Chemical investigation of the marine sponge Dysidea avara, collected from the South China Sea, yielded 13 steroids, including nine new (1–9) and four known (10–13) ones. The new structures were elucidated as (3S,14R)‐3,14‐dihydroxycholesta‐5,8‐dien‐7‐one (1), (22E,24R)‐7α‐ethoxy‐5α,6α‐epoxyergosta‐8(14),22‐dien‐3β‐ol (2), 3β‐hydroxy‐7α‐ethoxy‐5α,6α‐epoxy‐8(14)‐cholestene (3), 3β,5α‐dihydroxy‐6α‐ethoxychofesta‐7,9(11)‐diene (4), 3β,5α‐dihydroxy‐6β‐ethoxycholest‐7‐ene (5), (22E,24R)‐24‐ethoxy‐3β,5α‐dihydroxy‐6β‐ethoxyergosta‐7,22‐diene (6), (22E)‐3β,5α‐dihydroxy‐6β‐ethoxycholesta‐7,22‐diene (7), 24‐ethoxy‐3β,5α‐dihydroxy‐6β‐ethoxycholest‐7‐ene (8 and 9), by extensive spectroscopic analyses, such as HR‐ESI‐MS, 1D and 2D NMR data. The absolute configuration of 1 was assigned by comparison the experimental ECD spectra with the calculated ones. Among the 13 metabolites, compounds 1, 4, 11, 12, and 13 showed NF‐κB inhibitory activities in human HER‐293 cells with IC50 values of 6.4, 18.7, 8.1, 9.6, and 7.5 μM, respectively. Preliminary structure−activity relationship analysis unveiled that the conjugated ketones or unsaturated double bonds might be the functional groups for the five active steroids.
