ECLÉTICA www.scielo.br/eq química Volume 35, número 3, 2010 Artigo/Article CHEMICAL INDEXES CALCULATED FOR 8,11,13-TRIEN- ABIETANE DITERPENOIDS ISOLATED FROM SWARTZIA SPECIES A. F. Magalhães a*; A. M. G. A. Tozzi b; C. C. Santos a; E. G. Magalhães a. a University of Campinas, UNICAMP, Institute of Chemistry, P. O. Box 6154, 13083-970, Campinas, SP, Brazil b University of Campinas, UNICAMP, Institute of Biology, P. O. Box 6109, 13083-970, Campinas, SP, Brazil aCorrespondence to: Aderbal F. Magalhães. E-mail adress: [email protected] Abstract: The disparity found in the molecular structures of compounds isolated from nine plants of the Swartzia genus indicates that the Swartzia species that furnished cassane diter- penoids and triterpenoidal saponins are more recent, since these metabolites have adopted the mevalonic acid route of formation, abandoning the shikimic acid/acetate route that produces the isoflavonoids found in the remaining species. Chemical indexes calculated from the mole- cular structure diversities of sixteen 8,11,13-trien-abietane diterpenoids isolated from Swartzia langsdorffii and S. arborescens indicate that S. arborescens is more recent than S. langsdorffii. The results suggest a more evolved position in Swartzia species of the section Possira. Keywords: Leguminosae, Systematics of Swartzia genus, plant evolution, chemical index, chemotaxonomy. Introduction common ancestry. Indeed, a systematic study of Swartzia, based on morphological and molecular The genus Swartzia Schreb. belongs to tri- characters, could provide an evolutionary basis to be Swartzieae, subfamily Papilionoideae (Faboi- evaluate the infrageneric taxonomy of Cowan [2]. deae) of the Leguminosae (Fabaceae), and con- Recently, it was pointed out [11] that sists of about 180 species distributed in tropical Swartzia should be retained without further divi- America [1]. It was revised by Cowan [2], who sion, despite its large number of species and con- recognized two sections, Swartzia sect. Possira siderable morphological diversity, because it was (Aubl.) DC. and Swartzia sect. Swartzia, one sub- otherwise resolved as monophyletic, albeit with section, and eight series. limited support. The present resolution of subcla- Nevertheless, studies conducted after this des of Swartzia should be used as a basis for revi- review showed, directly or indirectly, the need of a sing the highly artifi cial infrageneric classifi cation revision of the infrageneric classifi cation, due the of Cowan [2]. artifi ciality of some series [3-10]. In fact, some of Additionally, an updated monograph of the Swartzia species are included in two distinct the entire genus has taxonomic and phylogenetic subsections or series and varieties of the same signifi cance because of the position of Swartzie- species have been placed in different series 11]. ae in the Papilionoideae classifi cation. Molecular Cowan attempted to order the species in his mo- data strongly suggest that Swartzieae sens. strict. nograph along putative phylogenetic lines, but his should be redefi ned to include only the genera infrageneric groups were not intended to refl ect Ecl. Quím., São Paulo, 35 - 3: 169 - 177, 2010 169 Artigo Artigo Article Article Swartzia, Bobgunnia, Bocoa, Candolleodendron, that, instead of isofl avonoids [16-20], furnish ter- Diversity Evaluation- For contextualization and better visualization, the biodiversity observed Trischidium, Cyathostegia, and Ateleia [1,12, 13]. penoids. for ten 8,11,13-trien-abietane diterpenoids isolated from S. langsdorffi , A, B, and 1-4 [21], including a Cladistic analyses showed the group of pair of epimers, 5-8 [22] is explained through a series of methylation and oxidation reactions rationali- Myrospermum, Myroxylon and Myrocarpus of So- zed using a proposed biogenetic route (Fig. 2). phoreae to be associated with the Aldinoid clade Methodology trans-trans-geranylgeranyl pyrophosphate H of the Swartzieae and closely to Swartzieae sens. OH strict. [12]. The reclassifi cation of Swartzieae Disparity Evaluation- The disparity of me- sens. strict., and realignment of the remaining OP tabolites reported in Swartzia genera were evalua- H CH3 swartzioid genera in other tribes, needs to be cor- CH3 ted by comparing their chemical structures since, H roborated by further evidence [1, 13]. methyl group according to Gottlieb’s methodology [14], dispa- H 1,2 migration On the other hand, evolutionary changes in O rity in the molecular structure of special metabo- OH OH plants can also be evaluated through the chemi- D O lites indicates an evolutionary move and occurs Epoxidation [O] cal structures of the special metabolites found in by the replacement of compounds generated from C them, based on the disparity (related to the bioge- CH 3 CH the shikimic acid/acetate biogenetic route by com- A B 3 CH3 netic route) and the diversity of their molecular pounds generated from the acetated route (or me- Cyclization structures [14]. The methodology is very attrac- valonic acid route). tive because it does not imply knowledge of the Accordingly, the species were separated Compound isolated from Myrocarpus frondusus OMe OH complete biogenetic route of metabolites and has [O] into two groups, those that furnished special me- OMe OH HO HO already indicated evolutionary tendencies for the HO OH tabolites originating from the shikimic acid/ace- 1. [Me] Swartzia species that produce isofl avonoids [15]. 