Xiapyrroles A-F: N-Alkylpyrrole Alkaloids from the Marine-Derived Actinomycete Streptomyces xiamenensis 1310KO-148.

Six new N-alkylpyrrole alkaloids (1-6) were isolated from the marine-derived actinomycete Streptomyces xiamenensis 1310KO-148 from a sponge sample. The structures of xiapyrroles A-F (1-6) were elucidated by detailed analysis of extensive spectroscopic data, including 1D, 2D NMR, and HRESIMS data. The absolute configurations of 2, 3, 4, and 6 were determined by a comparison of their calculated and experimental electronic circular dichroism (ECD) spectra. The position of the hydroxamate group in 6 was confirmed through NO-methylation and NOESY data analysis. All compounds (1-6) were tested for their anti-inflammatory effects in LPS-stimulated RAW 264.7 cells, a mouse macrophage cell line. The treatment of RAW 264.7 cells with 30 μM of 1-6 showed no significant cytotoxic effects. However, 1 dose-dependently suppressed the LPS-induced production of NO (IC50 = 29.5 μM) and interleukin-6 (IL-6) (IC50 = 10.9 μM). Compound 1 exhibited no potential cytotoxicity against six solid cancer cell lines and eight blood cancer cell lines at a concentration of 30 μM.