Supercritical fluid extraction of limonoids and naringin from grapefruit (Citrus paradisi Macf.) seeds

Limonoids and naringin were extracted from grapefruit (Citrus paradisi Macf.) seeds by a supercritical carbon dioxide (SC-CO2) extraction technique. Prominent limonoids such as limonin and limonin-17-β-d-glucopyranoside (LG) and flavonoid naringin were quantified for process optimization. Extraction was completed in two stages. In stage one less polar limonin was extracted using SC-CO2 while in stage two extraction of high polar LG and naringin were completed using SC-CO2 modified by ethanol as co-solvent. Extraction parameters were studied using Box–Behnken experiment design. Response surface analysis (RSA) of the data was completed to determine effects of variables on extraction efficiency. Highest yield of limonin (6.3 mg/g seeds) was achieved at 48.3 MPa pressure, 50 °C temperature and 60 min of extraction time where as highest yield of LG (0.62 mg/g seeds) was achieved at 41.4 MPa pressure, 60 °C temperature and 30% ethanol concentration in 40 min. Highest yield of naringin (0.2 mg/g seeds) was achieved at 41.4 MPa pressure, 50 °C temperature and 20% ethanol concentration in 40 min. In all the experiments, mobile phase flow rate was kept constant at 5.0 L/min. The results demonstrated environmentally friendly, practical application of supercritical CO2 extraction of limonoids and flavonoids from grapefruit seeds.