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Antioxidant Activity of Lignin Phenolic Compounds Extracted from Kraft and Sulphite Black Liquors
Textile & Paper Materials Research Unit, University of Beira Interior, 6201-001 Covilhã, Portugal
Department of Chemical and Environmental Engineering, ESTT, Polytechnic Institute of Tomar, 2300-313 Tomar, Portugal
Faculty of Health Sciences, University of Beira Interior, 6201-001 Covilhã, Portugal
Faculty of Health Sciences, Health Sciences Research Centre, 6201-001 Covilhã, Portugal
* Author to whom correspondence should be addressed.
Received: 19 October 2010; in revised form: 13 December 2010 / Accepted: 14 December 2010 / Published: 16 December 2010
Abstract: The antioxidant activity of the phenolic compounds present in industrial black liquors obtained from the two cooking processes (kraft and sulphite) used in Portugal to produce Eucalyptus globulus pulp was evaluated. The black liquors treated at several pH values were extracted with ethyl acetate. Phenolic fractions were further separated by liquid chromatography of the crude extracts of kraft liquor at pH = 6 and sulphite liquor at the original pH. Total phenolic content was determined in terms of gallic acid equivalents (Folin-Ciocalteu colorimetric method), and the antioxidant activity in the crude extracts at several pH values and in the separated fractions was measured using the DPPH test for radical scavenging capacity. The total phenolic content of crude extracts and separated fractions ranged from 92.7 to 181.6 and from 91.6 to 1,099.6 mg GAE/g, respectively, while the antioxidant activity index (AAI) ranged from 2.20 to 3.41 and from 2.21 to 11.47 respectively, showing very strong antioxidant activity in all studied cases. The fractions separated by column chromatography were submitted to mass spectrometry analysis and the results were compared to others in the literature of natural products, mainly from Eucalyptus, and the characteristic bands of functional groups were identified by 1H-NMR and FTIR. These methods allowed the identification of 17 phenolic compounds.
Keywords: Eucalyptus globulus; antioxidant activity; black liquors; DPPH method; total phenolic content
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MDPI and ACS Style
Faustino, H.; Gil, N.; Baptista, C.; Duarte, A.P. Antioxidant Activity of Lignin Phenolic Compounds Extracted from Kraft and Sulphite Black Liquors. Molecules 2010, 15, 9308-9322.
Faustino H, Gil N, Baptista C, Duarte AP. Antioxidant Activity of Lignin Phenolic Compounds Extracted from Kraft and Sulphite Black Liquors. Molecules. 2010; 15(12):9308-9322.
Faustino, Hélio; Gil, Nuno; Baptista, Cecília; Duarte, Ana Paula. 2010. "Antioxidant Activity of Lignin Phenolic Compounds Extracted from Kraft and Sulphite Black Liquors." Molecules 15, no. 12: 9308-9322.