This work studied concentration enhancement of omega-3 fatty acids extracted from soft-shelled turtle fish (Pelodiscus sinensis) oil bags by using supercritical carbon dioxide (SC-CO2). Crude oil was obtained by using top-down pressurized carbon dioxide extraction at 60 bar and 328K. Crude oil was then ethylated and concentrated using a counter-current SC-CO2 extractive distillation at 200 bar and 353 K. 81 wt% of unsaturated fatty acids (i.e. C20-24) of this ethylated oil was successfully obtained in the raffinate of the distillation. The reflux flow rate, the carbon dioxide-to-oil ratio and the extraction temperature were found to be important in affecting this concentration of the C20-24. The colurnti-height versus concentration of C20-24 was examined using the Riccati equation. Furthermore, the catalase activity of rat macrophage RAW 264.7 treated with the SC-CO2 raffinate was investigated. (C) 2008 Elsevier B.V. All rights reserved.