Supercritical fluid extraction of quercetin from onion skins

Supercritical fluid extraction with ethanol-modified carbon dioxide of quercetin from onion skins (red and yellow varieties) was studied. Static and dynamic modes were investigated as extraction methods, with the static mode yielding the highest amount of quercetin recovered. The total amount of 0.024 g of quercetin per kg of onion skin was obtained for the red variety, and 0.020 g per kg for the yellow variety, at 5700 psi, 40°C, an average of 7.6% (molar concentration) of ethanol, and in an extraction period of 2.5 h.; The extraction of pure quercetin from spiked diatomaceous earth was also investigated, extraction conditions were the same as for the onion skins. A maximum of 0.036 g of quercetin per kg of matrix was extracted.; The modifier was found to have an important influence on quercetin recovery. The greater the amount of ethanol collected in the trap, the greater the amount of quercetin recovered. This trend was found for both varieties and for the pure quercetin.; Identification and quantification analysis were conducted in a High Performance Liquid Chromatography system.