Chemical composition and antioxidant activity of phenolic extracts of cork from Quercus suber L.

Abstract

The phenolic fraction of cork from Quercus sober L. was obtained following two distinct fractionation schemes, namely methanol/water extraction followed by ethyl ether fractionation and sequential extraction with methanol and water. The extracts were studied in terms of total phenolics content, using Folin-Ciocalteu method, detailed chemical analysis by HPLC-MS. and antioxidant activity. The first method underestimates both total extractives, total phenolics as well as the amounts of identified compounds. The HPLC-MS, revealed that, apart from smaller components, all the extracts displayed the same qualitative composition; 15 phenolic components were identified, with ellagic acid, followed by gallic and protocatechuic acids as the most abundant compounds. Additionally some compounds identified were reported for the first time as cork components, namely salicylic acid, eriodictyol, naringenin, quinic acid and hydroxyphenyllactic acid. The antioxidant activity of the extracts, evaluated using the 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) radical scavenging assay, showed to be considerably higher than that of BHT, and in the range of ascorbic acid. The antioxidant potential per mass unit of the three extracts is in the same range, but the high extraction yields obtained by water extraction open good perspectives for the exploitation of this extract in nutraceutical applications. (C) 2010 Elsevier B.V. All rights reserved.