Unusual steroids from the sponge-associated fungus Aspergillus pulvericola

Two new steroids, 23-methyl rubensteroid A (1) and (22E,24R)-23-methylergosta-7,9(11),22-triene-3β,5α,6α-triol (3), were obtained from the sponge-associated fungus Aspergillus pulvericola along with eight known analogues (2, 4–10). The structures of the new compounds were elucidated by a combination of spectroscopic analysis and comparison with previously reported data. Both new compounds contain a 23-methylergosterol side chain. Compound 1 represents an unprecedented sterol scaffold with 32 carbon atoms that is characterised by an unusual aromatic ring embedded within the core structure. The bioactivities of these compounds were evaluated by assessing their inhibitory activities against LPS-induced NO production in both RAW264.7 and BV2 cells. (22E,24R)-Ergosta-7,9(11),22-triene-3β,5α,6α-triol (4) and (22E,24R)-23-methylergosta-7,22-dien-3β,5α,9α-triol-6-one (6) demonstrated significant inhibitory activity at a concentration of 10 μM. This work represents the first report on the secondary metabolites produced by the fungus A. pulvericola, giving insight into the chemical and biological potential of the fungus.