Analysis of metabolites from plants of the Swartzia genus using chemical indexes: evolutionary tendencies

Análise dos metabólitos de plantas do gênero Swartzia usando índices químicos: tendências evolutivas

Analysis of metabolites from plants of the Swartzia genus using chemical indexes: evolutionary tendencies

Análise dos metabólitos de plantas do gênero Swartzia usando índices químicos: tendências evolutivas

A. F. MagalhãesI, ^*; A. M. G. A. Tozzi^II; C. C. Santos^I; E. G. Magalhães^I

^IDepartamento de Química Orgânica, Instituto de Química, UNICAMP, CP 6154, 13084-862 Campinas, SP, Brazil

^IIDepartamento de Botânica, Instituto de Biologia, UNICAMP, CP 6109, 13083-970 Campinas, SP, Brazil

ABSTRACT

The chemical indexes, suggested by Gottlieb et al., have not been used before regarding evolutionary tendency of species in the Swartzia genus. However, the importance of this work encouraged for an analysis of the Swartzia genus using the metabolites isolated from nine species. The analysis, based on calculated chemical indexes, provided an evolutionary tendency for these plants, which correlates with the classification based on morphological analysis.

Keywords: Swartzia; Leguminosae; plant evolution; chemical index; chemotaxonomy.

RESUMO

Os índices químicos sugeridos por Gottlieb et al. não têm sido empregados com respeito à tendência evolutiva das espécies no gênero Swartzia. A importância desse trabalho, entretanto, motivou uma análise usando os metabólitos isolados de nove espécies. A análise baseada nos índices químicos forneceu uma tendência evolutiva para estas plantas que se relaciona com a classificação baseada na análise morfológica.

Palavras-chave:Swartzia; Leguminosae; evolução de plantas; índices químicos; quimiotaxonomia.

Introduction

According to Gottlieb, among other authors, the profile of secondary metabolites in plants can be of taxonomic significance. Thus, chemotaxonomy correlates the profile of secondary metabolites in plants with the botanical classification based on the vegetal morphology. Gottlieb et al. developed a methodology to evaluate the evolutionary tendency of plants based on the biosynthetic route followed by their secondary metabolites as well as the degree of oxidation of these metabolites in each route [1].

The genus Swartzia Schreb. belongs to tribe Swartzieae, subfamily Papilionoideae (Faboideae) of the Leguminosae (Fabaceae), and consists of about 140 species distributed in tropical America [2]. However, only nine species of Swartzia genus have been studied from the phytochemical point of view: S. arborescens, S. laevicarpa, S. langsdorffii, S. leiocalycina, S. madagascariensis, S. polyphylla, S. simplex, S. schomburkii and S. ulei. Most of these studies are about the heartwood flavonoids. The leaves, fruits and seeds of three species were studied looking for saponins. In only two species, S. arborescens and S. langsdorffii were the roots chemically studied, producing abieta-8,11,13-triene diterpenoids [3].

The genus Swartzia was revised by Cowan [4], who recognized two sections, Swartzia sect. Possira (Aubl.) DC. and Swartzia sect. Swartzia. The species S. arborescens is in the section Possira, and the species S. laevicarpa, S. langsdorffii, S. polyphylla, and S. ulei are classified in the section Swartzia, which is divided into two subsection and seven series. S. polyphylla belongs to the subsection Terminales Cowan, which is more primitive. S. leiocalycina and S. langsdorffii are in the series Recurvae Cowan, the species S. laevicarpa and S. ulei are located in the series Benthamianae Cowan, that is more recent, ^{Fluxogram 1}. The species S. madagascariensis was reclassified and renamed as Bobgunnia madagascariensis [5].

In this paper the metabolites furnished by S. langsdorffii Raddi (Synonymous: Mimosa pulchra Vell., Swartzia brasiliensis Vogel and Tounatea langsdorfii (Raddi) Kuntze), a native Brazilian tree [2], included in Swartzia ser. Recurvae of the section Swartzia, were compared with those of other Swartzia species reported in the literature in order to establish infrageneric chemotaxonomic correlations.

