Determination of lutein and zeaxanthin and antioxidant capacity of supercritical carbon dioxide extract from daylily (Hemerocallis disticha)

Lutein and zeaxanthin were extracted from daylily (Hemerocallis disticha) flowers using supercritical fluid extraction-carbon dioxide (SFE-CO2) at a temperature range of 50–95 °C and pressure range of 300–600 bar. The extracts were analysed by HPLC with a C30 column and an isocratic solvent system: methanol/methyl-tert-butyl ether = 86/14 (v/v). Moreover, the antioxidant capacities of the extracts were evaluated by a 2,2-diphenyl-2-picrylhydrazyl radical scavenging assay and a chemiluminescence assay to measure the scavenging activity of hydrogen peroxide, superoxide anion and hydroxyl radical. The optimal lutein and zeaxanthin extraction could be achieved at 80 °C and 600 bar, and the extraction pressure was the most important parameter for SFE-CO2. In addition, the extracts had significantly higher antioxidant activities in all antioxidant assays.