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Appl. Sci. 2017, 7(3), 292; doi:10.3390/app7030292

Birch Bark Dry Extract by Supercritical Fluid Technology: Extract Characterisation and Use for Stabilisation of Semisolid Systems

1
Department of Pharmaceutical Technology, Auf der Morgenstelle 8, 72076 Tübingen, Germany
2
Department of Pharmaceutics and Biopharmaceutics, Grasweg 9a, 24118 Kiel, Germany
*
Author to whom correspondence should be addressed.
Academic Editor: Jose Augusto Paixao Coelho
Received: 31 December 2016 / Revised: 1 March 2017 / Accepted: 3 March 2017 / Published: 16 March 2017
(This article belongs to the Special Issue The Applications of Supercritical Carbon Dioxide)
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Abstract

Triterpene compounds like betulin, betulinic acid, erythrodiol, oleanolic acid and lupeol are known for many pharmacological effects. All these substances are found in the outer bark of birch. Apart from its pharmacological effects, birch bark extract can be used to stabilise semisolid systems. Normally, birch bark extract is produced for this purpose by extraction with organic solvents. Employing supercritical fluid technology, our aim was to develop a birch bark dry extract suitable for stabilisation of lipophilic gels with improved properties while avoiding the use of toxic solvents. With supercritical carbon dioxide, three different particle formation methods from supercritical solutions have been tested. First, particle deposition was performed from a supercritical solution in an expansion chamber. Second, the Rapid Expansion of Supercritical Solutions (RESS) method was used for particle generation. Third, a modified RESS-procedure, forming the particles directly into the thereby gelated liquid, was developed. All three methods gave yields from 1% to 5.8%, depending on the techniques employed. The triterpene composition of the three extracts was comparable: all three gave more stable oleogels compared to the use of an extract obtained by organic solvent extraction. Characterizing the rheological behaviour of these gels, a faster gelling effect was seen together with a lower concentration of the extract required for the gel formation with the supercritical fluid (SCF)-extracts. This confirms the superiority of the supercritical fluid produced extracts with regard to the oleogel forming properties. View Full-Text
Keywords: supercritical carbon dioxide; RESS; birch bark; triterpenes; gel formation; rheology; amplitude sweep supercritical carbon dioxide; RESS; birch bark; triterpenes; gel formation; rheology; amplitude sweep
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Armbruster, M.; Mönckedieck, M.; Scherließ, R.; Daniels, R.; Wahl, M.A. Birch Bark Dry Extract by Supercritical Fluid Technology: Extract Characterisation and Use for Stabilisation of Semisolid Systems. Appl. Sci. 2017, 7, 292.

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