Search

This paper proposes an alternative way to intensify the exploitation of Eucalyptus wood wastes before valorisation for energy production. An aqueous two-phase system (ATPS) based on PEG 2000 and sodium citrate was investigated for the recovery of phenolic compounds that could act as natural antioxidants for applications including cosmetics, pharmaceuticals, food additives and other industrial applications. The influence of the tie line length (TLL) (26,1-46,1%), extraction temperature (25-65°C), extraction time (90-390 min) and phase settlement time (1 -8 h) were studied. Phenolic compounds were concentrated preferentially in the PEG-rich phase. A partition coefficient of 38 and a total phenols yield of 1,29 mg gallic acid equivalent/100 mg wood dry basis were obtained under the operational conditions selected: TLL, 46,1%, temperature 65°C, extraction time 90 min and settlement time 1 h. Analysis of the extracts by RP-HPLC-ESI-TOF confirmed the presence of various phenolic compounds with demonstrated antioxidant activity: monogalloyl glucose, (-)-gallic acid, ellagic acid and quercetin 3-O-rhamnoside. [ABSTRACT FROM AUTHOR]

BACKGROUND Aqueous two-phase extraction is recognized as an effective, versatile and important emerging green-technique for the downstream processing of biomolecules. Extraction of phenolic compounds from trimmings of Eucalyptus globulus wood veneers was studied using aqueous two-phase systems ( ATPS) (water + polymer + salt) based on PEG 2000 and ammonium sulphate. The aim was the recovery of phenolic compounds to be used as natural antioxidants. Experiments were planned to optimize the extraction process. The influence of several operational conditions (time, temperature, ATPS composition, solid-liquid ratio and settlement time) on phenolics recovery was studied. RESULTS It was found that phenolic compounds have preference for the top PEG-rich phase. Settlement time had no significant impact on phase composition. Total phenols yield increased with temperature, extraction time and amount of solvent used. However, ATPS composition did not significantly influence total phenol yield. Extract analysis by RP-HPLC-ESI-TOF confirmed the presence of phenolic compounds with potential antioxidant activity, namely, mono and digalloyl glucose, (−)-gallic acid, ellagic acid and quercetin 3-O-rhamnoside. CONCLUSION Results demonstrated that extraction with ATPS ( PEG 2000 and ammonium sulphate) is an efficient way for recovering phenolics from eucalyptus wastes without requiring previous purification (total phenols yield of up to 1.88 ± 0.04 mg GAE/100 o.d. wood). © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The aim of this work was to study the extraction of phenolic compounds from chestnut bur and shell, both waste products of chestnut processing in the food industry. Two extraction techniques were compared—maceration with solvents and microwave-assisted extraction. The influence of the solvent used (water, 50% MeOH or 50% EtOH) and temperature (25-50-75°C) on extraction yield and extract total phenols content and FRAP, DPPH, and ABTS antioxidant activities was studied. In the conventional extraction, the yield was significantly higher for the bur (8.54–19.58%) than for the shell (2.91–13.27%); however, the shell extracts showed substantially greater properties. The best extract properties were achieved at 75°C using 50% MeOH for the bur and water for the shell and phenolic compounds with demonstrated antioxidant properties, as gallic acid esters of glucose and ellagic acid, were identified in these extracts by RP-HPLC-ESI-TOF. In addition, the aqueous extracts showed ability to inhibit the growth of gram positive and negative bacteria but not fungi. The kinetic of the extraction process was well fitted by the Peleg's model. The non-conventional microwave-assisted extraction slightly improved the chestnut bur extraction by reducing the extraction time. [ABSTRACT FROM PUBLISHER]

The extraction of phenolic compounds from eucalyptus ( Eucalyptus globulus) bark was examined with the aim of analyzing the potential of the extracts as natural antioxidants. Experiments were planned according to a 2 factorial design to analyze the influence of temperature and NaSO and NaOH concentrations in aqueous solutions on extraction yield, extract total phenols content, ferric reducing antioxidant power (FRAP), and number- and weight-average molecular weights. Extract total phenols content and FRAP antioxidant activity in the ranges 0.91-2.58 g gallic acid equivalent (GAE)/100 g oven-dried bark and 4.70-11.96 mmol ascorbic acid equivalent (AAE)/100 g oven-dried bark, respectively, demonstrated the potential of eucalyptus bark as a source of antioxidant compounds. Extraction at the highest temperature (100°C), the lowest NaSO concentration (1.5% on oven-dried bark), and without NaOH provided the highest extract total phenols content and FRAP antioxidant activity. Those eucalyptus bark extracts with lower molecular weight showed higher antioxidant activity. Matrix-assisted laser desorption ionization time-of-flight and reverse-phase high-performance liquid chromatography electrospray ionization time-of-flight mass spectrometry revealed the presence of polygalloyl glucoses, catechin, epicatechin, ellagic acid, quercetin-3-o-rhamnoside, and isorhamnetin in eucalyptus bark aqueous extracts. [ABSTRACT FROM AUTHOR]