Nocardichelins A and B, siderophores from Nocardia strain Acta 3026

An actinomycete, strain Acta 3026, isolated from mangrove soil was characterized and found to belong to the genus Nocardia. The strain produces two new cytotoxic metabolites, nocardichelins A (1) and B (2). Each of the compounds strongly inhibited human cell lines from gastric adenocarcinoma, breast carcinoma, and hepatocellular carcinoma with GI(50) values in a low micromolar to nanomolar range. The structural characterization of the compounds was performed by mass spectrometry and NMR spectroscopy. The nocardichelins represent a new group of siderophores that combine the structural elements of mycobactin-type siderophores from mycobacteria and hydroxamate-type siderophores (desferrioxamine B) produced by streptomycetes. The chromazurol S assay, characteristic for iron(III) complexation, was positive, confirming the role as a siderophore

Atacamycins A-C, 22-membered antitumor macrolactones produced by Streptomyces sp C38

Three new 22-membered macrolactone antibiotics, atacamycins A-C, were produced by Streptomyces sp. C38, a strain isolated from a hyper-arid soil collected from the Atacama Desert in the north of Chile. The metabolites were discovered in our HPLC-diode array screening and isolated from the mycelium by extraction and chromatographic purification steps. The structures were determined by mass spectrometry and NMR experiments. Atacamycins A, B and C exhibited moderate inhibitory activities against the enzyme phosphodiesterase (PDE-4B2), whereas atacamycin A showed a moderate antiproliferative activity against adeno carcinoma and breast carcinoma cells. The Journal of Antibiotics (2011) 64, 775-780; doi: 10.1038/ja.2011.96; published online 19 October 201