Phytotoxic compounds from Esenbeckia yaxhoob

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