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Antioxidant activity of fractions from Quercus sideroxyla bark and identifi cation of proanthocyanidins by HPLC-DAD and HPLC-MS

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  • The most active phenolics in Quercus sideroxyla Humb. & Bonpl. residual bark were identified and evaluated following a chromatographic fractionation. Bark powder was defatted with hexane and crude extract (CE) was obtained by extraction with aqueous acetone (70%). A liquid partition with ethyl acetate was performed to produce an organic extract (OE), which was subsequently purified by column chromatography (Toyopearl HW-40F, methanol), and resulted in six methanolic fractions (MF1 to MF6) and an oligomeric fraction (OLF) eluted with acetone 67%. Extraction yields, total phenolic and flavanol contents were determined. The antioxidant activity of bark extracts was measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH), Trolox (6-hydroxy-2,5,7,8-tetramethyl-chroman-2-carboxylic-acid)-equivalent antioxidant capacity (TEAC), and ferric ion reducing antioxidant power (FRAP) assays. Their median effective concentration (EC₅₀) data and rate constants for DPPH radical scavenging were also estimated. Identification of major phenolics was carried out by high performance liquid chromatography with diode array detection (HPLC-DAD) and high performance liquid chromatography with electrospray ionization coupled to mass spectrometry (HPLC-ESI-MS) instruments. Bioactive gallic acid, catechin, epicatechin, gallocatechin, catechin gallate, dimeric procyanidins, galloylated dimeric proanthocyanidins, trimeric procyanidins, and tetrameric proanthocyanidins were detected and identified in Q. sideroxyla bark extracts. MF2 was the most active fraction containing gallocatechin as its major compound; MF5 and OLF contain galloylated procyanidins, which may explain their higher antiradical activity. OLF besides galloylated procyanidins has gallocatechin, which presumably contributes to its higher antiradical activity. Consequently, Q. sideroxyla bark could be a good source of therapeutic health products or nutraceutical ingredients that may exert a potential prevention or treatment action against diseases in biological systems.
  • This is the publisher’s final pdf. The published article is copyrighted by Walter de Gruyter and can be found at: http://www.degruyter.com/view/j/hfsg.
  • Keywords: proanthocyanidins, Quercus sideroxyla ., bark, antiradical activity, HPLC
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  • Rosales-Castro, M., Gonzalez-Laredo, R., Rocha-Guzman, N., Gallegos-Infante, J., Rivas-Arreola, M., & Karchesy, J. (2012). Antioxidant activity of fractions from quercus sideroxyla bark and identification of proanthocyanidins by HPLC-DAD and HPLC-MS. HOLZFORSCHUNG, 66(5), 577-584. doi: 10.1515/hf-2011-0157
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  • 65
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  • 5
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  • Author MRC appreciates doctoral scholarship from CONACYT México. This study was financially supported by Fondo Sectorial CONAFOR-CONACYT, México (2006-41839).
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