PROFILE OF QUINOLIZIDINE ALKALOIDS IN ULE X SPECIES P. Máximo and A. Lourenço

1. PROFILE OF QUINOLIZIDINE ALKALOIDS INULEX SPECIES P. Máximo and A. Lourenço Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa, Quinta da Torre, 2825-114 Caparica, Portugal. INTRODUCTION The Ulex genus (Leguminosae, subfamily Papilionoideae) grows in Portugal as different species, through large extensions of the country. Some of these species are spread in restrict areas and have distinct morphological characters while others, that grow on the central zone of the country, whose characterisation is ambiguous and that have been classified differently by several authors under the designation of U. parviflorus. More recently a new work has appeared [1] that, after the analysis of a large number of specimens, makes the distinction between the taxa on the basis of morphological, chromosomic, ecological and geographic factors. Considering this latter botanical classification and with the intention to add chemical information to it, here we present the quinolizidine alkaloids (QA) profiles of the 19 Ulex taxa and the chemotaxonomic considerations deduced from them. Ulex australis Clemente subs. Welwitschianus (Planchon) Espírito Santo, Cubas, Lousã Ulex densus Webb Ulex species Ulex jussiaiei Webb 1.1/94 2.1/94 3.1/94 2/95 4/95 4/96 5/96 1/98 1/95 3/95 1/96 2/96 3/96 1/97 2/97 Taxa designation Ulex airensis Espírito Santo, Cubas, Lousã Ulex minor Roth. Ulex europaeus L. 2/98 5/98 1.2/94 1.3/94 RESULTS AND DISCUSSION In 19 taxa from 6 different species of Portuguese Ulex (Table 1), a dipiperidine alkaloid (ammodendrine), 16 known quinolizidine alkaloids (sparteine, b-isosparteine, N-methylcytisine, cytisine, hydroxysparteine, 5,6-dehydrolupanine, rhombifoline, lupanine, hydroxy-N-methylcytisine, N-formylcytisine, N-acetylcytisine, anagyrine, pohakuline, dehydrobaptifoline, baptifoline and epibaptifoline) and 4 new quinolizidine alkaloids (jussieiines A-D) [2] were identified by GC and GC-MS analysis. These alkaloids were detected in almost each species and are, apparently, a typical QA profile of Portuguese Ulex. The different characteristics between species seems to be the relative amount of the 7 more abundant alkaloids present (cytisine, N-methylcytisine, anagyrine and jussiaeiines A-D). The quantitative GC analysis of these QA was performed for all taxa and by principal component analysis (PCA) the amount of each alkaloid in each taxa provided the grouping of the several species (Graph 1). Ulex europaeus and Ulex minor are isolated from the other species and form Group 1. Graph 1 Factor analysis by principal component extractionof 19 taxa of Portuguese Ulex. PCA was performed for the remaining species (Graph 2) providing the identification of 3 more major groups: Group 2 (2/97, 4/95, 4/96 and 5/96), Group 3 (3/95 and 2/96)and Group 4 (1/95, 1/96, 3/96, 1/97, 1/98, 2/98and 5/98). Species 1.1/94, 2.1/94, 3.1/94 and 2/95 are in-between taxa. From this study the well characterised species U. airensis, U. australis,U. densus, U. europaeus, and U. minor form individual groups with characteristic quinolizidine alkaloid profiles. Some of the taxa known as U. jussiaei are still undefined and others are distribute over the former groups. Confronting both statistical and botanical classification we can make the following comments: U. europaeus and U. minor, U. australis and U. airensis can be considered as different species, representing Groups 1, 2 and 4, respectively. The taxa classified as U. densus can be separated in two chemodemes, D1 and D2; one we can consider as the ‘true densus’ represented by chemodeme D1 (we now rename Group 3), clearly isolated from the remaining Groups, and chemodeme D2 we include in Group 4. Interestingly, the previous species classified as U. jussiaiei, the most controversial botanical species, is wide spread. Some of it’s taxa are included in Groups 2 and 4 (4/95, 4/96 and 5/96, 1/98, respectively) and some (1.1/94, 2.1/94, 3.1/94 and 2/95) are still undefined. From biosynthetic considerations probably these later taxa are in an intermediate stage of development towards any of the other species or represent hybrid forms. Graph 2 Factor analysis by principal component extractionof 17 taxa of Portuguese Ulex. In order to establish the resemblance between species, specimens classified on the basis of morphological characters as U. europaeus (1.3/94), U. minor (1.2/94), U. densus (3/95, 2/96), U. australis (2/97) and Ulex airensis (2/98, 5/98) were submitted to cluster analysis. The results obtained are depicted in Graph 3. Analysis of this graph confirms the results previously obtained by principal component analysis and once more, U. europaeus and U. minor, are clearly isolated from the remaining species. Closest to these we find U. densus that reveals close proximity to U. australis and U. airensis. CONCLUSIONS Portuguese Ulex is rich in a-pyridone type QA. The most abundant alkaloids in each specimen are cytisine, N-methylcytisine, anagyrine and jussiaeiines A-D. Statistic treatment of the amount of each of these alkaloids allowed us to classify the several taxa in 5 different species which are in good agreement with botanical classification. Jussiaeiines A-D apparently play a relevant role in differentiating Portuguese U. and the occurrence of these alkaloids in each species may be related to the phylogeny of the genus. Graph 3 Cluster analysis based on chemical characters of U. europaeus (1.3/94),U. minor (1.2/94), U. densus (3/95, 2/96), U. australis (2/97)and Ulex airensis (2/98, 5/98). ACKNOWLEDGMENTS We wish to thank the staff of the Herbário, Museu,Jardim Botânico, Faculdade de Ciências, Universidade de Lisboa, Portugal, for collecting and classifying the plant material. We wish to thank Prof. Michael Wink and Andreas Tei, from the Institut für Pharmazeutische Biologie, Universitat Heidelberg, Germany, for the mass spectra. One of us (P. M.) wishes to thank FCT (Portugal) for a PRAXIS XXI fellowship. REFERENCES [1] Espírito-Santo, M. D., Cubas, P., Lousã, M. F., Pardo, C. and Costa, J. C. (1997) Anal. Jar. Bot. de Madrid55, 49. [2] Máximo, P. and Lourenço, A. (2000) J. Nat. Prod. 63 (2), 201.