Dysiscalarones A-E, scalarane sesterterpenoids with nitric oxide production inhibitory activity from marine sponge Dysidea granulosa

Dysiscalarones A-E (1–5), five new scalarane-type bishomoscalarane sesterterpenoids, were isolated from marine sponge Dysidea granulosa collected from the South China Sea, together with two known ones, honulactone A (6) and phyllofolactone I (7). The new structures were determined by extensive spectroscopic analysis including HR-ESI-MS and 1D and 2D NMR data, and their absolute configurations were assigned by single crystal X-ray diffraction analyses. The inhibitory activity of all the seven isolates on the production of nitric oxide (NO) stimulated by lipopolysaccharide (LPS) in mouse RAW 264.7 macrophages was evaluated. Of these metabolites, dysiscalarones A-B (1–2), honulactone A (6), and phyllofolactone I (7) showed inhibitory activities with respective IC₅₀ values of 16.4, 18.5, 2.6, and 3.7 μM, which suggested that the γ-methylated α,β-unsaturated γ-lactone might be the functional group. In addition, all the seven metabolites showed no significant cytotoxicity against lung cancer PC9 cell line at the concentration of 20 μM.