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FEMS Microbiol Lett. 2008 Jul;284(2):184-90. doi: 10.1111/j.1574-6968.2008.01195.x. Epub 2008 May 19.

Spiroethers of German chamomile inhibit production of aflatoxin G and trichothecene mycotoxin by inhibiting cytochrome P450 monooxygenases involved in their biosynthesis.

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Department of Applied Biological Chemistry, The University of Tokyo, Tokyo, Japan.


The essential oil of German chamomile showed specific inhibition toward aflatoxin G(1) (AFG(1)) production, and (E)- and (Z)-spiroethers were isolated as the active compounds from the oil. The (E)- and (Z)-spiroethers inhibited AFG(1) production of Aspergillus parasiticus with inhibitory concentration 50% (IC(50)) values of 2.8 and 20.8 microM, respectively, without inhibiting fungal growth. Results of an O-methylsterigmatocystin (OMST) conversion study indicated that the spiroethers specifically inhibited the OMST to AFG(1) pathway. A cytochrome P450 monooxygenase, CYPA, is known as an essential enzyme for this pathway. Because CYPA has homology with TRI4, a key enzyme catalyzing early steps in the biosynthesis of trichothecenes, the inhibitory actions of the two spiroethers against TRI4 reactions and 3-acetyldeoxynivalenol (3-ADON) production were tested. (E)- and (Z)-spiroethers inhibited the enzymatic activity of TRI4 dose-dependently and interfered with 3-ADON production by Fusarium graminearum, with IC(50) values of 27.1 and 103 microM, respectively. Our results suggest that the spiroethers inhibited AFG(1) and 3-ADON production by inhibiting CYPA and TRI4, respectively.

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