This study deals with supercritical CO 2 extraction of astaxanthin from Haematococcus pluVialis with ethanol as an entrainer. The effects of pressure, temperature, CO 2 flow rate, and the existence of the entrainer concentration on the amount of total extract, the amount of astaxanthin extracted, and the astaxanthin content in the extract were studied. Extractions were carried out at the pressures of 20-55 MPa, temperatures of 313-353 K, CO 2 flow rates of 2-4 mL/min, and the ethanol entrainer concentrations of 1.67-7.5% (v/v). The amount of the total extract, astaxanthin extracted, and astaxanthin content in the extract increased with increasing temperature and pressure. With higher CO 2 flow rate, the amount of the total extract could be increased while the amount of astaxanthin extracted and the astaxanthin content in the extract almost did not change. By using ethanol as an entrainer, a higher amount of astaxanthin extracted (80.6%) could be obtained at moderate pressure and temperature, and with the same conditions, the addition of the ethanol entrainer could more than twice enhance the amount of astaxanthin extracted. Without the ethanol entrainer, the highest astaxanthin extracted and astaxanthin content in the extract were 77.9 and 12.3%, respectively, and were obtained at high pressure and temperature.

This study investigated the use of ultrasound-assisted extraction (UAE) to improve the extraction efficiency of the classical solvent extraction techniques such as maceration and soxhlet extraction to extract anti-oxidant activity compounds, anthraquinones, from the root of Morinda citrifolia. The effects of different extraction conditions were determined, i.e., temperature of (25, 45, 60 degrees C), ultrasonic power, solvent types, and compositions of ethanol in ethanol-water mixtures. The results show that the yield increases with increasing extraction times and extraction temperatures. The percent recovery of anthraquinones using ultrasound was found to be highly dependent on the type of solvents (acetone > acetonitrile > methanol > ethanol). Furthermore, the use of ethanol-water solution as extraction solvent increased the yield of anthraquinones due to the relative polarity, the swelling effect of plant tissue matrix by water, and increased sound absorption. To achieve the same recovery as that achieved by UAE, soxhlet extraction and maceration required much longer time.

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