PHYTOTOXIC COMPOUNDS FROM ESENBECKIA YAXHOOB

Investigation of the aerial parts of Esenbeckia yaxhoob Lundell (Rutac eae) led to the isolation of a new dammarane-type of triterpene which was characterized by spectral means as (24S)-24-methyl-dammara-20,25-d iene-3 beta-yl-acetate. In addition, 2-tridecanone, asarinin, imperato rin, lupeol and hesperidin were obtained. (24S)-24-Methyl-dammara-20,2 5-diene-3 beta-yl-acetate, 2-tridecanone, asarinin and imperatorin cau sed significant inhibition of the radicle growth and/or germination of seedlings of Amaranthus hypochondriacus, Echinochloa crusgalli, Lactu ca sativa and Lycopersicum esculentum. Also, it has been found that im peratorin inhibited ATP synthesis and both phosphorylating and uncoupl ed electron flow from H2O to K-3[Fe(CN)(6)]. On the other hand, this c oumarin stimulated the basal electron flow from H2O to K-3[Fe(CN)(6)] and the activity of the light-activated Mg2+-ATPase. These effects wer e measured in freshly lysed illuminated spinach chloroplasts and allow ed to determine that imperatorin acts as an uncoupler and as a Hal rea ction inhibitor. (C) 1998 Elsevier Science Ltd. All rights reserved.