Lemnalosides A-D, decalin-type bicyclic diterpene glycosides from the marine soft coral Lemnalia sp.

Four new decalin-type bicyclic diterpenoids, lemnalosides A-D (1-4), along with one known decalin-type bicyclic diterpenoid, lemnabourside (5), were isolated from an extract of the marine soft coral Lemnalia sp. The structures of the new compounds were elucidated on the basis of spectroscopic analysis including 1H-1H COSY, HMQC, HMBC, NOESY, HRESIMS, UV, IR, and chemical means. Compound 1 showed moderate activity in the hyphae formation inhibition (HFI) assay against Streptomyces 85E at a concentration of 20 microg/disk, while compound 2 displayed inhibitory activity in the HFI assay at a concentration of 2.5 microg/disk.