Chaetomium mycotoxins with antiinsectan Or
antifungal activity
Authors
Submitted to: Meeting
Abstract
Publication Acceptance Date:
September 10, 1999
Publication Date: N/A
Abstract only
Technical Abstract: The genus Chaetomium was targeted as a
potentially rich source of
antiinsectan natural products
because different Chaetomium species
have been shown to be avoided by or
harmful to fungus- feeding insects.
Chaetomium globosum is recognized
for its biocontrol potential in crop
protection against fungal plant
pathogens. Only recently, however,
has experimental evidence been
offered to show that chetomin is the
chemical basis for this observed
antagonism. Bioassay guided studies
using both antiinsectan assays (Helicoverpa
zea) and antifungal assays
(Aspergillus flavus) led us to a
variety of known Chaetomium
metabolites (i.e., antibiotic 1233A;
chaetochromins; chaetoglobosin A, B,
D, and F; 19-O-acetylchaetoglobosin
A and D; chaetoviridins A, B, and X;
chetocin; chetomin; dethiotetra (methylthio)chetomin;
cochliodinol, cyclosporin A and C;
eugenitin; sterigmatocystin; O-methylsterigmatocystin).
Two novel compounds closely related
to cytochalasins but with previously
undescribed ring systems were
discovered to have antiinsectan
activity. One of these compounds was
chaetochalasin A from Chaetomium
brasiliense NRRL 22999, a culture
isolated from a sclerotium of
Aspergillus flavus that we buried in
a corn field near Tifton, Georgia,
USA. Among the compounds isolated in
this work, only cyclosporin A and
sterigmatocystin had been previously
reported to have toxicity to
insects. Most of these compounds
were originally isolated as
mycotoxins. The study confirmed our
hypothesis that Chaetomium spp.
produce potent insecticides as
chemical defenses.
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