New beta-caryophyllene-derived terpenoids from the soft coral Sinularia nanolobata

Abstract

Two new norsesquiterpenoids, nanonorcaryophyllenes A (1) and B (2), two new diterpenoids, nanolobatins A (3) and B (4), and a novel norditerpenoid, nanolobatin C (5), were isolated from the n-hexane extract of the Taiwanese soft coral Sinularia nanolobata. Also, two new furanone derivatives, 6 and 7, were isolated for the first time from natural sources. The structures of 1-5 were elucidated on the basis of extensive spectroscopic analyses and by comparison of the spectral data with those of the related metabolites. Nanonorcaryophyllenes A (1) and B (2) were characterized as 13-norcaryophyllenes that lack a methyl group at C-11, while nanolobatin C (5) represents the first example of a xeniaphyllane-based 17-norditerpenoid. The cytotoxicity of 1-6 against the growth of a limited panel of cancer cell lines is also described.