[1] Univ St Andrews, Sch Biol, Biomed Sci Res Complex, St Andrews KY16 9ST, Fife, Scotland
[2] Univ Cape Town, Drug Discovery & Dev Ctr H3D, ZA-7701 Rondebosch, South Africa
[3] Univ Cape Town, South African Med Res Council, Drug Discovery & Dev Res Unit, Dept Chem, ZA-7701 Rondebosch, South Africa
[4] Univ Cape Town, Inst Infect Dis & Mol Med, ZA-7701 Rondebosch, South Africa
[5] Univ St Andrews, Sch Chem, St Andrews, Fife, Scotland
[6] Univ Aberdeen, Dept Chem, Marine Biodiscovery Ctr, Old Aberdeen AB24 3DT, Scotland
[7] NCI, Nat Prod Branch, Frederick Natl Lab, NIH, Bethesda, MD 20892 USA
[8] Rhodes Univ, Dept Biochem & Microbiol, Grahamstown, South Africa