Introduction: The order Sapindales (APG III, 2012) belongs to the clade Rosids, more specifically the Eurosids II group, consisting of 9 families, 471 genera and 6700 species distributed in the tropical flora. It contains about 3% of eudicot diversity and it shows quite high diversification rates. There was some difficulty in classifying the families over the years, and different classification were proposed by Takhtajan (1987), Cronquist (1988), Dahlgren (1989), Thorne (1992) and others. The main problem that Sapindales is one of the largest order in number of genera and species, thus, it is complicated to unify them based on one single characteristic (Gadek, 1996). Then, based on the most modern classification system, APG III, this study aimed at assessing chemosystematic trends in Sapindales by evaluating their chemical micromolecules taxa, in order to select chemical markers.
Methods: The chemical data were collected in the period from January 2010 to February 2014 from various online databases, including PUBMED, Onefile, Scorpus, SciVerse, Science Direct,Web of Science, Sci-finder, MEDLINE, Springerlink, Directory of Open Acess Journals, Biomed Central, SciELO, American Chemical Society, Sage Publications, and Wiley Online Library. The keywords used in the search were the names of compounds, chemistry, chemical composition and the names of the genera belonging to each family of Sapindales. The system of classification used for this study was APG III (2012). Selected micromolecules were classified according to the their occurrence number (ON) (number of compounds of each chemical class produced by a taxon) and percentage of occurrence (ON%) for each class. The chemical parameter ON was established as the sum of the number of times the secondary metabolites structural types were cited per species indicating a degree of importance of a class of metabolites for a chosen taxon. In addition, by counting the same substance several times, it was possible to characterize its production trend for a given taxon (Gottlieb et al., 1996). The parameter ON was used to determine the markers, a class of metabolites that represents the taxon and is used for the identification each family
Results and discussion: The chemistry of Sapindales is very diverse and the families most studied from the chemical point of view are Rutaceae, Anacardiaceae and Burseraceae. No compound isolated from Kirkiaceae has been found in the literature. Among the classes of secondary metabolites found in Sapindales, there are alkaloids, methylxanthines, aromatic polyketides, chromones, coumarins, xanthones, flavaglines, flavonoids, stilbenes, simple phenolics, lignans, lignins, quinones, tannins, terpenes and saponins. The class of metabolites with the highest ON in the order were the terpenes (ON = 3,511), including apocarotenoids, carotenes, diterpenes, limonoids, meroterpenes, monoterpenes, quassinoids, sesquiterpenes, sesterterpenes, sterols, triterpenes, and others. Flavonoids were found in all families except Kirkiaceae, and because of this wide distribution in the order, they could be a good chemical marker for Sapindales. However, evaluating the isolated families, we can see some peculiarities: Anacardiaceae is rich in aromatic polyketids such as anacardic acids, Biebersteiniaceae predominantly were isolated flavonoids, Burseraceae is the largest producer of terpenes among families, Meliaceae produces a specific class of metabolites named flavaglines, Nitrariaceae and Simaroubaceae are major producers of alkaloids and Sapindaceae of saponins. Given this great diversity of secondary metabolites produced in the order Sapindales it is essential to deepen the studies in the sense of linking other parameters that aid in the classification of these families.
References: Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 12, July 2012; Gadek, P. A. [et al. 1996], Fernando, E. S., Quinn, C. J., Hoot, S. B., Terrazas, T., Sheahan, M. C., Chase, M. W. 1996. Sapindales: Molecular delimitation and infraordinal groups. American J. Bot. 83: 802-811; Gottlieb, O.R., Kaplan, M.A.C., Borin, M.R.M.B., 1996. Biodiversidade: um enfoque químico-biológico. Editora da UFRJ, Rio de Janeiro.