Constituintes químicos e atividade antioxidante de Roupala paulensis Sleumer (PROTEACEAE)

Abstract

The Proteaceae family is constituted of about 80 genus and 1705 species, with more distribution in Australia, South Africa and South America. In Brazil, consist in 4 genus, and among these we find the Roupala genus, having about 33 species and 2 subspecies. Among the species of this genus we highlight the species Roupala paulensis Sleumer, an endemic species from Brazil that has a greater distribution in the states of Bahia, Ceará, Pernambuco, Rio de Janeiro and São Paulo. This study aimed to realize a phytochemical study of Roupala paulensis and to evaluate the antioxidant activity and perform the quantification of total phenolics of the extract and phases. For this, the plant material was subjected to extraction processes, partition and chromatography to isolate the chemical constituents. The chemical structure of the substances was determined by spectroscopic methods such as Infrared, Nuclear Magnetic Resonance of 1H and 13C, Mass Spectrometry and comparisons with literature data. The chromatographic fractionation (subdivision) of the hexane fraction resulted in the isolation of the triterpene 2,6,10,15,19,23-hexamethyl-2,6,10,14,18,22-tetracosahexene (squalene), of the triterpenes mixture urs-12-en-3β-ol (α-amyrin), olean-12-en-3β-ol (β-amyrin) and 3β-hydroxy-lup-20(29)-ene (lupeol), of the steroid β-sitosterol and of the mixture pheophytins 132-hydroxy-(132-R)-pheophytin a and 132-hydroxy-(132-S)-pheophytin a, of the dichloromethane fraction there was obtained the glycosylated steroid sitosterol-3-O-β-D-glucopyranoside and of the ethyl acetate fraction was isolated the flavone 3,3′,4′,5,7 -pentahydroxyflavone (quercetin). All compounds are being reported for the first time in Roupala genus. The antioxidant activity of ethanol extract and hexane fraction, dichloromethane and ethyl acetate was verified by DPPH free radical assay (2,2-diphenyl-1-picryl-hydrazyl-hydrate) and by quantification of total phenolics, with comparisons of the results obtained with the standards ascorbic acid and gallic acid, respectively. Among all samples tested the extract showed lower EC50 (37.50 ± 0.46 μg/mL), followed by ethyl acetate fraction (74.86 ± 2.73 μg/mL), the samples had higher antioxidant activity. For quantification of total phenolics samples that exhibited higher concentrations of these compounds were the extract (24.27 ± 0.76 gGAE/100 g) and the ethyl acetate fraction (30.47 ± 0.52 gGAE/100 g). Therefore, these samples showed the greatest concentration of phenolic compounds, most likely responsible for the better results presented antioxidant activity in the DPPH assay realized.