Supercritical fluids extraction and anti-solvent purification of carotenoids from microalgae and associated bioactivity

This study investigated co-solvent modified supercritical carbon dioxide extraction of lipids and carotenoids from the microalgal species of Nannochloropsis oculata. Supercritical carbon dioxide (SCCO2) anti-solvent precipitation of carotenoids from the extracts following purification of Zeaxanthin was also examined. Continuous modification by ethanol of supercritical carbon dioxide extractions showed that the addition ratio was important for extraction efficiency of lipids and carotenoids. SCCO2 extraction at 350 bar, 323 K and 16.7 wt% of ethanol addition yielded 239.7 mg of triglycerides and 7.61 mg of carotenoids per gram extract with a total yield of 15.5%. SCCO2 anti-solvent experiments showed that the content of Zeaxanthin in the precipitate was greater than that in the fraction of normal phase column chromatography. The purest Zeaxanthin (93.8%) was then successfully isolated from the purified fraction by using a reverse-phase HPLC column chromatography. Rat macrophages treated by ultra-sonicated water extracts of the SCCO2 defatted algae showed a positive phagocytotic activity.