Compressed CO₂ Technologies for the Recovery of Carotenoid-Enriched Extracts from Dunaliella salina with Potential Neuroprotective Activity

Natural carotenoids from microalgae have attracted huge interest for their potential health benefits. Among microalgae species with high carotenoid content, Dunaliella salina has been highlighted since it is able to accumulate relatively high amounts of β-carotene and other carotenoids of industrial interest when grown under specific conditions. In the present contribution, extractions based on carbon dioxide under sub- and supercritical conditions have been optimized to improve the recovery of carotenoids and extract purity from D. salina. An experimental design was employed to investigate the effect of pressure and temperature variations ranging from 250 to 400 bar and from 15 to 45 °C, respectively. The chemical characterization of the carotenoid extracts was carried out by high-performance liquid chromatography with diode-array detection (HPLC–DAD). Moreover, inhibition of the acetylcholinesterase activity of all of the extracts was measured using a recently developed in vitro fluorescence methodology. High carotenoid yield and purity were obtained at 302–313 bar and 45 °C. Nine carotenoids were identified and three other compounds were recognized as carotenoids and quantified. Acetylcholinesterase activity inhibition could be satisfactorily explained by a partial least-squares model (63% explained variance in cross-validation) built considering the chemical composition of the different extracts. The model indicates a positive effect of lutein and 15-cis-β-carotene, the negative effect of zeaxanthin and cryptoxanthin, and the ratio of 9-cis-β-carotene/all-trans-β-carotene and 9-cis-β-carotene/total carotenoids in the inhibition of acetylcholinesterase enzyme.