Dysifragilones A–C, Unusual Sesquiterpene Aminoquinones and Inhibitors of NO Production from the South China Sea Sponge Dysidea fragilis

Dysifragilones A–C (1–3), three unusual sesquiterpene aminoquinones based on a rearranged avarone skeleton, were isolated from the South China Sea sponge Dysidea fragilis. Their structures were elucidated by detailed spectroscopic and spectrometric analysis, and their absolute configurations were assigned from calculated electronic circular dichroism (ECD) spectra. The inhibitory activity of each compound on the production of nitric oxide (NO) stimulated by lipopolysaccharide (LPS) in mouse RAW 264.7 macrophages was evaluated. Of the three metabolites, dysifragilone A (1) showed the most potent inhibitory activity, with an IC50 value of 6.61 ± 0.54 μM.