- Title
- Cyclodepsipeptides from a Kenyan marine cyanobacterium
- Creator
- Dzeha, Thomas Mwambire
- ThesisAdvisor
- Davies-Coleman, Mike
- Subject
- Cyanobacteria
- Subject
- Stereochemistry
- Subject
- Natural products -- Kenya
- Date
- 2003
- Type
- Thesis
- Type
- Masters
- Type
- MSc
- Identifier
- vital:4303
- Identifier
- http://hdl.handle.net/10962/d1004961
- Identifier
- Cyanobacteria
- Identifier
- Stereochemistry
- Identifier
- Natural products -- Kenya
- Description
- An examination of an organic extract of the cyanobacterium Lyngbya majuscula collected from Wasini Island off the southern Kenyan coast led to the isolation of the known cyclodepsipeptide antanapeptin A (7), recently isolated from a Madagascan collection of L. majuscula, and a new bioactive cyclodepsipeptide, homodolastatin 16 (42). Although L. majuscula is a common, pantropical cyanobacterium this study represents the first investigation of the natural product chemistry of a Kenyan population of L. majuscula. The structures of the two cyclodepsipeptides were determined from 2D NMR and mass spectrometry data. The L- stereochemistry of the proline, valine, and N-methylphenylalanine amino acids in 7 and the L – proline configuration in 42, was confirmed by Marfey’s HPLC method. Chiral GC was used to determine the absolute stereochemistry of the hydroxyisovaleric acid moiety in 7 and 42, the lactate residue in 42 and tentatively propose an L-stereochemistry for the Nmethylisoleucine amino acid in 42. Homodolastatin 16, a higher homologue of the potential anti-cancer agent, dolastatin 16, exhibited moderate activity against two oesophageal cancer cell lines.
- Format
- 108 p., pdf
- Publisher
- Rhodes University, Faculty of Science, Chemistry
- Language
- English
- Rights
- Dzeha, Thomas Mwambire
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