Sesterterpene sulfates as isocitrate lyase inhibitors from tropical sponge Hippospongia sp.

Two sesterterpene sulfates (1–2) were isolated from tropical sponge Hippospongia sp. and their inhibitory activities against isocitrate lyase (ICL) from the rice blast fungus Mgnaporthe grisea were evaluated. Compound 3 was obtained by hydrolysis of compound 1. Compounds 1 and 3 were found to be potent ICL inhibitors, which inhibited appressorium formation and C2 carbon utilization in M. grisea. Our results suggest that ICL plays crucial role in appressorium formation of M. grisea and is a new target for the protection of rice blast disease.