Analytical and preparative supercritical fluid extraction of chamomile flowers and its comparison with conventional methods.

Supercritical fluid extraction (SFE) was compared with Soxhlet extraction, steam distillation and maceration for the isolation of the active components present in chamomile flowerheads. The obtained fractions were analysed by GC-MS and reversed-phase HPLC. The yield of essential oil achieved by a 30-min extraction with pure CO2 at 90 atm and 40 degrees C was 4.4 times higher than that produced by steam distillation performed for 4 h. The recovery of the flavonoid apigenin obtained by supercritical CO2 after a 30-min extraction at 200 atm and 40 degrees C was 71.4% compared to Soxhlet extraction performed for 6 h and 124.6% compared to maceration performed for 3 days. However, the highly polar flavonoid apigenin-7-glucoside was not extracted by 100% CO2 (recovery values < 1.1%). Its extraction efficiency was markedly improved by the addition of the polar modifier methanol (5%, v/v) to the CO2 fluid, yet the obtained recoveries were unsatisfactory (14.6-19.5%). The SFE method was scaled-up for preparative applications using a pilot plant with three separation stages operating in series. Large-scale SFE was technically feasible with pure CO2 as the extracting fluid. However, the use of CO2 modified with organic solvents was not effective at the pilot-plant scale.