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Degradation effects in the extraction of antioxidants from birch bark using water at elevated temperature and pressure
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
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2012 (English)In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 716, 40-48 p.Article in journal (Refereed) Published
Abstract [en]

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.

 

Place, publisher, year, edition, pages
2012. Vol. 716, 40-48 p.
Keyword [en]
Degradation, Pressurised fluid extraction, Antioxidants, DPPH assay, Electrochemical detection, Diode-array detection, Tandem mass spectrometry, Elevated temperature, Birch bark
National Category
Inorganic Chemistry
Research subject
Analytical Chemistry; Chemistry with specialization in Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-132344DOI: 10.1016/j.aca.2011.04.038ISI: 000301092900008OAI: oai:DiVA.org:uu-132344DiVA: diva2:360742
Available from: 2010-11-04 Created: 2010-10-18 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Pressurised Fluid Extraction of Bioactive Species in Tree Barks: Analysis using Hyphenated Electrochemical Mass Spectrometric Detection
Open this publication in new window or tab >>Pressurised Fluid Extraction of Bioactive Species in Tree Barks: Analysis using Hyphenated Electrochemical Mass Spectrometric Detection
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Analytical chemistry has developed throughout time to meet current needs. At present, the interest in biorefinery is growing, due to environmental awareness and the depletion of fossil resources. Biomass from agricultural and forestry industries has proven to be excellent raw material for different processes. Biorefinering valuable species such as bioactive species from biomass, without compromising the primary process of the biomass is highly desirable. Pressurised fluid extraction (PFE) using water and ethanol as a solvent was developed for extracting betulin from birch (Betula pendula) bark. Apart from betulin, stilbene glucosides such as astringin, isorhapontin and picied were also extracted from spruce (Picea abies) using PFE. PFE is an advanced technique that extracts at temperatures above the solvent’s atmospheric boiling point. The applied pressure in PFE is mainly to maintain the liquid state of the extraction solvent. Parameters such as type of solvent, temperature, and time affect the extraction selectivity and efficiency. Therefore it is necessary to comprehend these parameters in order to optimise extraction. The DPPH (1,1-diphenyl-2-picrylhydrazyl) assay was used to determine the antioxidant capacity and activity of the obtained bioactive species. The results showed high antioxidant capacity in bioactive species that were extracted at an elevated temperature, 180°C. Extraction and degradation occur simultaneously during the extraction. Hence, it is crucial to separate these two processes in order to obtain the actual value.

An online hyphenated system of chromatographic separation electrochemical mass spectrometric detection was developed (LC-DAD-ECD-MS/MS). The electrochemical detector facilitates real-time monitoring of the antioxidant capacity and activity of each antioxidant and its oxidation products. This developed LC-DAD-ECD-MS/MS method enabled rapid screening of antioxidants and created a fingerprint map for their oxidation products. Characterisation and molecular elucidation of bioactive species were also performed. Degradation of bioactive species was investigated with the said online system and birch bark extract was compared with birch bark extracts that were hydrothermally treated. The obtained results showed some degradation of antioxidants at 180°C.

In summary, the aim of this thesis was to develop analytical methods integrated with sustainable chemistry for extraction of bioactive species in biomass from the forestry industry. A novel online system using selective and sensitive detectors such as diode-array, electrochemical, and tandem mass spectrometry was developed to rapidly determine the antioxidant capacity and activity of antioxidants. Furthermore, tandem mass spectrometry enables identification of unknown bioactive species without the need of reference samples.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 82 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 789
Keyword
Pressurised fluid extraction, antioxidants, DPPH, water, ethanol, antioxidant activity, antioxidant capacity, electrochemial detection, mass spektrometry
National Category
Other Basic Medicine
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-133264 (URN)978-91-554-7951-0 (ISBN)
Public defence
2010-12-17, B22, Husargatan 3, Uppsala, 10:15 (English)
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Supervisors
Note
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 719Available from: 2010-11-26 Created: 2010-11-04 Last updated: 2011-05-10Bibliographically approved

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Nyholm, LeifSjöberg, Per J.R

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