Hirsutalins I–M, eunicellin-based diterpenoids from the soft coral Cladiella hirsuta

New eunicellin-base diterpenoids, hirsutalins I–M (1–5), were isolated from the soft coral Cladiella hirsuta. Their structures were elucidated by spectroscopic methods, particularly in 1D and 2D NMR experiments. The absolute configuration of 2 was determined by Mosherʹs method. These compounds did not exhibit cytotoxicity toward a limited panel of cancer cell lines but showed nitric oxide inhibitory activity in LPS-stimulated RAW264.7 macrophage cells. Among them, compound 3 was found to possess the strongest NO inhibitory activity with an IC50 value of 9.8 μg/mL. Furthermore, 3 was shown to significantly reduce the expression iNOS protein in the same cells.