PROFILE OF QUINOLIZIDINE ALKALOIDS IN ULEX 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
Ulex jussiaiei
Ulex densus
Webb
Webb
Taxa
designation
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
species
Ulex australis
Clemente subs. Welwitschianus
(Planchon) Espírito Santo, Cubas, Lousã
2/97
Ulex airensis
Espírito Santo,
Cubas, Lousã
2/98
5/98
Ulex minor
Roth.
Ulex europaeus
L.
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, Nmethylcytisine, 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.
H3CO
N
H3CO
NCH3
CH2OH
CH2OH
jussiaeiine A
jussiaeiine B
R1 = R2 = H
jussiaeiine C
R1 = OH; R2 = H
jussiaeiine D
R1 = H; R2 = OH
N
O
1.3/94
1.2/94
N
NH
O
N
O
Graph 1
Factor analysis by principal component extraction of 19 taxa of
Portuguese Ulex.
5 /9 8
2 /9 8
3 /9 6
1 /9 7
1 /9 6
2 . 1 /9 4
2 /9 7
1 /9 5
5 /9 6
4 /9 5
4 /9 6
2 /9 5
3 . 1 /9 4
1 . 1 /9 4
3 /9 5
2 /9 6
Graph 2
Factor analysis by principal component extraction of 17 taxa of
Portuguese Ulex.
Com plete Linkage
Squared Euclidean distances
1.2/94
1.3/94
3/95
2/96
2/97
2/98
5/98
2000
4000
6000
8000
10000
N
(-)-N-methylcytisine
1 /9 8
0
N
R1
NCH3
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.
N
R2
12000
14000
16000
Linkage Distance
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).
H
(-)-anagyrine
(-)-cytisine
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, 2/98
and 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.
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.
REFERENCES
[1] Espírito-Santo, M. D., Cubas, P., Lousã, M. F., Pardo, C. and Costa, J. C. (1997) Anal. Jar. Bot. de
Madrid 55, 49.
[2] Máximo, P. and Lourenço, A. (2000) J. Nat. Prod. 63 (2), 201.
CONCLUSIONS
Portuguese Ulex is rich in a-pyridone type QA. The most
abundant alkaloids in each specimen are cytisine, Nmethylcytisine, 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.
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.