Cyclodepsipeptides from a Kenyan marine cyanobacterium

Dzeha, Thomas Mwambire (2002) Cyclodepsipeptides from a Kenyan marine cyanobacterium. Masters thesis, Rhodes University.




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.

Item Type:Thesis (Masters)
Uncontrolled Keywords:Cyanobacteria, Stereochemistry, Natural products, Kenya
Subjects:Q Science > QD Chemistry > QD241 Organic chemistry
Divisions:Faculty > Faculty of Science > Chemistry
ID Code:2226
Deposited By: Ms Chantel Clack
Deposited On:23 Nov 2011 08:19
Last Modified:06 Jan 2012 16:22
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