3 research outputs found
Polypropionates from the South African Marine Mollusk <i>Siphonaria oculus</i>
Three new polypropionate metabolites, 6<i>Z</i>,8<i>E</i>-Δ<sup>8</sup>-siphonarienfuranone (<b>1</b>), 6<i>E</i>,8<i>E</i>-Δ<sup>8</sup>-siphonarienfuranone (<b>2</b>), and 6<i>E</i>,8<i>E</i>-3-hydroxy-4,6,8,10,12-pentamethylpentadeca-6,8-dien-5-one
(<b>3</b>), and the known polypropionate siphonarienfuranone
(<b>4</b>) were isolated from the intertidal South African marine
mollusk <i>Siphonaria oculus</i>. Evidence is presented
to suggest that <b>1</b>, <b>2</b>, and <b>4</b> may cyclize from an acylic precursor on chromatographic workup of
the acetone extract of this mollusk
Antimicrobial Rubrolides from a South African Species of <i>Synoicum</i> Tunicate
The CH<sub>2</sub>Cl<sub>2</sub>–MeOH extract
of a South
African tunicate described as the new <i>Synoicum globosum</i> Parker-Nance sp. nov. (Ascidiacea, Aplousobranchia) was subjected
to <sup>1</sup>H NMR-guided fractionation. This resulted in the identification
of new 3″-bromorubrolide F (<b>1</b>), 3′-bromorubrolide
E (<b>2</b>), 3′-bromorubrolide F (<b>3</b>), and
3′,3″-dibromorubrolide E (<b>4</b>) and reisolation
of known rubrolides E (<b>5</b>) and F (<b>6</b>), based
on NMR spectroscopic and mass spectrometric data. Biological testing
of both new and known members of this reported antimicrobial family
of halogenated, aryl-substituted furanones indicated moderate antibacterial
properties for 3′-bromorubrolide E (<b>2</b>), 3′,3″-dibromorubrolide
E (<b>4</b>), and rubrolide F (<b>6</b>) against methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) and <i>S. epidermidis</i>
Mandelalides A–D, Cytotoxic Macrolides from a New <i>Lissoclinum</i> Species of South African Tunicate
Mandelalides A–D are variously glycosylated, unusual
polyketide
macrolides isolated from a new species of <i>Lissoclinum</i> ascidian collected from South Africa, Algoa Bay near Port Elizabeth
and the surrounding Nelson Mandela Metropole. Their planar structures
were elucidated on submilligram samples by comprehensive analysis
of 1D and 2D NMR data, supported by mass spectrometry. The assignment
of relative configuration was accomplished by consideration of homonuclear
and heteronuclear coupling constants in tandem with ROESY data. The
absolute configuration was assigned for mandelalide A after chiral
GC-MS analysis of the hydrolyzed monosaccharide (2-<i>O</i>-methyl-α-l-rhamnose) and consideration of ROESY correlations
between the monosaccharide and aglycone in the intact natural product.
The resultant absolute configuration of the mandelalide A macrolide
was extrapolated to propose the absolute configurations of mandelalides
B–D. Remarkably, mandelalide B contained the C-4′ epimeric
2-<i>O</i>-methyl-6-dehydro-α-l-talose. Mandelalides
A and B showed potent cytotoxicity to human NCI-H460 lung cancer cells
(IC<sub>50</sub>, 12 and 44 nM, respectively) and mouse Neuro-2A neuroblastoma
cells (IC<sub>50</sub>, 29 and 84 nM, respectively)