1. Epoxidation 2. [O] CO2H tate route - the isofl avonoids, and those that fur- 2. Hydrolysis CO2H In this paper, the methodology is used to suggest nished compounds formed by the mevalonic acid CO2H evolutionary directions for two Swartzia species route - the terpenoids (Table 1). OH OH OMe OH 1. + H2O HO 2. Lactonization HO -H2O HO O Table 1. Correlation between chemical data reported for Swartzia studied phytochemically and botanic clas- O [O] sifi cation (Cowan 1967), phylogeny reported in the current literature (Torke & Schaal 2008). O O O O A swartziarboreol D analogue B [Me] Araujo 2007; Borel et al. OMe OMe Braz Filho et al. Magalhães et al. 1987; Abdel- -H2O OMe Torke & MeO HO Cowan 1967 1980; Osawa et 2005; Orphelin Kader et al. HO Schaal 2008 al. 1992; Dubois et al. 1996 2000; Magalhães O O et al. 1995, 1996 et al. 2003 [Me] O O O O Species Section Series Clade Isofl avonoids Diterpenoids Saponins 4 1 = swartziarboreol C 2 S. ulei Swartzia Benthamianae + [O] [Me] OMe S. laevicarpa Swartzia Benthamianae benthamioid + OMe OMe MeO MeO MeO S. leiocalycina Swartzia Recurvae recurvoid + C D O S. polyphylla Swartzia Orthostyleae orthostyloid + O O A B [O] O S. schomburgkii Swartzia Orthostyleae orthostyloid + O O S. apetala Swartzia Tounateae tournateoid + + 3 7 (A/B = cis) 5 (A/B = cis) 8 (A/B = trans) S. langsdorffi i Swartzia Recurvae acutifolioid + + 6 (A/B = trans) S. arborescens Possira Possira possiroid + Figure 2. Biogenetic proposal rationalized for 8,11,13-trien-abietane diterpenoids isolated and identifi ed S. simplex Possira Possira / Unifoliolatae possiroid + from the native Brazilian tree Swartzia langsdorffi Raddii (Magalhães et al. 2005; Santos et al. 2007). 170 Ecl. Quím., São Paulo, 35 - 3: 169 - 177, 2010 Ecl. Quím., São Paulo, 35 - 3: 169 - 177, 2010 171 Artigo Artigo Article Article The indexes EAO and EAE are found by cal- Σ The initial part of proposed route is very culating the averages: EAO= / N and EAE= similar to that reported for the C-12 methoxy de- Σ / N, where the value N refers to the num- OH rivative of ferruginol [23] including a 1,2-methyl ber of metabolite occurrences, and the O and E 15 si migration. However, the shift now proposed values are the chemical indexes that quantify the HO 12 occurs between C-13 and C-14, and not between oxidative degree of the molecular structures (O) 11 16 C-13 and C-15, and is reinforced by the detection and the carbon skeleton specialization (E) of each 20 of C-14 methylated 8,11,13-trien-abietane com- metabolite. 13 pounds in the species Myrocarpus frondosus [24], The oxidative degree indexes (O) were cal- 1 a species of the Sophoreae tribe, which is closely culated by the equation, O = (x-h)/ n, where the 14 related to Swartzieae sens. strict.. letters n, h and x refer, respectively, to the total O Some cyclization processes are proposed number of carbon atoms (n), the number of C-H 2 9 leading to the compounds that were isolated from bonds (h) and the number of C-heteroatom bon- 10 8 17 Swartzia species and from the species Myrocar- ds (x) of the terpenoid skeleton, while the carbon pus frondosus. The metabolites carbon skeletal skeleton specialization indexes (E) were calcu- 4 5 difference is in ring D, as, in case of the meta- lated by comparing the carbon skeleton of each 3 7 O bolites furnished by M. frondosus , ring D would diterpenoid chemical structure in focus with the be formed by an oxidative cyclization reaction carbon skeleton of a hypothetic common precur- 6 between C-16 and C-12, allowed by the absence sor (compound A; Fig. 1), by using the equation: H of the protective C-12 methoxy group of swart- E = (q + f + c +u) / n, where the letters n, q, f, ziarboreols. In the case of swartziarboreols, ho- c, and u, represent, respectively, the total number 19 18 wever, oxidative steps would occur before a fi nal of carbon atoms (n), the number of C-C bonds cyclization reaction between C-16 and C-17 that broken (q), the number of C-C bonds formed (f), would give rise to the isocoumarin ring D. Then, the number of rings formed with a heteroatom, A = common biogenetic precursor the other compounds would be generated by a se- (c), and the number of additional carbon atoms ries of oxidative and methylation processes. (u). Table 2 shows the O and E values found for Figure 1.