01856naa a2200265 a 450000100080000000500110000800800410001910000200006024501030008026000090018352011250019265000200131765000160133765000190135365000240137265000160139665000170141265000200142965000120144970000200146170000170148170000160149870000160151477300600153019394342012-11-12       2012    bl uuuu     u00u1 u    #d1 aCERDEIRA, A. L.  aTabanone, a new phytotoxic constituent of cogongrass (Imperata cylindrica).h[electronic resource]  c2012  aCogongrass is a troublesome, invasive weedy species with reported allelopathic properties. The phytotoxicity of different constituents isolated from roots and aerial parts of this species was evaluated on garden lettuce and creeping bentgrass. No significant phytotoxic activity was detected in the methylene chloride, methanol, or water extracts when tested at 1.0 mg ml21. However, the total essential oil extract of cogongrass aerial parts was active. Bioactivity-guided fractionation of this extract using silica gel column chromatography led to the identification of megastigmatrienone, 4-(2-butenylidene)- 3,5,5- trimethyl-2-cyclohexen-1-one (also called tabanone), as a mixture of four stereoisomers responsible for most of the activity. Tabanone inhibited growth of frond area of lesser duckweed, root growth of garden onion, and fresh weight gain of garden lettuce with 50% inhibition values of 0.094, 3.6, and 6.5 mM, respectively. The target site of tabanone is not known, but its mode of action results in rapid loss of membrane integrity and subsequent reduction in the rate of photosynthetic electron flow.  aAllelochemicals  aAllelopathy  aEssential oils  aImperata cylindrica  aPhytotoxins  aErva daninha  aÓleo essencial  aToxidez1 aCANTRELL, C. L.1 aDAYAN, F. E.1 aBYRD, J. D.1 aDUKE, S. O.  tWeed Science, Champaigngv. 60, n. 2, p. 212-218, 2012.