Four cheilanthane sesterterpenoids, 25-hydroxy-13(24),15,17-cheilanthatrien-19,25-olide (1), 13,16-epoxy-25-hydroxy-17-cheilanthen-19,25-olide (2), 25-hydroxy-13(24),17-cheilanthadien-16,19-olide (3), and 16,25-dihydroxy-13(24),17-cheilanthadien-19,25-olide (4), were isolated from the marine sponge Irciniasp. Compounds 1, 3, and 4 are new natural products. The four compounds inhibit MSK1 (mitogen and stress activated kinase) and MAPKAPK-2 (mitogen activated protein kinase activated protein kinase), two protein kinases involved in mitogen and stress signal transduction.

Bioassay-guided fractionation of the methanol extract of the Australian sponge Neopetrosia exigua led to the isolation of exiguaquinol (2), a new pentacyclic hydroquinone that inhibited Helicobacter pylori glutamate racemase (MurI) with an IC(50) of 4.4 microM. Its structure and relative configuration were assigned on the basis of spectroscopic data. Exiguaquinol (2), bearing a novel pentacyclic ring skeleton, is the first natural product to show inhibition of H. pylori MurI. Its protein-ligand modeling is also discussed.