Estudo fitoquímico e atividade citotóxica in vitro das partes aéreas da espécie Baccharis oblongifolia.

Abstract

The genus Baccharis (Asteraceae) stands out with approximately 500 species distributed throughout the North and South American continents, with 187 species described in Brazil. It is widely used in folk medicine in the form of teas and infusions for gastrointestinal disorders, inflammations, ulcers, as analgesic, spasmolytic, antimicrobial, among other actions. The species Baccharis oblongifolia, after cytotoxic screening against the A549 cell line, showed promise, and its phytochemical and biological activity study was carried out. Extraction by percolation followed by bioassay-guided fractionation (Fr. Hex, Fr. DCM, Fr. AcOEt, and Fr. MeOH/H2O) was performed against the A549 cell line, and dereplication was done by UPLC-MS/MS. The putative presence of dicaffeoylquinic and tricaffeoylquinic acids and a methoxylated flavanone was identified. The MeOH/H2O fraction was the most active (IC50 = 8.31 ± 0.33) and underwent enrichment by Sephadex column, obtaining a fraction rich in saponins (Fr. SapB). Subsequent attempts at isolation were unsuccessful due to the low stability of saponins during the chromatographic processes employed. Fr. SapB was evaluated by 1D and 2D NMR, UPLC-MS/MS, and GC-MS, and subjected to cytotoxic activity testing against the A549, HepG2, Caco-2 cell lines, and non-tumoral human fibroblast cell line. Fr. SapB was more active and selective against the HepG2 cell line (IC50= 5.35 ± 0.43)/(SI= 7.38). GC-MS analyses demonstrated the presence of the sugars xylose, arabinose, rhamnose, glucose, and residues of galactose. By UPLC-MS/MS, a mass equal to 1572 g/mol of a saponin was identified in Fr. 21 purified by open silica column. The mass of the triterpene core observed was 504 g/mol. In the 1D and 2D NMR spectra of the mixture, a main triterpene core known as 2β,3β,16α,23-tetrahydroxyolean-12-ene-28-oic acid (polygalacic acid) with 7 partially identified monosaccharide units was identified, two units at C-3β-OH linked by a glycosidic bond and five units at C-28 linked by an ester bond, with 3-O-β-xylopyranosyl-(12)-β-glucopyranosyl and only two sugars identified at C-28 as 28-O-α-rhamnopyranosyl-(1 2)-β-arabinopyranosyl.