Surfactin isoforms isolated from a mushroom derived Bacillus halotolerans DMG-7-2

A new iso-C₁₄ [Val², Val⁷] surfactin isoform (1) together with eight known ones (2–9), was isolated from the culture of a mushroom derived bacterium, Bacillus halotolerans DMG-7-2. The structures of them were mainly elucidated by NMR and MS data, and the NMR data of 5 also was reported for the first time. The absolute configuration of 1 was determined by Marfey’s analysis (for amino acid residues) and the ¹³C NMR calculation of the two plausible epimers of 1 (for fatty acid). Compounds 1–9 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 µM, and the IC₅₀ values of the positive control 5-FU were 99.94, 71.49 and 0.12 µM, respectively.