New Steroids from the South China Sea Soft Coral Lobophytum sp.

Two new steroids, (22R,23S)-3β-hydroxy-23-methyl-17,20-epoxyergost-5-en-22-yl acetate and (22R,23S)-5-hydroperoxy-23-methyl-5α-17,20-epoxyergost-6-ene-3β,22-diol, were isolated from the South China Sea soft coral Lobophytum sp., together with two related known ones. The structures of all compounds were elucidated by extensive spectroscopic analysis and by comparing their spectral data with those previously reported. The structure of (22R,23S)-3β-hydroxy-23-methyl-17,20-epoxyergost-5-en-22-yl acetate was further confirmed through chemical correlation. All the isolates were evaluated for the in vitro inhibitory activity against NF-κB, a potential target for the treatment of cancer, and (22R,23S)-5-hydroperoxy-23-methyl-5α-17,20-epoxyergost-6-ene-3β,22-diol exhibited moderate inhibition activity with IC50 value of 8.96 μg/mL.