Optimization of the Extraction of Antioxidants from Dunaliella salina Microalga by Pressurized Liquids

Abstract

In this work, extraction of antioxidant compounds from Dunaliella salina microalga is optimized by\ud combining pressurized liquid extraction (PLE) and experimental design (three-level factorial design)\ud with three different solvents (hexane, ethanol, and water). Two main factors were considered, the\ud extraction temperature (40, 100, and 160 °C) and the extraction time (5, 17.5, and 30 min). As response\ud variables, the extraction yield (percent dry weight/initial weight) and the antioxidant activity of the\ud extracts (determined using the TEAC method) were used. The parameters of the model were estimated\ud by multiple linear regression. Results showed that the extraction temperature was the factor having\ud the strongest influence (positive) on the two response variables. The best yields were obtained with\ud ethanol at the higher extraction temperature and time tested. Besides, although hexane extracts\ud provided the best antioxidant activity, ethanol extracts were also very active. The chemical\ud characterization of ethanol extracts was carried out using HPLC-DAD, and attempts have been made\ud to correlate their chemical composition with the antioxidant activity measured. Results pointed out\ud that the extracts contained, besides all-trans-â-carotene and isomers, several different minor\ud carotenoids that seemed to make a contribution to the antioxidant activity of the extracts.M.H. thanks the Spanish Ministry\ud of Science for a FPI grant. We thank the Ministerio de Educacio´n y\ud Ciencia (Projects AGL2002-04621-C02-02 and AGL2005-06726-C04-\ud 02) and Comunidad Auto´noma de Madrid (Project S-0505/AGR/\ud 000153) for financial support.Peer reviewe