5′-O-methyl-14-hydroxyarmillane, a new armillane-type sesquiterpene from cultures of Guyanagaster necrorhiza

Abstract Protoilludene-type sesquiterpene aryl esters are a unique and very diverse compound class that were exclusively isolated from members of the genus Armillaria ( Agaricomycetes , Physalacriaceae ) up to this point. Herein, we describe the isolation and structural characterization of 5′- O -methyl-14-hydroxyarmillane ( 1 ), a new armillane-type derivative, that was obtained from submerged cultures of Guyanagaster necrorhiza (CBS 138623) together with the known congeners melleolide G ( 2 ), melleolide B ( 3 ), and 10-dehydroxy-melleolide B ( 4 ). ROESY data and coupling constants assigned the relative configurations of 1 , while common absolute configurations were confirmed from comparison of its ECD spectrum to the one of 10-hydroxy-5′-methoxy-6′-chloroarmillane ( 5 ). Additionally, the configuration of melleolide G ( 2 ) was revised based on observed ROESY correlations. It is the first time that protoilludene-type sesquiterpene aryl esters were isolated from another genus, namely, Guyanagaster , that is closely related to Armillaria . 1 – 4 were evaluated for their biological activities in a serial dilution assay against several yeast, fungi, and bacteria, as well as in a cytotoxicity assay against different cell lines. Compound 4 was moderately active against Bacillus subtilis , Staphylococcus aureus , and Mucor hiemalis . Furthermore, 1 , 3 , and 4 showed weak cytotoxic effects against the mouse fibroblast cell line L929 and the cervix carcinoma cell line KB3.1.