Estudo de metabólitos secundários das folhas de Galianthe thalictroides (Rubiaceae)

Abstract

The investigation of natural products remains an essential strategy for the discovery of new bioactive molecules, particularly within the context of Brazilian biodiversity. In this scenario, the present study focused on the phytochemical investigation of the leaves of Galianthe thalictroides (K. Schum.) E. L. Cabral (Rubiaceae), a shrubby species with restricted distribution in South America and traditionally used in folk medicine. The ethanolic extract of the leaves was subjected to systematic extraction, fractionation, and purification procedures, which resulted in the isolation of three β-carboline alkaloids. The structural characterization of these substances was carried out through integrated techniques of one- and two-dimensional NMR, UV-Vis and infrared spectroscopy, as well as high-resolution mass spectrometry (HR-ESI-MS). Among the isolated compounds, two revealed an unprecedented architecture, formed by the association of monoterpene portions with flavan-3-ol (epicatechin) units, constituting a new class of β-carboline–flavonoid hybrid alkaloids. This structural originality confers uniqueness to the species and significantly expands the knowledge about the chemical diversity of the Rubiaceae family. In addition to their novelty, such molecules present potential for future bioactivity studies, given the previously reported cytotoxic and antimicrobial activities for alkaloids of this class. The results obtained confirm the relevance of G. thalictroides as a promising source of structurally complex and biologically relevant secondary metabolites, reinforcing the importance of valuing the flora of the Brazilian Cerrado as a chemical and biotechnological heritage.