Manadosterols A and B, Sulfonated Sterol Dimers Inhibiting the Ubc13-Uev1A Interaction, Isolated from the Marine Sponge Lissodendryx fibrosa

Two new dimeric sterols, manadosterols A (1) and B (2), were isolated from the marine sponge Lissodendryx fibrosa collected in Indonesia. The two compounds are comprised of two sulfonated sterol cores connected through the respective side chains. Manadosterols A (1) and B (2) inhibited the Ubc13-Uev1A interaction with IC50 values of 0.09 and 0.13 mu M, respectively. They are the second and third natural compounds showing inhibitory activities against the Ubc13-Uev1A interaction and are more potent than leucettamol A (IC50, 106 mu M), the first such inhibitor, isolated from another marine sponge.