Potential allelochemicals from root exudates of invasive Ageratina adenophora

The secondary metabolites from the aerial parts of Ageratina adenophora have been characterized but relatively little is known about the compounds in its root exudates. Three sesquiterpenes, amorpha-4, 7(11)-dien-8- one DTD), eupatorenone, and 9-oxo-ageraphorone) and two esters dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) were purified as phytotoxic compounds from the root exudates of A. adenophora. DBP and DEHP were never identified in this species before. DTD and DBP inhibited the growth of alfalfa more than other compounds. At the highest concentration (500 mg/L), DTD and DBP reduced the shoot height by 42 and 49%, and root length by 31 and 48% than control. Nevertheless, DEHP (9-oxo-ageraphorone) increased the root growth of alfalfa, and their phytotoxic mechanisms on receptor plants were discussed. It is suggested that these compounds played a key role in allelopathy of A. adenophora and this information will advance our knowledge about the potential allelopathic mechanisms of this plant.