Biological transformation of the bioactive sesquiterpene, cyclonerodiol (1), isolated from marine-derived fungus Myrothecium sp., was studied. Preparative-scale fermentation of 1 with marine-derived fungus Penicillium sp. resulted in the isolation of a new glycosidic metabolite, 7-O-(beta-D-mannopyranosyl)cyclonerodiol (2). Fermentation of I for 2 weeks with a marine isolate of the actinomycete bacteria Streptomyces sp. also afforded two oxidized geometrical isomers, 10(Z)-and 10(E)-cyclonerotriols (3, 4). The stereostructure of the metabolites obtained was assigned on the basis of detailed spectroscopic data analyses and chemical reaction. (c) 2006 Elsevier Inc. All rights reserved.