Prospecção química de Acnistus arborescens visando à caracterização de vitaesteróides através de Cromatografia Líquida acoplada à Espectrometria de Massas

Abstract

In this study herein, describes the chemical prospect of ethanol extract from leaves of Acnistus arborescens (Solanaceae). Therefore, this study resulted in the isolation and characterization of several secondary metabolites, including the withaphysalins M, N, O, F (epimers 18R and 18S) and 2,3-dehydro-F (epimers 18R and 18S), as well as four new withaphysalins, being three chlorinated. Their structures were established as new withaphysalins: rel-(17S, 20R, 22R)-6-chloro-18S-ethoxy-18,20-epoxy-4,5-dihidroxy-1-oxo-witha-2,24-dienolide, rel-(17S, 20R, 22R)-6-chloro-18R-ethoxy-18,20-epoxy-4,5-dihidroxy-1-oxo-witha-2,24-dienolide, rel-(17S, 20R, 22R)-6α-chloro-18,20-epoxy-4β,5β-dihidroxy-18α-methoxy-1-oxo-whita-2,24-dienolide e rel-(17S,20R,22R)-5β,6β:18,20-diepoxy-3β,18α-diethoxy-4β-hidroxy-1-oxo-witha-24-enolide. Furthermore, two flavonoids, kaempferol and quercetin, were also isolated and a ceramide, whose structure was determined as rel-(2S,3S,4R,16E)-2-[(2’R)-2’-hydroxynonadecanoylamino]-heneicosadec-16-ene-1,3,4-triol. A study was also carried out about fragmentation with withaphysalins isolated with the objective to construct a mini-library with fragmentation patterns, in order to recognize the withaphysalins or similar compounds in other extracts. Hence, it was possible to identify eight new withaphysalins (C-H, J and K) in a fraction of high cytotoxic potential (PPTC38), and perform a qualitative study of the chemical composition in extracts from leaves of A. arborescens, whereby it was possible to identify the withaphysalin F, as a major constituent from the fraction duly analyzed. The analytical techniques used in the structural elucidation of isolated compounds were IR, MSHR and 1H and 13C NMR (1D and 2D), where as the technique used in the study of fragmentation, as well as the qualitative analysis of the fractions, was the liquid chromatography-mass spectrometry high resolution (HPLC-MS).