Minutissamides E-L, antiproliferative cyclic lipodecapeptides from the cultured freshwater cyanobacterium cf. Anabaena sp.

The extract of UIC 10035, a strain obtained from a sample collected near the town of Homestead, South Florida, showed antiproliferative activity against MDA-MB-435 cells. Bioassay-guided fractionation led to the isolation of a series of cyclic lipodecapeptides, named minutissamides E–L (1–8). The planar structures were determined by analysis of HRESIMS, tandem MS, and 1D and 2D NMR data, and the stereoconfigurations were assigned by LC–MS analysis of the Marfey’s derivatives after acid hydrolysis. Minutissamides E–L (1–8) exhibited antiproliferative activity against MDA-MB-435 cells with IC50 values ranging between 1 and 10μM. The structures of minutissamides E–L (1–8) were closely related with those of the previously reported lipopeptides, puwainaphycins A–E and minutissamides A–D, characterized by the presence of a lipophilic β-amino acid and three non-standard amino acids NMeAsn, OMeThr and Dhb (α,β-dehydro-α-aminobutyric acid). The strain UIC 10035 was designated as cf. Anabaena sp. on the basis of morphological and 16S rRNA gene sequence analyses.