Surfactin isoforms isolated from a mushroom derived <i>Bacillus halotolerans</i> DMG-7-2

<p>A new iso-C₁₄ [Val², Val⁷] surfactin isoform (<b>1</b>) together with eight known ones (<b>2</b>–<b>9</b>), was isolated from the culture of a mushroom derived bacterium, <i>Bacillus halotolerans</i> DMG-7-2. The structures of them were mainly elucidated by NMR and MS data, and the NMR data of <b>5</b> also was reported for the first time. The absolute configuration of <b>1</b> was determined by Marfey’s analysis (for amino acid residues) and the ¹³C NMR calculation of the two plausible epimers of <b>1</b> (for fatty acid). Compounds <b>1</b>–<b>9</b> showed moderate cytotoxicity against two human cancer cell lines (A549, MCF-7) and mice microglial BV2 cells, the IC₅₀ values ranged from 8.91 to 33.00 <i>µ</i>M, and the IC₅₀ values of the positive control 5-FU were 99.94, 71.49 and 0.12 <i>µ</i>M, respectively.</p>