Allelopathic potential of Eupatorium maximiliani Schrad. leaves

Eupatorium maximiliani Schrad leaves were extracted with chloroform:methano l 2:I and the extract was applied to four crops [rice (Oryza saliva L. Cv. Caiapo, corn (Zea mqw L. Cv. AG302A), beans (Phaseolus vulgaris Cv. Carioqu inha) and lettuce (Lachuca saliva Cu. Grand rapids)] and two weed species [ pigweed (Amaranthus spp) and hairy baggarticks (Bidens pilosa L.)]. The ext ract significantly reduced seed germination of lettuce, pigweed and hairy b eggarticks, radicle elongation and shoot growth in lettuce, beans and rice and had no effect on corn. Fractions from Eupatorium extract were obtained through fractionation in silica gel column. Two flavonoids were isolated an d identified through (NMRH)-H-1, (NMRC)-C-13, ME and IR. Bioassays showed t hat 5,6,7,3',4',5'-hexametoxyflavone at 10 mg/l concentration stimulated th e lettuce radicle elongation. The fraction 6 which showed strong biological activity and was found to contain 5,6,7,3 ,4',5'-hexametoxyflavone. This s ubstance has been reported for the first time.