Supercritical carbon dioxide extraction of chamomile flowers: extraction efficiency, stability, and in‐line inclusion of chamomile–carbon dioxide extract in β‐cyclodextrin

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Abstract
The extraction of chamomile flowers using supercritical carbon dioxide was investigated with respect to extraction efficiency and compared with solvent extraction. The stability of matricine, a sensitive constituent of the essential oil of chamomile, in these extracts was studied during storage at different temperatures over 6 months. Matricine was stable at −30°C. A slight decrease (80–90% recovery) occurred at +5°C, whereas complete decomposition of matricine took place within 3–4 months at room temperature and at +30°C, respectively. An in‐line inclusion of chamomile constituents in β‐cyclodextrin (β‐CD) during the extraction process was assessed and inclusion rates between 40 and 95% were obtained depending on the amount of β‐CD and the type of chamomile constituent. No further stabilization of matricine in the carbon dioxide extract/β‐CD complexes was achieved. High residual water contents in the complexes even after freeze‐drying were identified as accelerating the decomposition. In addition, the extractability of flavonoids, such as apigenin and apigenin‐7‐glucoside, was determined. Apigenin‐7‐glucoside, the more hydrophilic substance, was not extractable with pure carbon dioxide and showed a recovery of 11% using methanol modified carbon dioxide (18%, w/w) at 60°C and 380 bar. Extraction conditions in the two‐phase region of the binary mixture carbon dioxide–methanol (70°C, 100 bar) led to a drastic change in fluid polarity and hence extractability increased to 92–95%. Copyright © 2004 John Wiley & Sons, Ltd.