The novel 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) inhibitors known as sterenin A, B, C and D were found in a solid-state culture of the producing basidiomycetes identified as Stereum sp. SANK 21205. Purification of the 50% aq Me(2)CO extract of the culture was performed by EtOAc extraction, reversed phase open-column chromatography and successive ODS HPLC preparation. These compounds, whose structures were determined by several spectroscopic methods, were found to be novel isoindolinone alkaloids which exhibited potent selective inhibitory activities against 11beta-HSD1.