Isolamento e identificação de alcaloides piperidínicos minoritários presentes nas flores de Senna spectabilis (Fabaceae)

Abstract

Senna spectabilis belongs to the Fabaceae family and is popularly known as cassia. This species is widely used in urban landscaping and is considered an important source of specialized metabolites, particularly the major piperidine alkaloids (–)-cassine and (–)-spectaline. These compounds have attracted scientific interest due to their acetylcholinesterase inhibitory activity, an enzyme associated with Alzheimer’s disease. Previous studies have reported the occurrence of epimers of (–)-cassine and (–)-spectaline at C-6 of the piperidine ring, known as 6-iso-cassine and 6-iso-spectaline. The investigation of these diastereomers is relevant because changes in stereochemistry may result in different physicochemical properties and potentially affect their biological activities. Therefore, this study aimed to expand the knowledge of the piperidine alkaloids present in S. spectabilis, focusing on the isolation and identification of minor metabolites. Chromatographic techniques, including thin-layer chromatography (TLC), column chromatography (CC), high-performance liquid chromatography (HPLC), and gas chromatography with flame ionization detection (GC-FID), were employed for the separation of the compounds. The isolated metabolites were identified by mass spectrometry (MS) and 1H nuclear magnetic resonance spectroscopy (1H NMR). The results demonstrated that S. spectabilis is an important source of specialized metabolites, whose separation required the application of advanced analytical techniques, particularly HPLC-MS and GC-FID. The isolated diastereomers and homologues provide a basis for future studies aimed at determining the absolute stereochemistry of their stereogenic centers, as well as evaluating their biological activities and elucidating their mechanisms of action.