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 Mosher's 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.

Graphical abstractDownload full-size imageNew eunicellin-based diterpenoids, were isolated from the soft coral, Cladiella hirsuta.