Perfil metabolômico e avaliação biológica de espécies de Senna e Cassia

Abstract

Species of the genus Senna and Cassia present a wide chemical diversity and relevant biological activity, which motivated us to select two species of Cassia (C. fistula and C. bakeriana) and eight of Senna (S. macranthera, S. occidentalis, S. siamea, S. obtusifolia, S. spectabilis, S. silvestris, S. pendula and S. alata), to be studied from chemical and biological aspects. The ethanol extracts from the leaves and flowers of these species were prepared and analyzed by mass spectrometry (MS) in high resolution with electrospray ionization (ESI). Through chemometric tools of principal component analysis (PCA) and hierarchical cluster analysis (HCA) a study was made in order to group the species that presented a similar metabolic profile. In all analyzes S. spectabilis remains far apart from the others, which can be justified by the presence of the piperidine alkaloids, identified by MS only in this species. The same behavior was observed for S. macranthera, which shown a different metabolic profile, when compared with the other investigated species. The species S. siamea and S. silvestris remain grouped, suggesting that both have a similar composition. MS analysis allowed to identify 48 compounds previously reported in the species, such as flavonoids (aglycones and glycosylated), anthraquinones, chromones, phenolic acids, proanthocyanidins and alkaloids, important for the understanding of PCA and HCA analyzes. The ethanolic extracts of leaves and flowers of all species were submitted to the evaluation of inhibition of pancreatic lipase, antimicrobial and cytotoxic activity. The ethanolic extract of the flowers of C. fistula showed the best result in the inhibition of pancreatic lipase activity with IC50 = 25.68 ± 1.72 µg mL– 1. The best results of the analysis of antimicrobial and cytotoxic activities were observed for the ethanolic extract and ethyl acetate fraction of the S. macranthera flower, which presented antifungal activity against three strains of Candida (C. albicans, C. tropicalis and C. glabrata), with minimum inhibitory concentration (MIC) values ranging from 23.43 to 5.86 μg mL1 which, when compared with the data described in the literature, indicate that the samples are active and promising (MIC ≤ 50 µg mL1) and, the selectivity index (SI) values ranged from 1.34 to 1.94, indicate a low cytotoxicity. Analysis of the S. macranthera flowers ethyl acetate fraction by HPLC-ESI-MS/MS allowed to identify a total of the eighteen compounds, including one organic acid, two flavan-3-ol, one flavone, two glycosylated flavonols, five proanthocyanidin dimers, and seven proanthocyanidin trimers, that are probably associated with the antimicrobial results of this species. Due to the lack of reports in the literature, S. silvestris was selected for a more detailed chemical study aiming at the isolation of secondary metabolites. The ethanolic extract of the flowers was submitted to chromatographic fractionation, which led to the isolation of two anthraquinones, chrysophanol (I) and physcion (II), one fatty acid, palmitic acid (III) four flavonoids, luteolin (IV), aromadendrin (V), luteolin-7-O-glucoside (VIII) and quercetin-3-O-glucoside (IX), a dihydroisocoumarin, 6-dihydroxymellein (VI) and one chormone cassiachromone (VII) which were characterized by spectroscopic (infrared, ultraviolet-visible and nuclear magnetic resonance spectroscopy) and spectrometric (mass spectrometry) techniques.