Blasticidin A (
1), an antibiotic, has strong inhibitory activity toward aflatoxin production by
Aspergillus parasiticus. We prepared some derivatives of
1 and examined their biological activities. Among them, derivatives
3 and
4 without the tetramic acid moiety of
1 maintained inhibitory activity toward aflatoxin production, but did not show antifungal activity or toxicity. RT-PCR experiments indicated that derivatives
3 and
4 as well as
1 significantly reduced the expression of genes encoding aflatoxin biosynthetic enzymes (
pksA,
ver-1 and
omtA) and a regulatory gene (
aflR) in
A. parasiticus. These results suggested that derivatives
3 and
4 can inhibit aflatoxin production more specifically than
1 by inhibiting an early step prior to the expression of
aflR in the pathway of aflatoxin biosynthesis.
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