Estudo químico e biológico de Palicourea nitidella (Müll.Arg.) Standl

Abstract

Species of the genus Palicourea Aubl. Rubiaceae are rich in secondary metabolites such as iridoids, indole alkaloids, anthraquinones, terpenoids and phenolic compounds, which are interesting for bioprospecting because they have anticancer, anti-inflammatory and antioxidant activities. The objective of this work was to bioprospect the hexane and methanolic extracts of leaves and branches of Palicourea nitidella (Müll.Arg.) Standl. for antimicrobial, antioxidant and toxic activities as well as chemical components of interest. To determine the antioxidant activity, tests were carried out with the DPPH• and Fe3+/phenanthroline methods and extracts at a concentration of 0.5 mg/mL. To evaluate the antimicrobial activity, the microdilution method was applied in broth at a concentration of 1000 µg/mL, against ten microorganisms and the minimum inhibitory concentration was also determined. For toxicity evaluation, Artemia salina was used at concentrations of 1000 and 500 µg/mL. As a result in the test against A. salina, the extracts did not show mortality above 50%. In the antioxidant activity against the DPPH• and Fe3+/phenanthroline methods, the evaluated methanolic extracts showed inactivity. The hexane extracts from the leaves and branches showed antibacterial activity against Pseudomonas fluorescens and Staphylococcus aureus, and the hexane extract from the branches inhibited the growth of Aeromonas hydrophila, Citrobacter freundi, Pseudomonas aeruginosa and Salmonella enteritidis. The active extracts were subjected to chromatographic fractionation and the isolated substances were identified by means of uni and two-dimensional 1H and 13C NMR analysis and mass spectrometry. Thus, the mixture of β-sitosterol and stigmasterol from the hexane extract of leaves and the fractionation of the methanolic extract of branches was obtained to obtain scopoletin. In this work it was found that the hexane extracts were active for six gram-negative and one gram-positive bacteria, as well as three substances were isolated: β-sitosterol, stigmasterol and scopoletin. The results contributed to the chemical characterization and biological potential of P. nitidella.