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Degradation effects in the extraction of antioxidants from birch bark using water at elevated temperature and pressure

Co, Michelle; Zettersten, Camilla; Nyholm, Leif; Sjoberg, Per J. R. and Turner, Charlotta LU (2012) In Analytica Chimica Acta 716. p.40-48
Abstract
Experiments with birch bark samples have been carried to enable a distinction between extraction and degradation effects during pressurised hot water extraction. Two samples, E80 and El 80, contained birch bark extracts obtained after extraction at 80 and 180 degrees C for up to 45 min, respectively. Two other samples, P80 and P180, were only extracted for 5 min at the two temperatures and were thereafter filtered and hydrothermally treated at 80 and 180 degrees C, respectively. During the latter treatment, samples were collected at different times to assess the stability of the extracted compounds. An offline DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, as well as a high performance liquid chromatographic separation coupled to an... (More)
Experiments with birch bark samples have been carried to enable a distinction between extraction and degradation effects during pressurised hot water extraction. Two samples, E80 and El 80, contained birch bark extracts obtained after extraction at 80 and 180 degrees C for up to 45 min, respectively. Two other samples, P80 and P180, were only extracted for 5 min at the two temperatures and were thereafter filtered and hydrothermally treated at 80 and 180 degrees C, respectively. During the latter treatment, samples were collected at different times to assess the stability of the extracted compounds. An offline DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, as well as a high performance liquid chromatographic separation coupled to an electrochemical detector, were used to determine the antioxidant capacity of the processed samples. The results obtained with the different techniques were compared to assess the yield of the extraction and degradation processes. In addition, an online hyphenated system comprising high performance liquid chromatography coupled to diode-array; electrochemical; and tandem mass spectrometric detection (HPLC-DAD-ECD-MS/MS) was used to study the compositions of the extracts in more detail. The results for the samples processed at 80 degrees C showed that the extraction reached a steady-state already after 5 min, and that the extracted compounds were stable throughout the entire extraction process. Processing at 180 degrees C, on the other hand, gave rise to partly degraded extracts with a multitude of peaks in both the diode array and electrochemical detectors, and a higher antioxidant capacity compared to for the extracts obtained at 80 degrees C. It is concluded that HPLC-DAD-ECD is a more appropriate technique for the determination of antioxidants than the DPPH assay. The mass spectrometric results indicate that one of the extracted antioxidants, catechin, was isomerised to its diastereoisomers; (+)-catechin, (-)-catechin, (+)-epicatechin, and (-)-epicatechin. (C) 2011 Elsevier B.V. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Birch bark, spectrometry, Elevated temperature, Antioxidants, DPPH assay, Electrochemical detection, Diode-array detection, Tandem mass, Pressurised fluid extraction, Degradation
in
Analytica Chimica Acta
volume
716
pages
40 - 48
publisher
Elsevier
external identifiers
  • wos:000301092900008
  • scopus:84856218090
ISSN
1873-4324
DOI
10.1016/j.aca.2011.04.038
language
English
LU publication?
yes
id
92cbefba-f497-4d0b-8fc2-1d8f3aa2e3de (old id 2517339)
date added to LUP
2012-05-09 09:51:46
date last changed
2017-01-01 06:17:39
@article{92cbefba-f497-4d0b-8fc2-1d8f3aa2e3de,
  abstract     = {Experiments with birch bark samples have been carried to enable a distinction between extraction and degradation effects during pressurised hot water extraction. Two samples, E80 and El 80, contained birch bark extracts obtained after extraction at 80 and 180 degrees C for up to 45 min, respectively. Two other samples, P80 and P180, were only extracted for 5 min at the two temperatures and were thereafter filtered and hydrothermally treated at 80 and 180 degrees C, respectively. During the latter treatment, samples were collected at different times to assess the stability of the extracted compounds. An offline DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, as well as a high performance liquid chromatographic separation coupled to an electrochemical detector, were used to determine the antioxidant capacity of the processed samples. The results obtained with the different techniques were compared to assess the yield of the extraction and degradation processes. In addition, an online hyphenated system comprising high performance liquid chromatography coupled to diode-array; electrochemical; and tandem mass spectrometric detection (HPLC-DAD-ECD-MS/MS) was used to study the compositions of the extracts in more detail. The results for the samples processed at 80 degrees C showed that the extraction reached a steady-state already after 5 min, and that the extracted compounds were stable throughout the entire extraction process. Processing at 180 degrees C, on the other hand, gave rise to partly degraded extracts with a multitude of peaks in both the diode array and electrochemical detectors, and a higher antioxidant capacity compared to for the extracts obtained at 80 degrees C. It is concluded that HPLC-DAD-ECD is a more appropriate technique for the determination of antioxidants than the DPPH assay. The mass spectrometric results indicate that one of the extracted antioxidants, catechin, was isomerised to its diastereoisomers; (+)-catechin, (-)-catechin, (+)-epicatechin, and (-)-epicatechin. (C) 2011 Elsevier B.V. All rights reserved.},
  author       = {Co, Michelle and Zettersten, Camilla and Nyholm, Leif and Sjoberg, Per J. R. and Turner, Charlotta},
  issn         = {1873-4324},
  keyword      = {Birch bark,spectrometry,Elevated temperature,Antioxidants,DPPH assay,Electrochemical detection,Diode-array detection,Tandem mass,Pressurised fluid extraction,Degradation},
  language     = {eng},
  pages        = {40--48},
  publisher    = {Elsevier},
  series       = {Analytica Chimica Acta},
  title        = {Degradation effects in the extraction of antioxidants from birch bark using water at elevated temperature and pressure},
  url          = {http://dx.doi.org/10.1016/j.aca.2011.04.038},
  volume       = {716},
  year         = {2012},
}