Estudo fitoquímico e farmacológico de Ruehssia caatingae (Morillo) F. Esp. Santo & Rapini (Apocynaceae) com avaliação in vitro das atividades anti inflamatória e citotóxica

Abstract

The Apocynaceae family comprises approximately 5,350 species distributed across 378 genera, with widespread occurrence in tropical and subtropical regions. In Brazil, the family includes approximately 94 genera and 974 species, including shrubs, trees, herbs, and lianas. Among these is Ruehssia caatingae, a shrubby plant characteristic of Brazil's semiarid region, widely distributed on rocky outcrops in the Caatinga. Until the completion of this study, there were no records of phytochemical or pharmacological investigations of this species. Therefore, this study aimed to expand chemical and pharmacological knowledge of the Apocynaceae family by isolating and characterizing secondary metabolites from the aerial parts (leaves and branches) and roots of R. caatingae, as well as evaluating their cytotoxic and anti-inflammatory activities. For this study, the aerial parts and roots of R. caatingae were collected in the municipality of Pocinhos, Paraíba. The aerial parts and roots were dried and ground separately and subjected to maceration with 95% ethanol for 72 hours, this process being repeated four times, obtaining the crude ethanolic extracts (CEE). The CEE of the aerial parts (28 g) was subjected to Partition Chromatography using the solvents hexane, chloroform, ethyl acetate and n-butanol. The n-butanolic and ethyl acetate phases were subjected to successive fractionation steps using Sephadex LH-20 Chromatography, Medium Pressure Chromatography and High Performance Liquid Chromatography (HPLC), resulting in the isolation of three compounds: 3-methyl-N-pentanoic acid-β-D-galactofuranoside, described for the first time in the literature; (-)-conduritol F, isolated for the first time in the genus; and thymidine, isolated for the first time in the family Apocynaceae. The isolated compounds were evaluated for their cytotoxic potential against the U87-MG, SH-SY5Y, and MDA-MB-231 cell lines, showing no significant cytotoxic activity. The CEE from the roots was subjected to a partition process as previously described. The chloroform phase was subjected to successive fractionation steps by Sephadex LH-20 chromatography, column chromatography and HPLC, resulting in the isolation of eighteen new

pregnane glycosides named Ruehssioside A-R. These compounds were evaluated for their anti- inflammatory potential in activated macrophage models, showing anti-inflammatory activity

by significantly inhibiting the production of IL-1β, IL-6 and nitric oxide. Among them, Ruehssioside J stood out for having the highest potency (IC50 = 17.5 μM). The structure-activity relationship highlighted the importance of substitutions at C-3 and C-20, as well as the presence of a hydrogen at C-8, as determining factors for potency and efficacy. This work expands the chemical and pharmacological knowledge of the Apocynaceae family, highlighting the isolation of new compounds, particularly pregnane glycosides, demonstrating the family's relevance as a source of unique and biologically active structural metabolites.