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Pressurised Fluid Extraction of Bioactive Species in Tree Barks: Analysis using Hyphenated Electrochemical Mass Spectrometric Detection
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
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. , p. 82
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 789
Keywords [en]
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: urn:nbn:se:uu:diva-133264ISBN: 978-91-554-7951-0 (print)OAI: oai:DiVA.org:uu-133264DiVA, id: diva2:360760
Public defence
2010-12-17, B22, Husargatan 3, Uppsala, 10:15 (English)
Opponent
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: 2018-01-12Bibliographically approved
List of papers
1. Pressurized liquid extraction of betulin and antioxidants from birch bark
Open this publication in new window or tab >>Pressurized liquid extraction of betulin and antioxidants from birch bark
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2009 (English)In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 11, no 5, p. 668-674Article in journal (Refereed) Published
Abstract [en]

Pressurized hot (subcritical) water and ethanol were used to extract betulin and antioxidants from birch bark. Betulin was found to be the major compound (around 26% (w/w)), which was able to be extracted with ethanol (120 degrees C, 50 bar, 15 minutes) but not with water at any of the temperatures tested (40-180 degrees C, 50 bar). The obtained extraction result for betulin is supported by theoretical solvation parameter calculations. Furthermore, high antioxidant activity of the extract was obtained using both ethanol and water as solvent. The antioxidant activity, as determined by a DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, was found to be highest for the water extract of finely ground bark and it markedly increased with elevated extraction temperatures (90-180 degrees C). To elucidate if this was due to increased extraction efficiency or chemical reactions, a set of experiments was performed in which the samples were pre-treated with water at different temperatures before extraction. Results from liquid chromatography showed some differences in molecular composition between samples pre-treated at ambient and 180 degrees C, respectively. However, more detailed studies have to be performed to distinguish between hot-water extraction and reaction kinetics.

Place, publisher, year, edition, pages
The Royal Society of Chemistry, 2009
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-106795 (URN)10.1039/b819965e (DOI)000266004400012 ()
Available from: 2009-07-03 Created: 2009-07-03 Last updated: 2017-12-13Bibliographically approved
2. Extraction of Antioxidants from Spruce (Picea abies) Bark using Eco-Friendly Solvents
Open this publication in new window or tab >>Extraction of Antioxidants from Spruce (Picea abies) Bark using Eco-Friendly Solvents
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2012 (English)In: Phytochemical Analysis, ISSN 0958-0344, E-ISSN 1099-1565, Vol. 23, no 1, p. 1-11Article in journal (Refereed) Published
Abstract [en]

Introduction-Antioxidants are known to avert oxidation processes and they are found in trees and other plant materials. Tree bark is a major waste product from paper pulp industries; hence it is worthwhile to develop an extraction technique to extract the antioxidants.

Objective- To develop a fast and environmentally sustainable extraction technique for the extraction of antioxidants from bark of spruce (Picea abies) and also to identify the extracted antioxidants that are abundant in spruce bark.

Methodology- A screening experiment that involved three different techniques, was conducted to determine the best technique to extract antioxidants.The antioxidant capacity of the extracts was determined with DPPH (2,2-diphenyl-2’-picrylhydrazyl) assay. Pressurised fluid extraction (PFE) turned out to be the best technique and a response surface design was therefore utilised to optimise PFE. Furthermore, NMR and HPLC-DAD-MS/MS were applied to identify the extracted antioxidants.

Results- PFE using water and ethanol as solvent at 160 and 180°C, respectively, gave extracts of the highest antioxidant capacity. Stilbene glucosides such as isorhapontin, piceid and astringin were identified in the extracts.

Conclusion-The study has shown that PFE is a fast and environmentally sustainable technique, using water and ethanol as solvent for the extraction of antioxidants from spruce bark.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2012
Keywords
Accelerated solvent extraction, antioxidant, DPPH, ethanol, Picea abies, pressurised fluid extraction, supercritical fluid extraction, water
National Category
Other Basic Medicine
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-133267 (URN)10.1002/pca.1316 (DOI)000298260100001 ()
Funder
Swedish Research Council
Available from: 2010-11-04 Created: 2010-11-04 Last updated: 2018-01-12Bibliographically approved
3. Identification and Characterization of Polyphenolic Antioxidants Using On-Line Liquid Chromatography, Electrochemistry, and Electrospray Ionization Tandem Mass Spectrometry
Open this publication in new window or tab >>Identification and Characterization of Polyphenolic Antioxidants Using On-Line Liquid Chromatography, Electrochemistry, and Electrospray Ionization Tandem Mass Spectrometry
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2009 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 21, p. 8968-8977Article in journal (Refereed) Published
Abstract [en]

It is demonstrated that electrochemistry (EC) coupled to liquid chromatography (LC) and electrospray ionization tandem mass spectrometry (LC/EC/ESI-MS/MS) can be used to rapidly obtain information about the antioxidant activity (i.e., oxidation potential) and capacity (i.e., amount) of polyphenolic compounds, including catechin, kaempferol, resveratrol, quercetin, and quercetin glucosides. The described on-line LC/EC/ESI-MS/MS method facilitates the detection and characterization of individual antioxidants based on a combination of the obtained m/z values for the antioxidants and their oxidation products, the potential dependences for the ion intensities, and correlations between the retention times in the LC, EC, and MS chromatograms. As these results provide patterns that can be used in rapid screening for antioxidants in complex samples, the method should be a valuable complement to chemical assays commonly used to determine the total antioxidant capacity of samples. It is shown that the antioxidant capacity for a mixture of polyphenolic compounds depends on the redox potential employed in the evaluation, and this should consequently be taken into account when comparing results from different total antioxidant capacity assays. It is also demonstrated that the inherent antioxidant capacities of phenolic compounds increase with an increasing number of hydroxyl groups and that the potential needed to oxidize the remaining hydroxyl groups increases successively upon oxidation of the compound. Unlike chemical assays, which generally do not provide any information about the identities of the compounds on the molecular level, the present screening method can be used to identify individual antioxidants, rank compounds with respect to their ease of oxidation, and to study the antioxidant capacity at any redox potential of interest.

National Category
Analytical Chemistry Inorganic Chemistry
Research subject
Analytical Chemistry; Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-99328 (URN)10.1021/ac901397c (DOI)000276191900046 ()
Available from: 2009-03-12 Created: 2009-03-12 Last updated: 2018-06-26Bibliographically approved
4. Degradation effects in the extraction of antioxidants from birch bark using water at elevated temperature and pressure
Open this publication in new window or tab >>Degradation effects in the extraction of antioxidants from birch bark using water at elevated temperature and pressure
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2012 (English)In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 716, p. 40-48Article 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.

 

Keywords
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:nbn:se:uu:diva-132344 (URN)10.1016/j.aca.2011.04.038 (DOI)000301092900008 ()
Available from: 2010-11-04 Created: 2010-10-18 Last updated: 2017-12-12Bibliographically approved

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