Estudo fitoquímico dos bulbos de Eleutherine bulbosa (Miller) Urban (Iridaceae)

Abstract

The species Eleutherine bulbosa (Mill.) Urb. is an herbaceous plant belonging to the Iridaceae family, popularly known as "marupazinho." It is native to tropical countries in South America and is also found in Africa and Asia. In Brazil, it is distributed across various biomes, including the Amazon, Cerrado, Atlantic Forest, Pantanal, and Caatinga. Several subclasses of compounds have already been reported in its composition, with special emphasis on the isolation and identification of naphthoquinones, anthraquinones, and naphthalene derivatives in E. bulbosa. This discovery motivated us to continue isolating compounds from this species. In this context, the objective of the present study was to investigate the chemical composition of the bulb using both classical and modern phytochemical approaches. Two extracts (dichloromethane and ethanol) were obtained by maceration at room temperature. After drying and yield calculation, the extracts were subjected to chemical profiling, and the dichloromethane extract (40.0 g) was fractionated by open column chromatography (CC). Among the fractions obtained, some were further purified using preparative thin-layer chromatography (PTLC), precipitation, and successive washings with acetonitrile or hexane, leading to the isolation of five main compounds: the anthraquinone methyl ester of 4,8-dihydroxy-3-methoxy-1-methylanthraquinone-2-carboxylic acid; the anthraquinone methyl ester of 8-hydroxy-3,4-dimethoxy-1-methylanthraquinone-2-carboxylic acid; the naphthalene eleutherol; the naphthoquinone 3-[2-(acetoxy)propyl]-2-hydroxy-8-methoxy-1,4-naphthoquinone; and the naphthoquinone eleutoquinone, proposed as a novel compound. The structural elucidation of the isolated compounds was carried out using nuclear magnetic resonance spectroscopy (¹H and ¹³C NMR – 1D/2D) and mass spectrometry (MS). The results obtained are relevant to the chemotaxonomy of the genus Eleutherine, particularly for the species under study. Furthermore, the isolation of potentially novel compounds highlights the importance of research involving native plant species, opening promising avenues for future investigations into their biological properties.