In order to find new natural products with anti-inflammatory activity, chemical investigation of a 3000-meter deep-sea sediment derived bacteria Bacillus subtilis B5 was carried out. A new macrolactin derivative was isolated and identified as 7,13-epoxyl-macrolactin A (1). Owing to the existence of the epoxy ring, 1 exhibited a significant inhibitory effect on the expression of inducible nitric oxide and cytokines, compared with previously isolated known macrolactins (2–5). Real-time Polymerase Chain Reaction (PCR) analysis showed that the new compound significantly inhibited the mRNA expressions of inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Reverse transcription-PCR analysis demonstrated that the new compound reduced the mRNA expression level of IL-1β in a concentration-dependent manner.

This work investigated the metabolites and their biosynthetic functional hydroxylase genes of the deep-sea sediment metagenomic clone 25D7. 5-Bromoindole was added to the 25D7 clone derived Escherichia coli fermentation broth. The new-generated metabolites and their biosynthetic byproducts were located through LC-MS, in which the isotope peaks of brominated products emerged. Two new brominated bis-indole metabolites, 5-bromometagenediindole B (1), and 5-bromometagenediindole C (2) were separated under the guidance of LC-MS. Their structures were elucidated on the basis of 1D and 2D NMR spectra (COSY, HSQC, and HMBC). The biosynthetic functional genes of the two new compounds were revealed through LC-MS and transposon mutagenesis analysis. 5-Bromometagenediindole B (1) also demonstrated moderately cytotoxic activity against MCF7, B16, CNE2, Bel7402, and HT1080 tumor cell lines in vitro.