XiapyrrolesA–F: <i>N</i>‑AlkylpyrroleAlkaloids from the Marine-Derived Actinomycete <i>Streptomycesxiamenensis</i> 1310KO-148

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