Experimental details

Comparing the secondary profile reported for Swartzia species it is possible to observe one group characterized by the presence of flavonoids and another one by the presence of abieta-8,11,13-triene diterpenoids. So, the presence of these classes of metabolites could be used, in addition to morphological data, to define the chemical profile in Swartzia sections: Swartzia sect. Possira characterized by abieta-8,11,13-triene diterpenoids while Swartzia sect. Swartzia by flavonoids. The triterpenoidal saponins could not be used as markers since they appear in both sections.

The flavonoids furnished by the species of Swartzia sect. Swartzia showed a great diversity, which was adequate to evaluate the evolution of these plants according to chemical indexes [6] based on the degree of mean oxidation versus methylation of the flavonoid skeleton (Table 1). The structure showed in Figure 1 was considered as the biosynthetic precursor to calculate the indexes. A higher oxidation versus methylation degree correlates with a higher degree of the plant evolution. S. langsdorffii was excluded because this plant produces abieta-8,11,13-triene diterpenoids [3] and do not produces flavonoids.

In the Swartzia sect. Possira only one species was considered, S. arborescens [7], and its metabolites were compared to the metabolites isolated from S. langsdorffii, using the same proposed parameters [1], because they were very similar.

Results and Discussion

Section and subsection Swartzia:

Figure 2 shows the graph obtained for the correlation of the mean value of oxidation degree versus methylation degree of the flavonoids, calculated for each Swartzia species. Figure 3 shows the same correlation, excluding the species S. madagascariensis, which has been reclassified as Bobgunnia madagascariensis. A much better correlation is obtained.

The basal position of subsection Terminales was confirmed by the calculated indexes and by the position on the graphs.

Section Possira

In the section Possira the comparation of S. arborescens with S. langsdorffii led to three important evolutionary tendencies. The first is that the presence of abietane diterpenoids, and the absence of flavonoids in these species indicate that these species have substituted the shikimate biosynthetic route by the acetate biosynthetic route, which means that these two species are, in the evolutionary sense, more recent than the species belonging to subsection Swartzia.

The second is that, based on S. langsdorffii morphology such as pattern venation, slender, auxiliary and shorter leaf raceme, calyx shape and androecium's characteristics, together with the presence of very similar abietane diterpenoids and the absence of flavonoids, S. langsdorffii is more related to the species of Swartzia sect. Possira, specifically to S. arborescens, suggesting the transfer of S. langsdorffii from section Swartzia to section Possira. The third is that S. arborescens is more recent than S. langsdorffii since its metabolites are more highly oxidized than the metabolites of S. langsdorffii.

Conclusions

The application of chemical indexes according to the methodology proposed by Gottlieb et al. [1, 6] confirmed that (1) S. madagascariensis (renamed Bobgunnia madagascariensis) should not be included in the Swartzia genus, and proposed that (2) Swartzia langsdorffii should be transfer to section Possira.

Acknowledgments

The authors are grateful to the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil, for financial support and to CAPES, Brazil for a scholarship awarded to C. C. Santos, as well as to Dr Carol Collins for critical reading and English revision.

Recebido em: 06/02/2006

Aceito em: 24/03/2006

• [1] O. R. Gottlieb, M. A. Kaplan, M.R. de M. B. Borin,. Biodiversidade: Um Enfoque Químico-Biológico. Editora UFRJ, Rio de Janeiro, 1996, chap. 5.
• [2] V. F. Mansano, and A. M. G. A Tozzi, Brittonia 51 (2) (1999) 149.
• [3] A.F. Magalhães, A.M.G.A. Tozzi, C.C. Santos, E.G. Magalhães, J. Nat. Prod., 68 (8) (2005) 1290.
• [4] R. S. Cowan 1967. Swartzia (Leguminosae, Caesalpinioideae, Swartzieae). Fl. Neotrop. Monogr. 1: 108.
• [5] J. H. Kirkbride, J. H. Wiersema, Brittonia, 49 (1) (1997) 1.
• [6] O. R. Gottlieb, Micromolecular Evolution, Systematics and Ecology- An Essay into a Novel Botanical Discipline, Springer Verlag, Berlin, 1982, 125.
• [7] B. Orphelin, M. Brum-Bousquet, F. Tillequim, M. Koch, C. Moretti, Heterocycles 43 (1) (1996) 173.

Publication Dates

• Publication in this collection
  23 Aug 2006
• Date of issue
  2006

History

• Accepted
  24 Mar 2006
• Received
  06 Feb 2006