(6H)-one 176a were synthesised in good yields, but yields of 8-(4- nitrobenzoyl)-2,3,5,6-tetrahydroindolizin-7(1H)-one 171a and 1-(4-nitrobenzoyl)- 3,4,7,8,9,10,11,12-octahydropyrido[1,2-a]azonin-2(6H)-one 175a were not satisfactory. In a much shorter synthetic route that involves enaminone chemistry as well, NH vinylogous amides were synthesised by the Eschenmoser sulfide contraction and used in the aza-annulation reaction with acryloyl chloride. Structural isomers (to compounds mentioned above) 8-(4-nitrobenzoyl)-2,3,6,7-tetrahydroindolizin- 5(1H)-one 178a, 1-(4-nitrobenzoyl)-2,3,7,8,9,10-hexahydropyrido[1,2-a]azepin- 4(6H)-one 180a, 1-benzoyl-2,3,7,8,9,10-hexahydropyrido[1,2-a]azepin-4(6H)-one 180b, 1-(4-nitrobenzoyl)-2,3,6,7,8,9,10,11-octahydropyrido[1,2-a]azocin-4-one 181a, 1-(4-nitrobenzoyl)-2,3,7,8,9,10,11,12-octahydropyrido[1,2-a]azonin-4(6H)- one 182a and 1-(4-nitrobenzoyl)-2,6,7,8,9,10,11,12,13,14,15,16- dodecahydropyrido[1,2-a]azacyclo-tridecin-4(3H)-one 183a were synthesised in good yields. 1-(4-Nitrobenzoyl)-2,3,6,7,8,9-hexahydroquinolizin-4-one 179a was obtained in low yield, and apparently as two conformational isomers.Item Models for the Diastereoselective Synthesis of Indolizidine Alkaloids:(2006-10-26T07:09:48Z) Krause, Rui Werner MaçedoThe synthesis of nitrogen containing ring systems has been one of the interests of this research group at the University of the Witwatersrand for a long time. These systems form part of a group of compounds called alkaloids, whose structural diversity is rivalled only by their distribution in nature. A small sub-set of the alkaloids is the fused 5 and 6 membered bicyclic frames with nitrogen at one bridgehead. Having developed a unique method of synthesising these indolizidine alkaloids, we examined various aspects of this methodology and there remained one crucial question – what is the best way to control the stereochemical outcome of the ring-forming steps? This project looks at this question from the view of a model natural product, the indolizidine alkaloids (+)- and (–)-tashiromine. The synthesis of tashiromine and related compounds was examined using chiral auxiliaries such as the Oppolzer sultam and the Evans oxazolidinone, as well as the use of chirally modified reductants. The efficacies of the chiral auxiliaries were studied using molecular modelling techniques, and certain modifications were suggested from these results.