Microbiological transformation of the aryltetralone lignan (−)-8′-epi-aristoligone (1) with Cunninghamella echinulata ATCC 10028B afforded two known natural lignans, (−)-holostyligone (3) and (−)-arisantetralone (4). Incubation of the aryltetralin lignan (−)-isogalbulin (2), obtained by chemical transformation of 1, with C. echinulata ATCC 10028B afforded the known lignan aryltetralol (5) and seven new metabolites, (−)-8-hydroxyisogalbulin (6), (−)-7-methoxyisogalbulin (7), (−)-4′-O-demethyl-8-hydroxyisogalbulin (8), (−)-7-methoxy-8-hydroxyisogalbulin (9), (−)-4′-O-demethyl-7-methoxyisogalbulin (10), (−)-4′,5-O-didemethylcyclogalgravin (11), and (−)-4′-O-demethylcyclogalgravin (12). When 2 was subjected to biotransformation with Beauveria bassiana ATCC 7159, (−)-8-hydroxyisogalbulin (6) was the only isolable product. The structures of all new compounds were established by detailed analysis of their spectroscopic data.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade Estadual Paulista Júlio de Mesquita Filho, Instituto de Química de Araraquara, Araraquara, Av. Prof. Francisco Degni, 55, Quitandinha, CEP 14801-970, SP, BrasilUniversidade Estadual Paulista Júlio de Mesquita Filho, Instituto de Química de Araraquara, Araraquara, Av. Prof. Francisco Degni, 55, Quitandinha, CEP 14801-970, SP, Brasil