Stress induced carbazole phytoalexins in Glycosmis species

Induced formation of a series of carbazole alkaloids was observed in leaves of Glycosmis parviflora and G. pentaphylla after wounding, UV-irradiation, and particularly after inoculation with the fungus Botrytis cinerea. Chemi cal variation between different provenances and even individuals of G. parv iflora led to an accumulation of different derivatives from which three pro ved to be undescribed natural products. Their structures were identified by spectroscopic methods and named carbalexins A, B, and C. Bioautographic te sts on TLC plates with Cladosporium herbarum exhibited strong antifungal ac tivity for the new carbalexins as well as for the already known 2-hydroxy-3 -methylcarbazole, but only weak effects for the pyranocarbazole glycoborini ne. Detailed experiments with marked infection areas confirmed the restrict ed accumulation of carbazole derivatives which could not be detected in non -infected areas of the same leaf. Apart from carbazoles. in some individual s of G. parviflora an additional accumulation of the pyranoquinolones flind ersine and methylflindersine was induced, which supports the already previo usly discussed biogenetic connections between carbazoles and prenylated qui nolones, (C) 2001 Elsevier Science Ltd. All rights reserved.