Uncommon 4-methylpregnane and anti-inflammatory 5α,8α-epidioxysterols from the South China Sea soft coral Sarcophyton sp.

One uncommon 4-methylpregnane-type steroid (1), four previously undescribed 5α,8α-epidioxysterols (3–6), along with two known compounds (2 and 7), were isolated from the Chinese soft coral Sarcophyton sp. A distinguishing feature of 3–6 was the presence of a rare 1,2-dioxane ring system, which has not been frequently reported in the steroids from Sarcophyton genus. Their structures were determined by extensive spectroscopic analysis, comparison with the spectral data reported in the literature and X-ray diffraction analysis. In in vitro bioassays, compounds 3–6 exhibited significant anti-inflammatory activities, with the peroxide bridge in the B-ring hypothesized to play a key role in these effects. The results underscore the therapeutic potential of marine-derived steroidal compounds, particularly for the treatment of inflammatory diseases. This study highlights the South China Sea soft corals as a valuable resource for bioactive compounds and offers new directions for drug discovery in the field of anti-inflammatory therapies.