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The effects of extraction methods (including maceration, microwave, ultrasound and magnetic field assisted extraction) and solvent evaporation methods (including water bath evaporation, vacuum freezing, vacuum and oven drying) on antioxidant activity of astaxanthin from H. pluvialis were studied. The potential antioxidant activities of extracts and dry astaxanthin samples were measured by 2, 2-Diphenyl-1-picrylhydrazyl (DPPH·), Hydroxyl (OH·) radical scavenging activity and linoleic acid emulsion. Being compared with the antioxidant activities of astaxanthin at concentration of 25 μg/ml, the magnetic field extracts and sample by treated water bath evaporation showed the highest DPPH radical scavenging activity of 60.76 and 57.6%, respectively. While magnetic field extract and vacuum freeze-drying sample of astaxanthin showed the highest hydroxyl radical scavenging activity of 18.8 and 16.78%, respectively. The results were found to be significantly higher than the other methods processed samples of the respective varieties (p <0.05). All extracts and drying samples exhibited good antioxidant activity against the linoleic acid emulsion system (p < 0.05). [ABSTRACT FROM AUTHOR]