Browsing by Author "Davies-Coleman, Michael T"

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    Anti-oesophageal cancer activity in extracts of deep-water Marion Island sponges
    (2005) Davies-Coleman, Michael T; Froneman, William; Keyzers, Robert; Whibley, Catherine; Hendricks, Denver; Samaai, Toufiek; McQuaid, Christopher
    OESOPHAGEAL CANCER IS ONE OF THE most common causes of cancer-related deaths in South African black males. The limited efficacy of chemotherapeutic agents to treat this disease has prompted a search for potential new chemical entities with anticancer properties. We report here on the evidence for anti-oesophageal cancer activity in the methanolic extracts of five species of sponges dredged from a depth of approximately 100 m in the vicinity of Marion Island in the Southern Ocean during the autumn of 2004.
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    South African marine compounds as anticancer agents
    (2006) Whibley, Catherine Evelyn; Hendricks, Denver T; Davies-Coleman, Michael T
    Oesophageal cancer is the most common cause of cancer related deaths among black males in South Africa. Currently there are very limited treatment options, and patients have a very poor prognosis, due in part to the late stage at which this cancer is usually detected. In this thesis we describe the establishment of a screening assay using an oesophageal cancer cell line as a model. It was our hope that this screen would allow us to identify compounds which have activity against oesophageal cancer, that could be used as lead agents for further development of chemotherapeutic agents. Once our screen was established, we tested a wide range of extracts from southern African marine organisms, supplied by our collaborators from Rhodes University, South Africa. The marine environment represents a rich, untapped repository of novel and interesting compounds, and through our collaboration we had access to a wide range of marine-derived extracts and compounds. During the course of this project we provided screening data to assist in activity-directed fractionation from five active marine extracts, giving rise to 15 compounds of varying activity. These included several groups of novel active compounds such as the makaluvic acids from the sponge Strongylodesma aliwaliensis and the malonganenones from the octocoral Leptogorgia gi/christii. The identification of a number of novel, active compounds through our screening program highlights the potential of marine organisms from the southern African coast as a source of novel drug leads.
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    The X-ray crystal structures of ambraketal and 8-epi-ambraketal
    (Science Reviews 2000 Ltd, 2003) Gray, Christopher A; Davies-Coleman, Michael T; Caira, Mino R; Nathansona, Carole A; Wisch, Gregory A
    The crystal structures of ambraketal and 8-epi-ambraketal, synthesised in five steps from (–)-sclareol, are reported. Ambergris, a concretion formed in the intestinal tract of the blue sperm whale, has been used by perfumers since ancient times because of its unique fragrance and fixative properties.1 Restrictions imposed upon the whaling industry, in an attempt to protect these endangered marine mammals, have forced chemists to make synthetic substitutes for ambergris. Among these synthetic substitutes, the two epimeric bisnorlabdane acetals ambraketal (1; amberketal, ambracetal) and 8-epiambraketal (2, epi-amberketal, 8-epi-ambracetal, isoambraketal) have found prominence due to their strong fragrance and fixative properties respectively. Compounds 1 and 2 have also been reported as minor constituents in the bark of the western white pine tree (Pinus monticola).2