Abstract
During investigations on the influence of CaBr2 on the secondary metabolism of Lachnum papyraceum, the production of mycorrhizins and lachnumon type antibiotics was strongly inhibited in bromide-containing culture media. Instead, six isocoumarin derivatives, 6-hydroxymellein (6), 4-chloro-6-hydroxymellein (7), 4-bromo-6-hydroxymellein (9), 6-methoxymellein (10), 4-chloro-6-methoxymellein (11), and 4-chloro-6, 7-dihydroxymellein (12) were isolated. Compounds 7, 9, 11, and 12 have never been isolated from natural sources. 6-Hydroxymellein has been isolated previously from many sources including Gilmaniella humicola and proposed to be a precursor of mycorrhizin A (see reference 6). In comparison to the mycorrhizins, the isocoumarin derivatives exhibited only weak antimicrobial, cytotoxic, phytotoxic, and nematicidal activities.
