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Recovery of juçara (Euterpe edulis Mart.) agroindustrial residue: a study of different extraction techniques of phenolic compounds and anthocyanins using high pressure

Author: Maria del Pilar Garcia Mendoza (2016)

Abstract: Nowadays, there is a large interest in finding new sources of natural pigments to make diet more functional and healthy by their consumption. Juçara (Euterpe edulis Mart.), a fruit from the Brazilian rainforest, has attracted the attention of researchers for its content of bioactive compounds with several health benefits Among these compounds there are the anthocyanins, which are antioxidant compounds responsible for the color of many plant species, and are known for their sequestering properties of free radicals that produce degenerative action on the human organism. The industrial processing of juçara generates residues with no commercial value, which have been treated as environmental contaminants. In this context, the aim of this work was to obtain extracts rich in phenolic compounds and anthocyanins from industrial residues of juçara (Euterpe edulis Mart), using different high pressure extraction processes, in order to evaluate their functional potential. For this purpose, Pressurized Liquid Extraction (PLE) with different solvents (ethanol, acidified mixture (pH 2.0) of ethanol + water 50% v:v, water and acidified water pH 2.0) at different temperatures (40, 60 e 80 oC), fixing the pressure (10 MPa) and the solvent to feed mass ratio S/F = 24 kg solvent/kg residue). It was also performed a Soxhlet extraction and a sequential PLE procedure, to obtain fractionated extracts rich in target compounds. All extractions were evaluated in terms of Total Phenolic Content (TPC), Monomeric Anthocyanin Content (MAC) and Antioxidant Activity (AAt) by DPPH method according to the process variables (temperature and solvent type). Subsequently, it was selected the best solvent of PLE in terms of TPC, MAC and AAt to be evaluated as cosolvent for supercritical fluid extraction (SFE) (20 MPa, 60 °C, 10% CO2 – 10% cosolvent), as well as in low pressure extractions (agitated bed and assisted by ultrasound). The results showed that the best solvent of PLE was the acidified mixture (pH 2.0) of ethanol + water 50% v:v. Anthocyanins present in all extracts were identified and quantified by ultra performance liquid chromatography (UPLC-Ultra Performance Liquid Chromatography) coupled to mass spectrometry (UPLC-QToF -MS). For all experiments a statistical comparison was performed through the Tukey test, by analysis of variance (ANOVA) at a significance level of 5%. The results showed that the highest TPC (51.34 mg GAE/g dry residue) was obtained by the acidified mixture of ethanol + water 50% v:v at 80 °C and the highest MAC (9.75 mg C3RE/g dry residue) was achieved with acidified water at 40 °C. The increase of temperature had negative effect on the anthocyanin recovery, due to their instability, however TPC was improved when temperature increased. It was also observed that TPC showed a positive correlation with the antioxidant activity of the extracts. The UPLC-QToF-MS analysis showed that the major anthocyanins in the extracts were cyanidin-3-rutinoside (C3R) and cyanidin-3-glucoside (C3G), while the minor were peonidin-3-rutinoside (Peo3R) and peonidin-3-glucoside (Peo3Gl). The selected cosolvent for SFE improved significantly the anthocyanins content (21.83 mg C3RE/g dry residue). Therefore, high pressure technologies achieve satisfactory results and suggest a great potential for the application of juçara residues to obtain extracts with high added value.