Triterpene compounds like betulin, betulinic acid, erythrodiol, oleanolic acid and lupeol\nare known for many pharmacological effects. All these substances are found in the outer bark of\nbirch. Apart from its pharmacological effects, birch bark extract can be used to stabilise semisolid\nsystems. Normally, birch bark extract is produced for this purpose by extraction with organic solvents.\nEmploying supercritical fluid technology, our aim was to develop a birch bark dry extract suitable\nfor stabilisation of lipophilic gels with improved properties while avoiding the use of toxic solvents.\nWith supercritical carbon dioxide, three different particle formation methods from supercritical\nsolutions have been tested. First, particle deposition was performed from a supercritical solution in\nan expansion chamber. Second, the Rapid Expansion of Supercritical Solutions (RESS) method was\nused for particle generation. Third, a modified RESS-procedure, forming the particles directly into the\nthereby gelated liquid, was developed. All three methods gave yields from 1% to 5.8%, depending\non the techniques employed. The triterpene composition of the three extracts was comparable:\nall three gave more stable oleogels compared to the use of an extract obtained by organic solvent\nextraction. Characterizing the rheological behaviour of these gels, a faster gelling effect was seen\ntogether with a lower concentration of the extract required for the gel formation with the supercritical\nfluid (SCF)-extracts. This confirms the superiority of the supercritical fluid produced extracts with\nregard to the oleogel forming properties.
Loading....